| 1 | /* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *\ |
| 2 | * This is GNU Go, a Go program. Contact gnugo@gnu.org, or see * |
| 3 | * http://www.gnu.org/software/gnugo/ for more information. * |
| 4 | * * |
| 5 | * Copyright 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, * |
| 6 | * 2008 and 2009 by the Free Software Foundation. * |
| 7 | * * |
| 8 | * This program is free software; you can redistribute it and/or * |
| 9 | * modify it under the terms of the GNU General Public License as * |
| 10 | * published by the Free Software Foundation - version 3 or * |
| 11 | * (at your option) any later version. * |
| 12 | * * |
| 13 | * This program is distributed in the hope that it will be useful, * |
| 14 | * but WITHOUT ANY WARRANTY; without even the implied warranty of * |
| 15 | * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the * |
| 16 | * GNU General Public License in file COPYING for more details. * |
| 17 | * * |
| 18 | * You should have received a copy of the GNU General Public * |
| 19 | * License along with this program; if not, write to the Free * |
| 20 | * Software Foundation, Inc., 51 Franklin Street, Fifth Floor, * |
| 21 | * Boston, MA 02111, USA. * |
| 22 | \* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */ |
| 23 | |
| 24 | #include "gnugo.h" |
| 25 | |
| 26 | #include <stdio.h> |
| 27 | #include <stdlib.h> |
| 28 | #include <stdarg.h> |
| 29 | #include <string.h> |
| 30 | |
| 31 | #include "liberty.h" |
| 32 | #include "cache.h" |
| 33 | #include "gg_utils.h" |
| 34 | |
| 35 | /* If nonzero, attack() and find_defense() write all results to |
| 36 | * stderr. Use this to if you have deviations in results, but cannot |
| 37 | * find where they come from. |
| 38 | * |
| 39 | * Redirect results to a file. Take dumps of two versions and |
| 40 | * (assuming GNU tools) do `sort -t= -s' on both. Then join the |
| 41 | * sorted dumps: |
| 42 | * |
| 43 | * join -t= sorted-first-dump sorted-second-dump \ |
| 44 | * | sed -e "s/^[^=]\+=\([^=]\+\)=\1$//" | tr -s "\n" | tr = "\t" \ |
| 45 | * | uniq |
| 46 | * |
| 47 | * to get a nice list of deviations. This is only meaningful if you |
| 48 | * dump results of a single test (or at least tests originating at a |
| 49 | * same position). |
| 50 | */ |
| 51 | #define DUMP_ALL_RESULTS 0 |
| 52 | |
| 53 | |
| 54 | /* Size of array where candidate moves are stored. */ |
| 55 | #define MAX_MOVES 50 |
| 56 | |
| 57 | /* Please notice that message had better be a fixed string. Only the |
| 58 | * pointer to it is saved and there is no attempt to free up any |
| 59 | * storage. |
| 60 | */ |
| 61 | #define ADD_CANDIDATE_MOVE(move, this_score, moves, this_message) \ |
| 62 | do { \ |
| 63 | int u; \ |
| 64 | for (u = 0; u < (moves).num; u++) \ |
| 65 | if ((moves).pos[u] == (move)) { \ |
| 66 | (moves).score[u] += this_score; \ |
| 67 | break; \ |
| 68 | } \ |
| 69 | if ((u == (moves).num) && ((moves).num < MAX_MOVES)) { \ |
| 70 | (moves).pos[(moves).num] = move; \ |
| 71 | (moves).score[(moves).num] = this_score; \ |
| 72 | (moves).message[(moves).num] = this_message; \ |
| 73 | (moves).num++; \ |
| 74 | } \ |
| 75 | } while (0) |
| 76 | |
| 77 | #define REMOVE_CANDIDATE_MOVE(move, moves) \ |
| 78 | do { \ |
| 79 | int u; \ |
| 80 | for (u = (moves).num_tried; u < (moves).num; u++) { \ |
| 81 | if ((moves).pos[u] == (move)) { \ |
| 82 | (moves).pos[u] = (moves).pos[(moves).num - 1]; \ |
| 83 | (moves).score[u] = (moves).score[(moves).num - 1]; \ |
| 84 | (moves).message[u] = (moves).message[(moves).num - 1]; \ |
| 85 | (moves).num--; \ |
| 86 | break; \ |
| 87 | } \ |
| 88 | } \ |
| 89 | } while (0) |
| 90 | |
| 91 | |
| 92 | /* This macro checks whether the reported result is a loss, so we have won |
| 93 | * and can exit, or else if it is the best result so far. |
| 94 | * Note that SGFTRACE must have been setup. |
| 95 | */ |
| 96 | #define CHECK_RESULT(savecode, savemove, code, move_pos, move_ptr, \ |
| 97 | trace_message) \ |
| 98 | do { \ |
| 99 | if (code == 0) { \ |
| 100 | if (move_ptr) \ |
| 101 | *(move_ptr) = (move_pos); \ |
| 102 | SGFTRACE(move_pos, WIN, trace_message); \ |
| 103 | return WIN; \ |
| 104 | } \ |
| 105 | else if (REVERSE_RESULT(code) > savecode) { \ |
| 106 | savemove = move_pos; \ |
| 107 | savecode = REVERSE_RESULT(code); \ |
| 108 | } \ |
| 109 | } while (0) |
| 110 | |
| 111 | /* Reverse of CHECK_RESULT, for results passed from a helper function. */ |
| 112 | #define CHECK_RESULT_UNREVERSED(savecode, savemove, code, move_pos, \ |
| 113 | move_ptr, trace_message) \ |
| 114 | CHECK_RESULT(savecode, savemove, REVERSE_RESULT(code), move_pos, \ |
| 115 | move_ptr, trace_message) |
| 116 | |
| 117 | |
| 118 | #define RETURN_RESULT(savecode, savemove, move_ptr, trace_message) \ |
| 119 | do { \ |
| 120 | if (savecode) { \ |
| 121 | if (move_ptr) \ |
| 122 | *(move_ptr) = (savemove); \ |
| 123 | SGFTRACE(savemove, savecode, trace_message); \ |
| 124 | } \ |
| 125 | else \ |
| 126 | SGFTRACE(0, 0, NULL); \ |
| 127 | return savecode; \ |
| 128 | } while (0) |
| 129 | |
| 130 | |
| 131 | /* Play a collected batch of moves and see if any of them works. This |
| 132 | * is a defense version. |
| 133 | */ |
| 134 | #define DEFEND_TRY_MOVES(no_deep_branching, attack_hint) \ |
| 135 | do { \ |
| 136 | int k; \ |
| 137 | \ |
| 138 | for (k = moves.num_tried; k < moves.num; k++) { \ |
| 139 | int ko_move; \ |
| 140 | int dpos = moves.pos[k]; \ |
| 141 | \ |
| 142 | if (komaster_trymove(dpos, color, moves.message[k], str, &ko_move,\ |
| 143 | stackp <= ko_depth && savecode == 0)) { \ |
| 144 | int acode = do_attack(str, (attack_hint)); \ |
| 145 | popgo(); \ |
| 146 | \ |
| 147 | if (!ko_move) { \ |
| 148 | CHECK_RESULT(savecode, savemove, acode, dpos, move, \ |
| 149 | "defense effective"); \ |
| 150 | } \ |
| 151 | else { \ |
| 152 | if (acode != WIN) { \ |
| 153 | savemove = dpos; \ |
| 154 | savecode = KO_B; \ |
| 155 | } \ |
| 156 | } \ |
| 157 | } \ |
| 158 | \ |
| 159 | if ((no_deep_branching) && stackp >= branch_depth) \ |
| 160 | RETURN_RESULT(savecode, savemove, move, "branching limit"); \ |
| 161 | } \ |
| 162 | \ |
| 163 | moves.num_tried = moves.num; \ |
| 164 | } while (0) |
| 165 | |
| 166 | |
| 167 | /* Attack version of the macro above. This one is a bit more |
| 168 | * complicated, because when defender fails to defend, attacker has to |
| 169 | * prove that he can capture the string before claiming victory. |
| 170 | */ |
| 171 | #define ATTACK_TRY_MOVES(no_deep_branching, defense_hint) \ |
| 172 | do { \ |
| 173 | int k; \ |
| 174 | \ |
| 175 | for (k = moves.num_tried; k < moves.num; k++) { \ |
| 176 | int ko_move; \ |
| 177 | int apos = moves.pos[k]; \ |
| 178 | \ |
| 179 | if ((board_ko_pos != NO_MOVE || !send_two_return_one(apos, other))\ |
| 180 | && komaster_trymove(apos, other, moves.message[k], \ |
| 181 | str, &ko_move, \ |
| 182 | stackp <= ko_depth && savecode == 0)) { \ |
| 183 | int dcode = do_find_defense(str, (defense_hint)); \ |
| 184 | \ |
| 185 | if (REVERSE_RESULT(dcode) > savecode \ |
| 186 | && do_attack(str, NULL)) { \ |
| 187 | if (!ko_move) { \ |
| 188 | if (dcode == 0) { \ |
| 189 | popgo(); \ |
| 190 | RETURN_RESULT(WIN, apos, move, "attack effective"); \ |
| 191 | } \ |
| 192 | \ |
| 193 | savemove = apos; \ |
| 194 | savecode = REVERSE_RESULT(dcode); \ |
| 195 | } \ |
| 196 | else { \ |
| 197 | savemove = apos; \ |
| 198 | savecode = KO_B; \ |
| 199 | } \ |
| 200 | } \ |
| 201 | \ |
| 202 | popgo(); \ |
| 203 | } \ |
| 204 | \ |
| 205 | if ((no_deep_branching) && stackp >= branch_depth) \ |
| 206 | RETURN_RESULT(savecode, savemove, move, "branching limit"); \ |
| 207 | } \ |
| 208 | \ |
| 209 | moves.num_tried = moves.num; \ |
| 210 | } while (0) |
| 211 | |
| 212 | |
| 213 | |
| 214 | struct reading_moves |
| 215 | { |
| 216 | int pos[MAX_MOVES]; |
| 217 | int score[MAX_MOVES]; |
| 218 | const char *message[MAX_MOVES]; |
| 219 | int num; |
| 220 | int num_tried; |
| 221 | }; |
| 222 | |
| 223 | /* |
| 224 | * The functions in reading.c are used to read whether groups |
| 225 | * can be captured or not. See the Texinfo documentation |
| 226 | * (Reading) for more information. |
| 227 | * |
| 228 | * NULL POINTERS: Many functions in this file can use pointers |
| 229 | * to return the locations of recommended plays. These can be |
| 230 | * set NULL in which case these values are not returned. |
| 231 | */ |
| 232 | |
| 233 | static int do_find_defense(int str, int *move); |
| 234 | static int defend1(int str, int *move); |
| 235 | static int defend2(int str, int *move); |
| 236 | static int defend3(int str, int *move); |
| 237 | static int defend4(int str, int *move); |
| 238 | static void special_rescue_moves(int str, int lib, |
| 239 | struct reading_moves *moves); |
| 240 | static void bamboo_rescue_moves(int str, int num_libs, int libs[], |
| 241 | struct reading_moves *moves); |
| 242 | static void special_rescue2_moves(int str, int libs[2], |
| 243 | struct reading_moves *moves); |
| 244 | static void special_rescue3_moves(int str, int libs[3], |
| 245 | struct reading_moves *moves); |
| 246 | static void special_rescue4_moves(int str, int libs[2], |
| 247 | struct reading_moves *moves); |
| 248 | static void hane_rescue_moves(int str, int libs[4], |
| 249 | struct reading_moves *moves); |
| 250 | static void special_rescue5_moves(int str, int libs[3], |
| 251 | struct reading_moves *moves); |
| 252 | static void special_rescue6_moves(int str, int libs[3], |
| 253 | struct reading_moves *moves); |
| 254 | static void set_up_snapback_moves(int str, int lib, |
| 255 | struct reading_moves *moves); |
| 256 | static void edge_clamp_moves(int str, struct reading_moves *moves); |
| 257 | static int do_attack(int str, int *move); |
| 258 | static int attack1(int str, int *move); |
| 259 | static int attack2(int str, int *move); |
| 260 | static int attack3(int str, int *move); |
| 261 | static int attack4(int str, int *move); |
| 262 | static void find_cap_moves(int str, struct reading_moves *moves); |
| 263 | static void special_attack2_moves(int str, int libs[2], |
| 264 | struct reading_moves *moves); |
| 265 | static void special_attack3_moves(int str, int libs[2], |
| 266 | struct reading_moves *moves); |
| 267 | static void special_attack4_moves(int str, int libs[2], |
| 268 | struct reading_moves *moves); |
| 269 | static void draw_back_moves(int str, struct reading_moves *moves); |
| 270 | static void edge_closing_backfill_moves(int str, int apos, |
| 271 | struct reading_moves *moves); |
| 272 | static void edge_block_moves(int str, int apos, |
| 273 | struct reading_moves *moves); |
| 274 | static void propose_edge_moves(int str, int *libs, int liberties, |
| 275 | struct reading_moves *moves, int color); |
| 276 | static void break_chain_moves(int str, struct reading_moves *moves); |
| 277 | static int defend_secondary_chain1_moves(int str, struct reading_moves *moves, |
| 278 | int min_liberties); |
| 279 | static void defend_secondary_chain2_moves(int str, struct reading_moves *moves, |
| 280 | int min_liberties); |
| 281 | static void break_chain2_efficient_moves(int str, |
| 282 | struct reading_moves *moves); |
| 283 | static void do_find_break_chain2_efficient_moves(int str, int adj, |
| 284 | struct reading_moves *moves); |
| 285 | static void break_chain2_moves(int str, struct reading_moves *moves, |
| 286 | int require_safe, int be_aggressive); |
| 287 | static void break_chain2_defense_moves(int str, struct reading_moves *moves, |
| 288 | int be_aggressive); |
| 289 | static void break_chain3_moves(int str, struct reading_moves *moves, |
| 290 | int be_aggressive); |
| 291 | static void break_chain4_moves(int str, struct reading_moves *moves, |
| 292 | int be_aggressive); |
| 293 | static void superstring_moves(int str, struct reading_moves *moves, |
| 294 | int liberty_cap, int does_attack); |
| 295 | static void squeeze_moves(int str, struct reading_moves *moves); |
| 296 | static void superstring_break_chain_moves(int str, int liberty_cap, |
| 297 | struct reading_moves *moves); |
| 298 | static void double_atari_chain2_moves(int str, |
| 299 | struct reading_moves *moves, |
| 300 | int generate_more_moves); |
| 301 | static void order_moves(int str, struct reading_moves *moves, |
| 302 | int color, const char *funcname, int killer); |
| 303 | static int simple_ladder_defend(int str, int *move); |
| 304 | static int in_list(int move, int num_moves, int *moves); |
| 305 | |
| 306 | |
| 307 | /* Statistics. */ |
| 308 | static int reading_node_counter = 0; |
| 309 | static int nodes_when_called = 0; |
| 310 | |
| 311 | |
| 312 | |
| 313 | /* ================================================================ */ |
| 314 | /* Goal functions */ |
| 315 | /* ================================================================ */ |
| 316 | |
| 317 | |
| 318 | /* |
| 319 | * These functions define goals for the reading process. They use |
| 320 | * the rest of the reading machinery to evaluate whether the goal |
| 321 | * is fulfillable. |
| 322 | * |
| 323 | * The simplest goals are defined by attack() and find_defense(), |
| 324 | * namely to see if it is possible to capture or defend a single |
| 325 | * string. More complex goals are defined by e.g. attack_either() |
| 326 | * or defend_both(). |
| 327 | * |
| 328 | * The functions in this section and the next are the only ones which are |
| 329 | * callable from outside this file. |
| 330 | */ |
| 331 | |
| 332 | |
| 333 | /* attack(str, *move) determines if the string at (str) can be |
| 334 | * captured, and if so, (*move) returns the attacking move, unless |
| 335 | * (move) is a null pointer. Use a null pointer if you are interested |
| 336 | * in the result of the attack but not the attacking move itself. |
| 337 | * |
| 338 | * Return WIN if the attack succeeds unconditionally, 0 if it doesn't. |
| 339 | * Returns KO_A or KO_B if the result depends on ko: |
| 340 | * - Returns KO_A if the attack succeeds provided attacker is willing to |
| 341 | * ignore any ko threat (the attacker makes the first ko capture). |
| 342 | * - Returns KO_B if attack succeeds provided attacker has a ko threat |
| 343 | * which must be answered (the defender makes the first ko capture). |
| 344 | */ |
| 345 | |
| 346 | int |
| 347 | attack(int str, int *move) |
| 348 | { |
| 349 | int result; |
| 350 | int nodes; |
| 351 | int origin; |
| 352 | int the_move = NO_MOVE; |
| 353 | int liberties = countlib(str); |
| 354 | |
| 355 | nodes_when_called = reading_node_counter; |
| 356 | /* Don't even spend time looking in the cache if there are more than |
| 357 | * enough liberties. We need this before the persistent cache lookup |
| 358 | * to avoid results inconsistent with find_defense(). |
| 359 | */ |
| 360 | if (liberties > 4 |
| 361 | || (liberties == 4 && stackp > fourlib_depth) |
| 362 | || (liberties == 3 && stackp > depth)) |
| 363 | return 0; |
| 364 | |
| 365 | origin = find_origin(str); |
| 366 | if (search_persistent_reading_cache(ATTACK, origin, &result, &the_move)) { |
| 367 | if (move) |
| 368 | *move = the_move; |
| 369 | return result; |
| 370 | } |
| 371 | |
| 372 | memset(shadow, 0, sizeof(shadow)); |
| 373 | result = do_attack(str, &the_move); |
| 374 | nodes = reading_node_counter - nodes_when_called; |
| 375 | |
| 376 | if (debug & DEBUG_READING_PERFORMANCE) { |
| 377 | if (reading_node_counter - nodes_when_called |
| 378 | >= MIN_READING_NODES_TO_REPORT) { |
| 379 | if (result != 0) |
| 380 | gprintf("%oattack %1m(%1m) = %d %1M, %d nodes ", str, origin, result, |
| 381 | the_move, nodes); |
| 382 | else |
| 383 | gprintf("%oattack %1m(%1m) = %d, %d nodes ", str, origin, result, |
| 384 | nodes); |
| 385 | dump_stack(); |
| 386 | } |
| 387 | } |
| 388 | |
| 389 | store_persistent_reading_cache(ATTACK, origin, result, the_move, nodes); |
| 390 | |
| 391 | if (move) |
| 392 | *move = the_move; |
| 393 | |
| 394 | #if DUMP_ALL_RESULTS |
| 395 | do_dump_stack(); |
| 396 | gprintf("%oattack %1m (%d)=%d %1m\n", str, depth, result, the_move); |
| 397 | #endif |
| 398 | |
| 399 | return result; |
| 400 | } |
| 401 | |
| 402 | |
| 403 | /* find_defense(str, *move) attempts to find a move that will save |
| 404 | * the string at (str). It returns WIN if such a move is found, with |
| 405 | * (*move) the location of the saving move, unless (move) is a |
| 406 | * null pointer. It is not checked that tenuki defends, so this may |
| 407 | * give an erroneous answer if !attack(str). |
| 408 | * |
| 409 | * Returns KO_A or KO_B if the result depends on ko. Returns KO_A if the |
| 410 | * string can be defended provided the defender is willing to ignore |
| 411 | * any ko threat. Returns KO_B if the defender wins by having a ko threat |
| 412 | * which must be answered. |
| 413 | */ |
| 414 | |
| 415 | int |
| 416 | find_defense(int str, int *move) |
| 417 | { |
| 418 | int result; |
| 419 | int nodes; |
| 420 | int origin; |
| 421 | int the_move = NO_MOVE; |
| 422 | int liberties = countlib(str); |
| 423 | |
| 424 | nodes_when_called = reading_node_counter; |
| 425 | /* Don't even spend time looking in the cache if there are more than |
| 426 | * enough liberties. |
| 427 | */ |
| 428 | if (liberties > 4 |
| 429 | || (liberties == 4 && stackp > fourlib_depth)) { |
| 430 | if (move) |
| 431 | *move = NO_MOVE; |
| 432 | return WIN; |
| 433 | } |
| 434 | |
| 435 | origin = find_origin(str); |
| 436 | if (search_persistent_reading_cache(FIND_DEFENSE, origin, |
| 437 | &result, &the_move)) { |
| 438 | if (move) |
| 439 | *move = the_move; |
| 440 | return result; |
| 441 | } |
| 442 | |
| 443 | memset(shadow, 0, sizeof(shadow)); |
| 444 | result = do_find_defense(str, &the_move); |
| 445 | nodes = reading_node_counter - nodes_when_called; |
| 446 | |
| 447 | if (debug & DEBUG_READING_PERFORMANCE) { |
| 448 | if (reading_node_counter - nodes_when_called |
| 449 | >= MIN_READING_NODES_TO_REPORT) { |
| 450 | if (result != 0) |
| 451 | gprintf("%odefend %1m(%1m) = %d %1M, %d nodes ", str, origin, result, |
| 452 | the_move, nodes); |
| 453 | else |
| 454 | gprintf("%odefend %1m(%1m) = %d, %d nodes ", str, origin, result, |
| 455 | nodes); |
| 456 | dump_stack(); |
| 457 | } |
| 458 | } |
| 459 | |
| 460 | store_persistent_reading_cache(FIND_DEFENSE, origin, result, |
| 461 | the_move, nodes); |
| 462 | |
| 463 | if (move) |
| 464 | *move = the_move; |
| 465 | |
| 466 | #if DUMP_ALL_RESULTS |
| 467 | do_dump_stack(); |
| 468 | gprintf("%odefend %1m (%d)=%d %1m\n", str, depth, result, the_move); |
| 469 | #endif |
| 470 | |
| 471 | return result; |
| 472 | } |
| 473 | |
| 474 | |
| 475 | /* attack_and_defend(str, &acode, &attack_point, |
| 476 | * &dcode, &defense_point) |
| 477 | * is a frontend to the attack() and find_defense() functions, which |
| 478 | * guarantees a consistent result. If a string cannot be attacked, 0 |
| 479 | * is returned and acode is 0. If a string can be attacked and |
| 480 | * defended, WIN is returned, acode and dcode are both non-zero, and |
| 481 | * (attack_point), (defense_point) both point to vertices on the board. |
| 482 | * If a string can be attacked but not defended, 0 is again returned, |
| 483 | * acode is non-zero, dcode is 0, and (attack_point) points to a vertex |
| 484 | * on the board. |
| 485 | * |
| 486 | * This function in particular guarantees that if there is an attack, |
| 487 | * it will never return (defense_point) = NO_MOVE, which means the string is |
| 488 | * safe without defense. Separate calls to attack() and find_defense() |
| 489 | * may occasionally give this result, due to irregularities introduced |
| 490 | * by the persistent reading cache. |
| 491 | */ |
| 492 | int |
| 493 | attack_and_defend(int str, |
| 494 | int *attack_code, int *attack_point, |
| 495 | int *defend_code, int *defense_point) |
| 496 | { |
| 497 | int acode = 0; |
| 498 | int apos = NO_MOVE; |
| 499 | int dcode = 0; |
| 500 | int dpos = NO_MOVE; |
| 501 | |
| 502 | acode = attack(str, &apos); |
| 503 | if (acode != 0) |
| 504 | dcode = find_defense(str, &dpos); |
| 505 | |
| 506 | ASSERT1(!(acode != 0 && dcode == WIN && dpos == NO_MOVE), str); |
| 507 | |
| 508 | if (attack_code) |
| 509 | *attack_code = acode; |
| 510 | if (attack_point) |
| 511 | *attack_point = apos; |
| 512 | if (defend_code) |
| 513 | *defend_code = dcode; |
| 514 | if (defense_point) |
| 515 | *defense_point = dpos; |
| 516 | |
| 517 | return acode != 0 && dcode != 0; |
| 518 | } |
| 519 | |
| 520 | |
| 521 | /* |
| 522 | * attack_either(astr, bstr) returns true if there is a move which |
| 523 | * guarantees that at least one of the strings (astr) and (bstr) |
| 524 | * can be captured. A typical application for this is in connection |
| 525 | * patterns, where after a cut it suffices to capture one of the cutting |
| 526 | * stones. |
| 527 | * |
| 528 | * FIXME: The current implementation only looks for uncoordinated |
| 529 | * attacks. This is insufficient to find double ataris or |
| 530 | * moves such as 'a' in positions like |
| 531 | * |
| 532 | * XOOOOOOOX |
| 533 | * XOXXOXXOX |
| 534 | * XX..a..XX |
| 535 | * --------- |
| 536 | * |
| 537 | * where neither of the threatened X stones can be captured right |
| 538 | * out. Still either can be captured by a move down to a. |
| 539 | */ |
| 540 | |
| 541 | int |
| 542 | attack_either(int astr, int bstr) |
| 543 | { |
| 544 | int asuccess = 0; |
| 545 | int bsuccess = 0; |
| 546 | int color = board[astr]; |
| 547 | ASSERT1(IS_STONE(color) , astr); |
| 548 | ASSERT1(color == board[bstr], bstr); |
| 549 | |
| 550 | /* Start by attacking the string with the fewest liberties. On |
| 551 | * average this seems to be slightly more efficient. |
| 552 | */ |
| 553 | if (countlib(astr) > countlib(bstr)) { |
| 554 | int t = astr; |
| 555 | astr = bstr; |
| 556 | bstr = t; |
| 557 | } |
| 558 | |
| 559 | asuccess = attack(astr, NULL); |
| 560 | if (asuccess == WIN) |
| 561 | return asuccess; |
| 562 | |
| 563 | bsuccess = attack(bstr, NULL); |
| 564 | if (asuccess || bsuccess) { |
| 565 | return (asuccess > bsuccess) ? asuccess : bsuccess; |
| 566 | } |
| 567 | |
| 568 | /* Try (a little) harder */ |
| 569 | { |
| 570 | int alibs[2]; |
| 571 | int blibs[2]; |
| 572 | int alib = findlib(astr, 2, alibs); |
| 573 | int defended0 = WIN; |
| 574 | int defended1 = WIN; |
| 575 | int other = OTHER_COLOR(color); |
| 576 | /* Let's just try the case where the group with the fewest liberties |
| 577 | * has only 2, and try each atari in turn. |
| 578 | */ |
| 579 | if (alib == 2) { |
| 580 | if (trymove(alibs[0], other, "attack_either-A", astr)) { |
| 581 | defended0 = defend_both(astr, bstr); |
| 582 | popgo(); |
| 583 | } |
| 584 | if (defended0 |
| 585 | && trymove(alibs[1], other, "attack_either-B", astr)) { |
| 586 | defended1 = defend_both(astr, bstr); |
| 587 | popgo(); |
| 588 | } |
| 589 | } |
| 590 | /* The second string is possibly also short in liberties. |
| 591 | * Let's try to improve the result. |
| 592 | */ |
| 593 | if (defended0 > 0 && defended1 > 0 |
| 594 | && findlib(bstr, 2, blibs) == 2) { |
| 595 | defended0 = gg_min(defended0, defended1); |
| 596 | defended1 = defended0; |
| 597 | |
| 598 | /* We may get here even if alib==1, in case there is a snapback. |
| 599 | * To avoid referencing uninitialized memory in this case we |
| 600 | * explicitly set alibs[1] to NO_MOVE. |
| 601 | */ |
| 602 | if (alib == 1) |
| 603 | alibs[1] = NO_MOVE; |
| 604 | |
| 605 | if (blibs[0] != alibs[0] && blibs[0] != alibs[1] |
| 606 | && trymove(blibs[0], other, "attack_either-C", bstr)) { |
| 607 | int defended = defend_both(astr, bstr); |
| 608 | defended0 = gg_min(defended0, defended); |
| 609 | popgo(); |
| 610 | } |
| 611 | if (defended0 |
| 612 | && blibs[1] != alibs[0] && blibs[1] != alibs[1] |
| 613 | && trymove(blibs[1], other, "attack_either-D", bstr)) { |
| 614 | int defended = defend_both(astr, bstr); |
| 615 | defended1 = gg_min(defended1, defended); |
| 616 | popgo(); |
| 617 | } |
| 618 | } |
| 619 | return REVERSE_RESULT(gg_min(defended0, defended1)); |
| 620 | } |
| 621 | |
| 622 | } |
| 623 | |
| 624 | |
| 625 | /* |
| 626 | * defend_both(astr, bstr) returns true if both the strings (astr) |
| 627 | * and (bstr) can be defended simultaneously or if there is no attack. |
| 628 | * A typical application for this is in connection patterns, where |
| 629 | * after a cut it's necessary to defend both cutting stones. |
| 630 | * |
| 631 | * FIXME: The current implementation only makes halfhearted |
| 632 | * attempts to find coordinated defense moves. A proper implementation |
| 633 | * would require some serious reading. |
| 634 | */ |
| 635 | |
| 636 | int |
| 637 | defend_both(int astr, int bstr) |
| 638 | { |
| 639 | int a_threatened = 0; |
| 640 | int b_threatened = 0; |
| 641 | int a_savepos; |
| 642 | int b_savepos; |
| 643 | int acode = 0; |
| 644 | int dcode = 0; |
| 645 | |
| 646 | int color = board[astr]; |
| 647 | ASSERT1(IS_STONE(color) , astr); |
| 648 | ASSERT1(color == board[bstr], bstr); |
| 649 | |
| 650 | /* This probably helps here too... |
| 651 | * (see attack_either) |
| 652 | */ |
| 653 | if (countlib(astr) > countlib(bstr)) { |
| 654 | int t = astr; |
| 655 | astr = bstr; |
| 656 | bstr = t; |
| 657 | } |
| 658 | |
| 659 | attack_and_defend(astr, &acode, NULL, &dcode, &a_savepos); |
| 660 | if (acode != 0) { |
| 661 | a_threatened = 1; |
| 662 | if (dcode != WIN) |
| 663 | return 0; /* (astr) already lost */ |
| 664 | } |
| 665 | |
| 666 | attack_and_defend(bstr, &acode, NULL, &dcode, &b_savepos); |
| 667 | if (acode != 0) { |
| 668 | b_threatened = 1; |
| 669 | if (dcode != WIN) |
| 670 | return 0; /* (bstr) already lost */ |
| 671 | } |
| 672 | |
| 673 | /* Neither string can be attacked or only one of them, in which case |
| 674 | * we have time to save it. |
| 675 | */ |
| 676 | if (!a_threatened || !b_threatened) |
| 677 | return WIN; |
| 678 | |
| 679 | /* If both strings are threatened we assume that one will become lost, |
| 680 | * unless find_defense() happened to return the same defense point for |
| 681 | * both (which e.g. may happen if they are in fact the same string). |
| 682 | * This is still a bit too pessimistic, as there may be one move which |
| 683 | * saves both strings. To do this right we should try each move which |
| 684 | * defends either string and see if it also defends the other string. |
| 685 | */ |
| 686 | |
| 687 | if (a_savepos == b_savepos) |
| 688 | return WIN; /* Both strings can be attacked but also defended |
| 689 | * by one move. */ |
| 690 | |
| 691 | /* We also try each of the returned defense points and see whether |
| 692 | * the other string can still be attacked. This still gives a |
| 693 | * somewhat pessimistic estimation. |
| 694 | */ |
| 695 | |
| 696 | if (trymove(a_savepos, color, "defend_both-A", astr)) { |
| 697 | if (board[bstr] && !attack(bstr, NULL)) { |
| 698 | popgo(); |
| 699 | return WIN; |
| 700 | } |
| 701 | popgo(); |
| 702 | } |
| 703 | |
| 704 | if (trymove(b_savepos, color, "defend_both-B", bstr)) { |
| 705 | if (board[astr] && !attack(astr, NULL)) { |
| 706 | popgo(); |
| 707 | return WIN; |
| 708 | } |
| 709 | popgo(); |
| 710 | } |
| 711 | |
| 712 | /* The next improvement is to try to attack a common adjacent string. */ |
| 713 | { |
| 714 | int adjs1[MAXCHAIN]; |
| 715 | int neighbors1; |
| 716 | int adjs2[MAXCHAIN]; |
| 717 | int neighbors2; |
| 718 | int r; |
| 719 | int s; |
| 720 | int epos; |
| 721 | int fpos; |
| 722 | |
| 723 | neighbors1 = chainlinks(astr, adjs1); |
| 724 | neighbors2 = chainlinks(bstr, adjs2); |
| 725 | |
| 726 | for (r = 0; r < neighbors1; r++) { |
| 727 | epos = adjs1[r]; |
| 728 | if (countlib(epos) <= 4 |
| 729 | && (epos != a_savepos) |
| 730 | && (epos != b_savepos)) { |
| 731 | /* Is (epos) also adjacent to (bstr)? */ |
| 732 | for (s = 0; s < neighbors2; s++) { |
| 733 | if (adjs2[s] == adjs1[r]) |
| 734 | break; |
| 735 | } |
| 736 | if (s == neighbors2) |
| 737 | continue; /* No, it wasn't. */ |
| 738 | |
| 739 | if (attack(epos, &fpos)) { |
| 740 | if (trymove(fpos, color, "defend_both-C", astr)) { |
| 741 | if (board[astr] && board[bstr] |
| 742 | && !attack(astr, NULL) |
| 743 | && !attack(bstr, NULL)) { |
| 744 | popgo(); |
| 745 | return WIN; |
| 746 | } |
| 747 | popgo(); |
| 748 | } |
| 749 | } |
| 750 | } |
| 751 | } |
| 752 | } |
| 753 | |
| 754 | /* Both strings can be attacked but we have only time to defend one. */ |
| 755 | return 0; |
| 756 | } |
| 757 | |
| 758 | |
| 759 | /* |
| 760 | * break_through(apos, bpos, cpos) returns WIN if a position can |
| 761 | * succesfully be broken through and CUT if it can be cut. The position |
| 762 | * is assumed to have the shape (the colors may be reversed) |
| 763 | * |
| 764 | * .O. dbe |
| 765 | * OXO aFc |
| 766 | * |
| 767 | * It is X to move and try to capture at least one of a, b, and c. If |
| 768 | * this succeeds, X is said to have broken through the position. |
| 769 | * Otherwise X may try to cut through the position, which means |
| 770 | * keeping F safe and getting a tactically safe string at either d or |
| 771 | * e. |
| 772 | * |
| 773 | * Important notice: a, b, and c must be given in the correct order. |
| 774 | * |
| 775 | * FIXME: The reading involved here can most likely be improved. |
| 776 | * |
| 777 | * FIXME: We need to take ko results properly into account. |
| 778 | */ |
| 779 | |
| 780 | static int |
| 781 | break_through_helper(int apos, int bpos, int cpos, |
| 782 | int dpos, int epos, int Fpos, |
| 783 | int color, int other); |
| 784 | |
| 785 | int |
| 786 | break_through(int apos, int bpos, int cpos) |
| 787 | { |
| 788 | int color = board[apos]; |
| 789 | int other = OTHER_COLOR(color); |
| 790 | |
| 791 | int dpos; |
| 792 | int epos; |
| 793 | int Fpos; |
| 794 | int gpos; |
| 795 | |
| 796 | int success = 0; |
| 797 | int success2 = 0; |
| 798 | |
| 799 | /* Basic sanity checking. */ |
| 800 | ASSERT1(IS_STONE(color) , apos); |
| 801 | ASSERT1(color == board[bpos], bpos); |
| 802 | ASSERT1(color == board[cpos], cpos); |
| 803 | |
| 804 | /* Construct the rest of the points in the pattern. */ |
| 805 | Fpos = (apos + cpos) / 2; /* F midpoint between a and c. */ |
| 806 | dpos = apos + bpos - Fpos; /* Use diagonal relation a+b = d+F. */ |
| 807 | epos = bpos + cpos - Fpos; /* Use diagonal relation b+c = e+F. */ |
| 808 | |
| 809 | /* More sanity checking. */ |
| 810 | ASSERT1(board[dpos] == EMPTY , dpos); |
| 811 | ASSERT1(board[epos] == EMPTY , epos); |
| 812 | |
| 813 | /* F might already have been captured. (play_break_through_n() can't |
| 814 | * detect this. |
| 815 | */ |
| 816 | if (board[Fpos] == EMPTY) |
| 817 | return 0; |
| 818 | |
| 819 | ASSERT1(board[Fpos] == other, Fpos); |
| 820 | |
| 821 | /* First X tries to play at d. */ |
| 822 | success = break_through_helper(apos, bpos, cpos, dpos, epos, Fpos, |
| 823 | color, other); |
| 824 | if (success == WIN) |
| 825 | return WIN; |
| 826 | |
| 827 | success2 = break_through_helper(cpos, bpos, apos, epos, dpos, Fpos, |
| 828 | color, other); |
| 829 | |
| 830 | if (success2 == WIN) |
| 831 | return WIN; |
| 832 | |
| 833 | if (success2 == CUT) |
| 834 | success = CUT; |
| 835 | |
| 836 | /* If we haven't been lucky yet, we might need to start by |
| 837 | * defending F. |
| 838 | * |
| 839 | * FIXME: The function would probably be considerably faster if we |
| 840 | * start by checking whether F needs defense. Beware of ko potential |
| 841 | * though. |
| 842 | */ |
| 843 | success2 = 0; |
| 844 | if (attack_and_defend(Fpos, NULL, NULL, NULL, &gpos)) { |
| 845 | if (trymove(gpos, other, "break_through-A", Fpos)) { |
| 846 | /* Now we let O defend his position by playing either d or e. |
| 847 | * FIXME: There may be other plausible moves too. |
| 848 | */ |
| 849 | if (trymove(dpos, color, "break_through-B", Fpos)) { |
| 850 | /* O connects at d, so X cuts at e. */ |
| 851 | if (safe_move(epos, other)) { |
| 852 | success2 = CUT; |
| 853 | if (!board[cpos] || attack(cpos, NULL)) |
| 854 | success2 = WIN; |
| 855 | } |
| 856 | popgo(); |
| 857 | } |
| 858 | |
| 859 | if (success2 > 0 && trymove(epos, color, "break_through-C", Fpos)) { |
| 860 | /* O connects at e, so X cuts at d. */ |
| 861 | if (safe_move(dpos, other)) { |
| 862 | /* success2 is already WIN or CUT. */ |
| 863 | if (board[apos] && !attack(apos, NULL)) |
| 864 | success2 = CUT; |
| 865 | } |
| 866 | else |
| 867 | success2 = 0; |
| 868 | popgo(); |
| 869 | } |
| 870 | popgo(); |
| 871 | } |
| 872 | } |
| 873 | |
| 874 | if (success2 > 0) |
| 875 | return success2; |
| 876 | |
| 877 | return success; |
| 878 | } |
| 879 | |
| 880 | /* Helper function for break_through(). Since we can symmetrically |
| 881 | * start by cutting at d or e, we use the same code for both attacks, |
| 882 | * simply switching positions between the two calls. |
| 883 | */ |
| 884 | static int |
| 885 | break_through_helper(int apos, int bpos, int cpos, |
| 886 | int dpos, int epos, int Fpos, |
| 887 | int color, int other) |
| 888 | { |
| 889 | int success = 0; |
| 890 | int gpos; |
| 891 | |
| 892 | if (trymove(dpos, other, "break_through_helper-A", Fpos)) { |
| 893 | /* If F can be attacked we can't start in this way. */ |
| 894 | if (!attack(Fpos, NULL)) { |
| 895 | /* If d is safe too, we have at least managed to break through. */ |
| 896 | if (!attack(dpos, &gpos)) |
| 897 | success = CUT; |
| 898 | |
| 899 | /* Too bad, d could be attacked. We let O play the attack and |
| 900 | * then try to make a second cut at e. But first we must test if |
| 901 | * O at e is sufficient to capture d. |
| 902 | */ |
| 903 | else { |
| 904 | if (trymove(epos, color, "break_through_helper-E", Fpos)) { |
| 905 | if (!board[dpos] || !find_defense(dpos, NULL)) { |
| 906 | popgo(); |
| 907 | popgo(); |
| 908 | return 0; |
| 909 | } |
| 910 | popgo(); |
| 911 | } |
| 912 | |
| 913 | if (gpos == epos) { |
| 914 | popgo(); |
| 915 | return 0; |
| 916 | } |
| 917 | |
| 918 | if (trymove(gpos, color, "break_through_helper-F", Fpos)) { |
| 919 | if (trymove(epos, other, "break_through_helper-G", Fpos)) { |
| 920 | if (!attack(epos, NULL)) { |
| 921 | success = CUT; |
| 922 | /* Make sure b and c are safe. If not, back up & let O try |
| 923 | * to defend in a different way. */ |
| 924 | if (board[bpos] |
| 925 | && board[cpos] |
| 926 | && defend_both(bpos, cpos)) { |
| 927 | /* Can't do better than CUT. */ |
| 928 | popgo(); |
| 929 | popgo(); |
| 930 | popgo(); |
| 931 | return CUT; |
| 932 | } |
| 933 | } |
| 934 | else { |
| 935 | /* Lost everything. (Note we ignore ko at the moment.) */ |
| 936 | popgo(); |
| 937 | popgo(); |
| 938 | popgo(); |
| 939 | return 0; |
| 940 | } |
| 941 | popgo(); |
| 942 | } |
| 943 | else { |
| 944 | /* Failed to cut at all. */ |
| 945 | popgo(); |
| 946 | popgo(); |
| 947 | return 0; |
| 948 | } |
| 949 | popgo(); |
| 950 | } |
| 951 | } |
| 952 | |
| 953 | /* By now, we're sure a cut works, so now we can try |
| 954 | * to capture something. |
| 955 | */ |
| 956 | if (!board[apos] || !board[bpos] || !defend_both(apos, bpos)) |
| 957 | success = WIN; |
| 958 | else { |
| 959 | /* Both a and b could be defended, or didn't need to be. |
| 960 | * Let's see if a move at e is sufficient for O. |
| 961 | */ |
| 962 | int attack_on_b = 0; |
| 963 | int attack_on_a = 0; |
| 964 | |
| 965 | if (trymove(epos, color, "break_through_helper-B", Fpos)) { |
| 966 | if (attack(bpos, NULL)) |
| 967 | attack_on_b = 1; |
| 968 | else if (attack(apos, NULL)) |
| 969 | attack_on_a = 1; |
| 970 | popgo(); |
| 971 | } |
| 972 | |
| 973 | /* Let O find a defense and play it. */ |
| 974 | if (attack_on_a || attack_on_b) { |
| 975 | int hpos = NO_MOVE; |
| 976 | |
| 977 | if (((attack_on_a && find_defense(apos, &hpos)) |
| 978 | || (attack_on_b && find_defense(bpos, &hpos))) |
| 979 | && hpos != NO_MOVE |
| 980 | && trymove(hpos, color, "break_through_helper-C", Fpos)) { |
| 981 | /* Now we make a second cut at e, trying to capture |
| 982 | * either b or c. |
| 983 | */ |
| 984 | if (trymove(epos, other, "break_through_helper-D", Fpos)) { |
| 985 | if (!board[bpos] |
| 986 | || !board[cpos] |
| 987 | || !defend_both(bpos, cpos)) |
| 988 | success = WIN; |
| 989 | popgo(); |
| 990 | } |
| 991 | popgo(); |
| 992 | } |
| 993 | else |
| 994 | success = WIN; /* This should have been covered by |
| 995 | * defend_both(), so probably unnecessary. */ |
| 996 | } |
| 997 | } |
| 998 | } |
| 999 | popgo(); |
| 1000 | } |
| 1001 | |
| 1002 | return success; |
| 1003 | } |
| 1004 | |
| 1005 | |
| 1006 | /* ---------------------------------------------------------------- */ |
| 1007 | /* Threats */ |
| 1008 | /* ---------------------------------------------------------------- */ |
| 1009 | |
| 1010 | |
| 1011 | /* Return up to max_threats threats to capture the string at str. |
| 1012 | * If the string is directly attackable the number of threats |
| 1013 | * is reported to be 0. |
| 1014 | * |
| 1015 | * NOTE: You can call attack_threats with moves[] and codes[] |
| 1016 | * already partly filled in. So if you want to get the |
| 1017 | * threats from scratch, you have to set them to 0 |
| 1018 | * yourself. |
| 1019 | * |
| 1020 | * FIXME: Shall we report upgrades, like we can capture in ko but |
| 1021 | * have a threat to capture unconditionally? |
| 1022 | */ |
| 1023 | |
| 1024 | int |
| 1025 | attack_threats(int str, int max_points, int moves[], int codes[]) |
| 1026 | { |
| 1027 | int other; |
| 1028 | int num_threats; |
| 1029 | int liberties; |
| 1030 | int libs[MAXLIBS]; |
| 1031 | int num_adj; |
| 1032 | int adjs[MAXCHAIN]; |
| 1033 | int k; |
| 1034 | int l; |
| 1035 | int r; |
| 1036 | |
| 1037 | ASSERT1(IS_STONE(board[str]), str); |
| 1038 | other = OTHER_COLOR(board[str]); |
| 1039 | |
| 1040 | /* Only handle strings with no way to capture immediately. |
| 1041 | * For now, we treat ko the same as unconditionally. */ |
| 1042 | if (attack(str, NULL) != 0) |
| 1043 | return 0; |
| 1044 | |
| 1045 | /* This test would seem to be unnecessary since we only threaten |
| 1046 | * strings with attack_code == 0, but it turns out that single |
| 1047 | * stones with one liberty that can be captured, but come to |
| 1048 | * live again in a snap-back get attack_code == 0. |
| 1049 | * |
| 1050 | * The test against 6 liberties is just an optimization. |
| 1051 | */ |
| 1052 | liberties = findlib(str, MAXLIBS, libs); |
| 1053 | if (liberties > 1 && liberties < 6) { |
| 1054 | for (k = 0; k < liberties; k++) { |
| 1055 | int aa = libs[k]; |
| 1056 | |
| 1057 | /* Try to threaten on the liberty. */ |
| 1058 | if (trymove(aa, other, "attack_threats-A", str)) { |
| 1059 | int acode = attack(str, NULL); |
| 1060 | if (acode != 0) |
| 1061 | movelist_change_point(aa, acode, max_points, moves, codes); |
| 1062 | popgo(); |
| 1063 | } |
| 1064 | |
| 1065 | /* Try to threaten on second order liberties. */ |
| 1066 | for (l = 0; l < 4; l++) { |
| 1067 | int bb = libs[k] + delta[l]; |
| 1068 | |
| 1069 | if (!ON_BOARD(bb) |
| 1070 | || IS_STONE(board[bb]) |
| 1071 | || liberty_of_string(bb, str)) |
| 1072 | continue; |
| 1073 | |
| 1074 | if (trymove(bb, other, "attack_threats-B", str)) { |
| 1075 | int acode = attack(str, NULL); |
| 1076 | if (acode != 0) |
| 1077 | movelist_change_point(bb, acode, max_points, moves, codes); |
| 1078 | popgo(); |
| 1079 | } |
| 1080 | } |
| 1081 | } |
| 1082 | } |
| 1083 | |
| 1084 | /* Threaten to attack by saving weak neighbors. */ |
| 1085 | num_adj = chainlinks(str, adjs); |
| 1086 | for (k = 0; k < num_adj; k++) { |
| 1087 | int bb; |
| 1088 | int dd; /* Defense point of weak neighbor. */ |
| 1089 | int acode; |
| 1090 | int dcode; |
| 1091 | |
| 1092 | attack_and_defend(adjs[k], &acode, NULL, &dcode, &dd); |
| 1093 | if (acode == 0 || dcode == 0) |
| 1094 | continue; |
| 1095 | |
| 1096 | /* The strange code using r == -1 below is only avoid duplication |
| 1097 | * of the code starting with "if (trymove..)" below. |
| 1098 | * If r == -1 and stackp == 0 then use the defense point what we got from |
| 1099 | * attack_and_defend above. Otherwise step through all defense points. |
| 1100 | */ |
| 1101 | for (r = -1; r < max_points; r++) { |
| 1102 | if (stackp == 0) { |
| 1103 | if (r == -1) |
| 1104 | continue; |
| 1105 | if (worm[adjs[k]].defense_codes[r] == 0) |
| 1106 | break; |
| 1107 | bb = worm[adjs[k]].defense_points[r]; |
| 1108 | } |
| 1109 | else { |
| 1110 | if (r == -1) |
| 1111 | bb = dd; |
| 1112 | else |
| 1113 | break; |
| 1114 | } |
| 1115 | |
| 1116 | /* Test the move and see if it is a threat. */ |
| 1117 | if (trymove(bb, other, "attack_threats-C", str)) { |
| 1118 | if (board[str] == EMPTY) |
| 1119 | acode = WIN; |
| 1120 | else |
| 1121 | acode = attack(str, NULL); |
| 1122 | if (acode != 0) |
| 1123 | movelist_change_point(bb, acode, max_points, moves, codes); |
| 1124 | popgo(); |
| 1125 | } |
| 1126 | } |
| 1127 | } |
| 1128 | |
| 1129 | /* Return actual number of threats found regardless of attack code. */ |
| 1130 | if (codes[max_points - 1] > 0) |
| 1131 | return max_points; |
| 1132 | for (num_threats = 0; num_threats < max_points; num_threats++) |
| 1133 | if (codes[num_threats] == 0) |
| 1134 | break; |
| 1135 | return num_threats; |
| 1136 | } |
| 1137 | |
| 1138 | |
| 1139 | /* ================================================================ */ |
| 1140 | /* Defensive functions */ |
| 1141 | /* ================================================================ */ |
| 1142 | |
| 1143 | |
| 1144 | /* Like find_defense, but takes the komaster argument. If the |
| 1145 | * opponent is reading functions will not try |
| 1146 | * to take ko. |
| 1147 | */ |
| 1148 | |
| 1149 | static int |
| 1150 | do_find_defense(int str, int *move) |
| 1151 | { |
| 1152 | int xpos = NO_MOVE; |
| 1153 | int dcode = 0; |
| 1154 | int liberties; |
| 1155 | int retval; |
| 1156 | |
| 1157 | SETUP_TRACE_INFO("find_defense", str); |
| 1158 | |
| 1159 | /* We first check if the number of liberties is larger than four. In |
| 1160 | * that case we don't cache the result and to avoid needlessly |
| 1161 | * storing the position in the hash table, we must do this test |
| 1162 | * before we look for cached results. |
| 1163 | */ |
| 1164 | str = find_origin(str); |
| 1165 | liberties = countlib(str); |
| 1166 | |
| 1167 | if (liberties > 4 |
| 1168 | || (liberties == 4 && stackp > fourlib_depth) |
| 1169 | || (liberties == 3 && stackp > depth)) { |
| 1170 | /* No need to cache the result in these cases. */ |
| 1171 | SGFTRACE(0, WIN, "too many liberties or stackp > depth"); |
| 1172 | if (move) |
| 1173 | *move = 0; |
| 1174 | return WIN; |
| 1175 | } |
| 1176 | |
| 1177 | /* Set "killer move" up. This move (if set) was successful in |
| 1178 | * another variation, so it is reasonable to try it now. However, |
| 1179 | * we only do this if the string has at least 3 liberties - |
| 1180 | * otherwise the situation changes too much from variation to |
| 1181 | * variation. |
| 1182 | */ |
| 1183 | if (liberties > 2 && move) |
| 1184 | xpos = *move; |
| 1185 | |
| 1186 | if (stackp <= depth |
| 1187 | && tt_get(&ttable, FIND_DEFENSE, str, NO_MOVE, depth - stackp, NULL, |
| 1188 | &retval, NULL, &xpos) == 2) { |
| 1189 | /* Note that if return value is 1 (too small depth), the move will |
| 1190 | * still be used for move ordering. |
| 1191 | */ |
| 1192 | TRACE_CACHED_RESULT(retval, xpos); |
| 1193 | SGFTRACE(xpos, retval, "cached"); |
| 1194 | if (move) |
| 1195 | *move = xpos; |
| 1196 | return retval; |
| 1197 | } |
| 1198 | |
| 1199 | if (liberties == 1) |
| 1200 | dcode = defend1(str, &xpos); |
| 1201 | else if (liberties == 2) |
| 1202 | dcode = defend2(str, &xpos); |
| 1203 | else if (liberties == 3) |
| 1204 | dcode = defend3(str, &xpos); |
| 1205 | else if (liberties == 4) |
| 1206 | dcode = defend4(str, &xpos); |
| 1207 | |
| 1208 | if (dcode) { |
| 1209 | READ_RETURN(FIND_DEFENSE, str, depth - stackp, move, xpos, dcode); |
| 1210 | } |
| 1211 | |
| 1212 | READ_RETURN0(FIND_DEFENSE, str, depth - stackp); |
| 1213 | } |
| 1214 | |
| 1215 | |
| 1216 | /* Determine if a `move' by `color' allows under-the-stones tesuji |
| 1217 | * a.k.a. "big snapback". Here is an example: |
| 1218 | * |
| 1219 | * |XXXX... |
| 1220 | * |XXOOXXX |
| 1221 | * |OOOXOOX |
| 1222 | * |..O*OOX |
| 1223 | * +------- |
| 1224 | * |
| 1225 | * Even though the move at '*' allows black to capture four white |
| 1226 | * stones, white can later recapture black stones and create a second |
| 1227 | * eye. This is very similar to a snapback. |
| 1228 | * |
| 1229 | * This function returns true if a move creates a string of with two |
| 1230 | * liberties, which can, however, be instantly recaptured by opponent. |
| 1231 | * It is actually not required that the move captures something. If |
| 1232 | * the caller needs captures, it should check for them itself. |
| 1233 | */ |
| 1234 | static int |
| 1235 | allows_under_the_stones_tesuji(int move, int color) |
| 1236 | { |
| 1237 | int result = 0; |
| 1238 | SGFTree *save_sgf_dumptree; |
| 1239 | int save_count_variations; |
| 1240 | |
| 1241 | if (accuratelib(move, color, 3, NULL) != 2) |
| 1242 | return 0; |
| 1243 | |
| 1244 | save_sgf_dumptree = sgf_dumptree; |
| 1245 | save_count_variations = count_variations; |
| 1246 | |
| 1247 | sgf_dumptree = NULL; |
| 1248 | count_variations = 0; |
| 1249 | |
| 1250 | if (trymove(move, color, "allows_under_the_stones_tesuji", NO_MOVE)) { |
| 1251 | int libs[2]; |
| 1252 | |
| 1253 | findlib(move, 2, libs); |
| 1254 | if ((!is_self_atari(libs[0], color) |
| 1255 | && accuratelib(libs[1], OTHER_COLOR(color), 3, NULL) <= 2) |
| 1256 | || (!is_self_atari(libs[1], color) |
| 1257 | && accuratelib(libs[0], OTHER_COLOR(color), 3, NULL) <= 2)) |
| 1258 | result = 1; |
| 1259 | |
| 1260 | popgo(); |
| 1261 | } |
| 1262 | |
| 1263 | sgf_dumptree = save_sgf_dumptree; |
| 1264 | count_variations = save_count_variations; |
| 1265 | |
| 1266 | return result; |
| 1267 | } |
| 1268 | |
| 1269 | |
| 1270 | /* Called by the defendN functions. Don't think too much if there's |
| 1271 | * an easy way to get enough liberties. |
| 1272 | */ |
| 1273 | static int |
| 1274 | fast_defense(int str, int liberties, int *libs, int *move) |
| 1275 | { |
| 1276 | int color = board[str]; |
| 1277 | int j, k, l; |
| 1278 | int goal_liberties = (stackp < fourlib_depth ? 5 : 4); |
| 1279 | int adj, adjs[MAXCHAIN]; |
| 1280 | |
| 1281 | /* We would like to initialize liberty_mark to -1, but some |
| 1282 | * compilers warn, quite correctly, that -1 is not an unsigned |
| 1283 | * number. |
| 1284 | */ |
| 1285 | static unsigned liberty_mark = ~0U; |
| 1286 | static unsigned lm[BOARDMAX]; |
| 1287 | |
| 1288 | ASSERT1(libs != NULL, str); |
| 1289 | ASSERT1(move != NULL, str); |
| 1290 | |
| 1291 | for (k = 0; k < liberties; k++) { |
| 1292 | /* accuratelib() seems to be more efficient than fastlib() here, |
| 1293 | * probably because it catches more cases. |
| 1294 | */ |
| 1295 | if (accuratelib(libs[k], color, goal_liberties, NULL) >= goal_liberties) { |
| 1296 | *move = libs[k]; |
| 1297 | return 1; |
| 1298 | } |
| 1299 | } |
| 1300 | |
| 1301 | /* Check the cases where an opponent neighbor string is in |
| 1302 | * atari. |
| 1303 | */ |
| 1304 | adj = chainlinks2(str, adjs, 1); |
| 1305 | for (j = 0; j < adj; j++) { |
| 1306 | int lib; |
| 1307 | int missing = goal_liberties - liberties; |
| 1308 | int total = 0; |
| 1309 | int adj2, adjs2[MAXCHAIN]; |
| 1310 | int alib, alibs[MAXLIBS]; |
| 1311 | int num_adjacent_stones; |
| 1312 | |
| 1313 | findlib(adjs[j], 1, &lib); |
| 1314 | /* We aren't interested in ko (at this stage). And playing |
| 1315 | * our own last liberty to capture is prone to snapbacks, |
| 1316 | * so better let the 'normal' reading routines do the job. |
| 1317 | */ |
| 1318 | if ((liberties == 1 && lib == libs[0] |
| 1319 | && countstones(adjs[j]) <= 2) |
| 1320 | || is_ko(lib, color, NULL)) |
| 1321 | continue; |
| 1322 | |
| 1323 | /* Would the capture already gain enough liberties ? |
| 1324 | * No need to test the case if the move is one of our liberties, |
| 1325 | * it has already been done in the first loop of this function. |
| 1326 | */ |
| 1327 | num_adjacent_stones = count_adjacent_stones(adjs[j], str, missing); |
| 1328 | if (!liberty_of_string(lib, str) |
| 1329 | && num_adjacent_stones >= missing) { |
| 1330 | *move = lib; |
| 1331 | return 1; |
| 1332 | } |
| 1333 | ASSERT1(num_adjacent_stones >= 1, str); |
| 1334 | |
| 1335 | /* What is the total number of liberties of the friendly strings around |
| 1336 | * the lunch? |
| 1337 | */ |
| 1338 | if (++liberty_mark == 0) { |
| 1339 | memset(lm, 0, sizeof(lm)); |
| 1340 | liberty_mark++; |
| 1341 | } |
| 1342 | /* Loop over all neighbors of the lunch. */ |
| 1343 | adj2 = chainlinks(adjs[j], adjs2); |
| 1344 | for (k = 0; k < adj2; k++) { |
| 1345 | /* Loop over all liberties of the neighbor. */ |
| 1346 | alib = findlib(adjs2[k], MAXLIBS, alibs); |
| 1347 | for (l = 0; l < alib; l++) { |
| 1348 | if (lm[alibs[l]] != liberty_mark) { |
| 1349 | lm[alibs[l]] = liberty_mark; |
| 1350 | total++; |
| 1351 | } |
| 1352 | } |
| 1353 | } |
| 1354 | |
| 1355 | /* The captured string is treated as common liberties, and |
| 1356 | * some adjustements are made : |
| 1357 | * - we're adding a stone for capturing the lunch (-1) |
| 1358 | * - opponent might be able to remove a liberty (-1) |
| 1359 | * - and possibly force us to connect (-1) |
| 1360 | * - reduce us by one more liberty with a throw-in; this |
| 1361 | * is only possible if there is only one adjacent stone in the |
| 1362 | * lunch to the string (-1) |
| 1363 | * Probably there are more damezumari-type cases, but as a heuristic, |
| 1364 | * it seems good enough. |
| 1365 | */ |
| 1366 | total += countstones(adjs[j]) - 2; |
| 1367 | if (lm[lib] == liberty_mark) |
| 1368 | total--; |
| 1369 | if (num_adjacent_stones == 1) |
| 1370 | total--; |
| 1371 | |
| 1372 | if (total >= goal_liberties) { |
| 1373 | /* One case when this code can give a false defense is an |
| 1374 | * under-the-stones tesuji or "big snapback." See reading:199 |
| 1375 | * for an example. While this position is probably very rare, |
| 1376 | * it is nice to make GNU Go understand "neat" tesujis. |
| 1377 | */ |
| 1378 | if (liberties == 1 && lib == libs[0] |
| 1379 | && allows_under_the_stones_tesuji(lib, color)) { |
| 1380 | /* This is a bad "fast defense". */ |
| 1381 | continue; |
| 1382 | } |
| 1383 | |
| 1384 | *move = lib; |
| 1385 | return 1; |
| 1386 | } |
| 1387 | } |
| 1388 | |
| 1389 | return 0; |
| 1390 | } |
| 1391 | |
| 1392 | /* If str points to a string with exactly one liberty, defend1 |
| 1393 | * determines whether it can be saved by extending or capturing |
| 1394 | * a boundary chain having one liberty. The function returns WIN if the string |
| 1395 | * can be saved, otherwise 0. It returns KO_A or KO_B if it can be saved, |
| 1396 | * conditioned on ko. Returns KO_A if it can be saved provided (color) is |
| 1397 | * willing to ignore any ko threat. Returns KO_B if it can be saved if (color) |
| 1398 | * has a ko threat which must be answered. |
| 1399 | * |
| 1400 | * The pair defend1-attack2 call each other recursively to |
| 1401 | * read situations such as ladders. They read all ladders to the end. |
| 1402 | * If the reading ply (stackp) is deeper than the deep-reading cutoff |
| 1403 | * parameter depth, whose default value DEPTH is defined in gnugo.h, then a |
| 1404 | * string is assumed alive if it can get 3 liberties. When |
| 1405 | * fourlib_depth < stackp < depth, a string is considered alive if it can get |
| 1406 | * four liberties. When stackp < fourlib_depth, it is considered alive |
| 1407 | * if it can get 5 liberties. |
| 1408 | * */ |
| 1409 | |
| 1410 | static int |
| 1411 | defend1(int str, int *move) |
| 1412 | { |
| 1413 | int color = board[str]; |
| 1414 | int other = OTHER_COLOR(color); |
| 1415 | int xpos; |
| 1416 | int lib; |
| 1417 | struct reading_moves moves; |
| 1418 | int savemove = 0; |
| 1419 | int savecode = 0; |
| 1420 | int liberties; |
| 1421 | int k; |
| 1422 | |
| 1423 | SETUP_TRACE_INFO("defend1", str); |
| 1424 | reading_node_counter++; |
| 1425 | |
| 1426 | ASSERT1(IS_STONE(board[str]), str); |
| 1427 | ASSERT1(countlib(str) == 1, str); |
| 1428 | |
| 1429 | /* lib will be the liberty of the string. */ |
| 1430 | liberties = findlib(str, 1, &lib); |
| 1431 | ASSERT1(liberties == 1, str); |
| 1432 | |
| 1433 | if (fast_defense(str, liberties, &lib, &xpos)) |
| 1434 | RETURN_RESULT(WIN, xpos, move, "fast defense"); |
| 1435 | |
| 1436 | /* Collect moves to try in the first batch. |
| 1437 | * 1. First order liberty. |
| 1438 | * 2. Chain breaking moves. |
| 1439 | * 3. Moves to set up a snapback. |
| 1440 | */ |
| 1441 | moves.pos[0] = lib; |
| 1442 | moves.score[0] = 0; |
| 1443 | moves.message[0] = "liberty"; |
| 1444 | moves.num = 1; |
| 1445 | moves.num_tried = 0; |
| 1446 | |
| 1447 | break_chain_moves(str, &moves); |
| 1448 | set_up_snapback_moves(str, lib, &moves); |
| 1449 | |
| 1450 | order_moves(str, &moves, color, read_function_name, *move); |
| 1451 | DEFEND_TRY_MOVES(0, NULL); |
| 1452 | |
| 1453 | /* If the string is a single stone and a capture would give a ko, |
| 1454 | * try to defend it with ko by backfilling. |
| 1455 | * |
| 1456 | * FIXME: What is an example of this? Is it correct that the |
| 1457 | * return value is WIN and not KO_A or KO_B? |
| 1458 | */ |
| 1459 | if (stackp <= backfill_depth |
| 1460 | && countstones(str) == 1 |
| 1461 | && is_ko(lib, other, NULL)) { |
| 1462 | int libs2[6]; |
| 1463 | liberties = approxlib(lib, color, 6, libs2); |
| 1464 | if (liberties <= 5) { |
| 1465 | for (k = 0; k < liberties; k++) { |
| 1466 | int apos = libs2[k]; |
| 1467 | if ((liberties == 1 || !is_self_atari(apos, other)) |
| 1468 | && trymove(apos, color, "defend1-C", str)) { |
| 1469 | int acode = do_attack(str, NULL); |
| 1470 | popgo(); |
| 1471 | CHECK_RESULT(savecode, savemove, acode, apos, move, "backfilling"); |
| 1472 | } |
| 1473 | } |
| 1474 | } |
| 1475 | } |
| 1476 | |
| 1477 | RETURN_RESULT(savecode, savemove, move, "saved move"); |
| 1478 | } |
| 1479 | |
| 1480 | |
| 1481 | |
| 1482 | /* If str points to a group with two liberties, defend2 determines |
| 1483 | * whether the group can be saved by extending, or by capturing part of |
| 1484 | * its surrounding chain. A group is considered safe if either part of |
| 1485 | * the surrounding chain may be captured, or if it can get 3 |
| 1486 | * liberties. It is presumed that the opponent could kill if tenuki. |
| 1487 | * If both extensions work, it prefers the one which maximizes |
| 1488 | * liberties. |
| 1489 | * |
| 1490 | * *move returns the move to save the stones. |
| 1491 | */ |
| 1492 | |
| 1493 | static int |
| 1494 | defend2(int str, int *move) |
| 1495 | { |
| 1496 | int color, other; |
| 1497 | int xpos = NO_MOVE; |
| 1498 | int liberties; |
| 1499 | int libs[2]; |
| 1500 | int liberties2; |
| 1501 | int libs2[6]; |
| 1502 | struct reading_moves moves; |
| 1503 | int savemove = 0; |
| 1504 | int savecode = 0; |
| 1505 | int k; |
| 1506 | int r; |
| 1507 | int suggest_move = NO_MOVE; |
| 1508 | int string_size; |
| 1509 | int be_aggressive; |
| 1510 | |
| 1511 | SETUP_TRACE_INFO("defend2", str); |
| 1512 | reading_node_counter++; |
| 1513 | |
| 1514 | color = board[str]; |
| 1515 | other = OTHER_COLOR(color); |
| 1516 | |
| 1517 | ASSERT1(IS_STONE(board[str]), str); |
| 1518 | ASSERT1(countlib(str) == 2, str); |
| 1519 | |
| 1520 | liberties = findlib(str, 2, libs); |
| 1521 | |
| 1522 | if (fast_defense(str, liberties, libs, &xpos)) |
| 1523 | RETURN_RESULT(WIN, xpos, move, "fast defense"); |
| 1524 | |
| 1525 | /* Collect moves to try in the first batch. |
| 1526 | * 1. First order liberties. |
| 1527 | * 2. Chain breaking moves. |
| 1528 | * 3. Second order liberties moving up from first line to second. |
| 1529 | * 4. Edge clamps. |
| 1530 | */ |
| 1531 | moves.num = 0; |
| 1532 | moves.num_tried = 0; |
| 1533 | |
| 1534 | /* We don't want to play self-atari liberties, unless the string is a |
| 1535 | * single stone (in which case it might be a snapback move). Sacrifices |
| 1536 | * might be good moves, but not in tactical reading. |
| 1537 | */ |
| 1538 | string_size = countstones(str); |
| 1539 | if (string_size == 1 || !is_self_atari(libs[0], color)) |
| 1540 | ADD_CANDIDATE_MOVE(libs[0], 0, moves, "liberty"); |
| 1541 | if (string_size == 1 || !is_self_atari(libs[1], color)) |
| 1542 | ADD_CANDIDATE_MOVE(libs[1], 0, moves, "liberty"); |
| 1543 | |
| 1544 | break_chain_moves(str, &moves); |
| 1545 | break_chain2_efficient_moves(str, &moves); |
| 1546 | propose_edge_moves(str, libs, liberties, &moves, color); |
| 1547 | edge_clamp_moves(str, &moves); |
| 1548 | |
| 1549 | if (stackp <= depth) { |
| 1550 | for (k = 0; k < liberties; k++) |
| 1551 | special_rescue_moves(str, libs[k], &moves); |
| 1552 | bamboo_rescue_moves(str, liberties, libs, &moves); |
| 1553 | } |
| 1554 | |
| 1555 | if (stackp <= backfill_depth) |
| 1556 | special_rescue2_moves(str, libs, &moves); |
| 1557 | |
| 1558 | order_moves(str, &moves, color, read_function_name, *move); |
| 1559 | DEFEND_TRY_MOVES(0, &suggest_move); |
| 1560 | |
| 1561 | /* Look for backfilling moves. */ |
| 1562 | for (k = 0; k < liberties; k++) { |
| 1563 | if (is_self_atari(libs[k], other)) { |
| 1564 | liberties2 = approxlib(libs[k], color, 6, libs2); |
| 1565 | /* Note: liberties2 must be smaller than 5, otherwise libs[k] had been |
| 1566 | * a direct defense. |
| 1567 | */ |
| 1568 | for (r = 0; r < liberties2; r++) { |
| 1569 | xpos = libs2[r]; |
| 1570 | /* If the newly placed stone would be in atari, but not a single |
| 1571 | * stone, we don't even try. |
| 1572 | */ |
| 1573 | if (!is_self_atari(xpos, color) |
| 1574 | && has_neighbor(xpos, color)) |
| 1575 | ADD_CANDIDATE_MOVE(xpos, 0, moves, "backfill-A"); |
| 1576 | } |
| 1577 | } |
| 1578 | |
| 1579 | liberties2 = approxlib(libs[k], other, 3, libs2); |
| 1580 | if (liberties2 <= 2) { |
| 1581 | for (r = 0; r < liberties2; r++) { |
| 1582 | xpos = libs2[r]; |
| 1583 | if (!is_self_atari(xpos, color)) |
| 1584 | ADD_CANDIDATE_MOVE(xpos, 0, moves, "backfill-B"); |
| 1585 | } |
| 1586 | } |
| 1587 | } |
| 1588 | |
| 1589 | special_rescue4_moves(str, libs, &moves); |
| 1590 | |
| 1591 | /* Only order and test the new set of moves. */ |
| 1592 | order_moves(str, &moves, color, read_function_name, *move); |
| 1593 | DEFEND_TRY_MOVES(0, &suggest_move); |
| 1594 | |
| 1595 | /* If we haven't found any useful moves in first batches, be more |
| 1596 | * aggressive in break_chain[23]_moves(). |
| 1597 | */ |
| 1598 | be_aggressive = (moves.num == 0); |
| 1599 | |
| 1600 | if (stackp <= superstring_depth) |
| 1601 | superstring_break_chain_moves(str, 4, &moves); |
| 1602 | |
| 1603 | /* If nothing else works, we try playing a liberty of the |
| 1604 | * super_string. |
| 1605 | */ |
| 1606 | if (stackp <= superstring_depth) { |
| 1607 | superstring_moves(str, &moves, 3, 0); |
| 1608 | squeeze_moves(str, &moves); |
| 1609 | } |
| 1610 | |
| 1611 | break_chain2_defense_moves(str, &moves, be_aggressive); |
| 1612 | |
| 1613 | if (stackp <= backfill_depth) |
| 1614 | special_rescue5_moves(str, libs, &moves); |
| 1615 | |
| 1616 | if (stackp <= break_chain_depth |
| 1617 | || (be_aggressive && stackp <= backfill_depth)) |
| 1618 | break_chain3_moves(str, &moves, be_aggressive); |
| 1619 | |
| 1620 | if (be_aggressive && stackp <= backfill_depth) |
| 1621 | break_chain4_moves(str, &moves, be_aggressive); |
| 1622 | |
| 1623 | /* Only order and test the new set of moves. */ |
| 1624 | order_moves(str, &moves, color, read_function_name, *move); |
| 1625 | DEFEND_TRY_MOVES(0, &suggest_move); |
| 1626 | |
| 1627 | RETURN_RESULT(savecode, savemove, move, "saved move"); |
| 1628 | } |
| 1629 | |
| 1630 | |
| 1631 | /* defend3(str, *move) attempts to find a move rescuing the |
| 1632 | * string at (str) with 3 liberties. If such a move can be found, |
| 1633 | * it returns true and the saving move in *move. |
| 1634 | */ |
| 1635 | |
| 1636 | static int |
| 1637 | defend3(int str, int *move) |
| 1638 | { |
| 1639 | int color; |
| 1640 | int xpos = NO_MOVE; |
| 1641 | int liberties; |
| 1642 | int libs[3]; |
| 1643 | struct reading_moves moves; |
| 1644 | int savemove = 0; |
| 1645 | int savecode = 0; |
| 1646 | int k; |
| 1647 | int suggest_move = NO_MOVE; |
| 1648 | |
| 1649 | SETUP_TRACE_INFO("defend3", str); |
| 1650 | reading_node_counter++; |
| 1651 | |
| 1652 | color = board[str]; |
| 1653 | |
| 1654 | ASSERT1(IS_STONE(board[str]), str); |
| 1655 | ASSERT1(countlib(str) == 3, str); |
| 1656 | |
| 1657 | liberties = findlib(str, 3, libs); |
| 1658 | |
| 1659 | if (fast_defense(str, liberties, libs, &xpos)) |
| 1660 | RETURN_RESULT(WIN, xpos, move, "fast defense"); |
| 1661 | |
| 1662 | /* Collect moves to try in the first batch. |
| 1663 | * 1. First order liberties. |
| 1664 | * 2. Chain breaking moves. |
| 1665 | * 3. Second order liberties moving up from first line to second. |
| 1666 | * 4. Edge clamps. |
| 1667 | */ |
| 1668 | for (k = 0; k < liberties; k++) { |
| 1669 | moves.pos[k] = libs[k]; |
| 1670 | moves.score[k] = 0; |
| 1671 | moves.message[k] = "liberty"; |
| 1672 | } |
| 1673 | |
| 1674 | moves.num = liberties; |
| 1675 | moves.num_tried = 0; |
| 1676 | |
| 1677 | break_chain_moves(str, &moves); |
| 1678 | break_chain2_efficient_moves(str, &moves); |
| 1679 | propose_edge_moves(str, libs, liberties, &moves, color); |
| 1680 | edge_clamp_moves(str, &moves); |
| 1681 | |
| 1682 | if (stackp <= backfill2_depth) |
| 1683 | hane_rescue_moves(str, libs, &moves); |
| 1684 | |
| 1685 | order_moves(str, &moves, color, read_function_name, *move); |
| 1686 | DEFEND_TRY_MOVES(1, &suggest_move); |
| 1687 | |
| 1688 | /* This looks a little too expensive. */ |
| 1689 | #if 0 |
| 1690 | /* Look for backfilling moves. */ |
| 1691 | if (stackp <= backfill_depth) { |
| 1692 | int other = OTHER_COLOR(color); |
| 1693 | int liberties2; |
| 1694 | int libs2[6]; |
| 1695 | int r; |
| 1696 | int s; |
| 1697 | for (k = 0; k < liberties; k++) { |
| 1698 | if (is_self_atari(libs[k], other)) { |
| 1699 | liberties2 = approxlib(libs[k], color, 6, libs2); |
| 1700 | for (r = 0; r < liberties2; r++) { |
| 1701 | xpos = libs2[r]; |
| 1702 | /* Don't reconsider previously tested moves. */ |
| 1703 | for (s = 0; s < moves.num; s++) |
| 1704 | if (xpos == moves.pos[s]) |
| 1705 | break; |
| 1706 | if (s < moves.num) |
| 1707 | continue; |
| 1708 | |
| 1709 | if (trymove(xpos, color, "defend3-D", str)) { |
| 1710 | int acode; |
| 1711 | /* If the newly placed stone is in atari, we give up |
| 1712 | * without fight. |
| 1713 | */ |
| 1714 | if (countlib(xpos) == 1) |
| 1715 | acode = WIN; |
| 1716 | else |
| 1717 | acode = do_attack(str, NULL); |
| 1718 | |
| 1719 | popgo(); |
| 1720 | CHECK_RESULT(savecode, savemove, acode, xpos, move, |
| 1721 | "backfill effective"); |
| 1722 | } |
| 1723 | } |
| 1724 | } |
| 1725 | else { |
| 1726 | liberties2 = approxlib(libs[k], other, 3, libs2); |
| 1727 | if (liberties2 <= 3) { |
| 1728 | for (r = 0; r < liberties2; r++) { |
| 1729 | xpos = libs2[r]; |
| 1730 | /* Don't reconsider previously tested moves. */ |
| 1731 | for (s = 0; s < moves.num; s++) |
| 1732 | if (xpos == moves.pos[s]) |
| 1733 | break; |
| 1734 | if (s < moves.num) |
| 1735 | continue; |
| 1736 | |
| 1737 | if (!is_self_atari(xpos, color) |
| 1738 | && trymove(xpos, color, "defend2-G", str)) { |
| 1739 | int acode = do_attack(str, NULL); |
| 1740 | popgo(); |
| 1741 | CHECK_RESULT(savecode, savemove, acode, xpos, move |
| 1742 | "backfill effective"); |
| 1743 | } |
| 1744 | } |
| 1745 | } |
| 1746 | } |
| 1747 | } |
| 1748 | } |
| 1749 | #endif |
| 1750 | |
| 1751 | /* If nothing else works, try to defend with second order liberties. */ |
| 1752 | |
| 1753 | if (stackp <= backfill_depth) |
| 1754 | special_rescue3_moves(str, libs, &moves); |
| 1755 | |
| 1756 | if (stackp <= depth) { |
| 1757 | for (k = 0; k < liberties; k++) |
| 1758 | special_rescue_moves(str, libs[k], &moves); |
| 1759 | bamboo_rescue_moves(str, liberties, libs, &moves); |
| 1760 | } |
| 1761 | |
| 1762 | if (get_level() >= 8 && stackp <= backfill2_depth) |
| 1763 | superstring_break_chain_moves(str, 4, &moves); |
| 1764 | |
| 1765 | if (stackp <= break_chain_depth) |
| 1766 | break_chain2_defense_moves(str, &moves, 0); |
| 1767 | |
| 1768 | if (stackp <= backfill_depth) { |
| 1769 | special_rescue5_moves(str, libs, &moves); |
| 1770 | special_rescue6_moves(str, libs, &moves); |
| 1771 | } |
| 1772 | |
| 1773 | /* Only order and test the new set of moves. */ |
| 1774 | order_moves(str, &moves, color, read_function_name, *move); |
| 1775 | DEFEND_TRY_MOVES(1, &suggest_move); |
| 1776 | |
| 1777 | /* If nothing else works, we try playing a liberty of the |
| 1778 | * super_string. |
| 1779 | */ |
| 1780 | if (get_level() >= 8 && stackp <= backfill2_depth) { |
| 1781 | superstring_moves(str, &moves, 3, 0); |
| 1782 | squeeze_moves(str, &moves); |
| 1783 | } |
| 1784 | |
| 1785 | if (stackp <= break_chain_depth) |
| 1786 | break_chain3_moves(str, &moves, 0); |
| 1787 | |
| 1788 | /* Only order and test the new set of moves. */ |
| 1789 | order_moves(str, &moves, color, read_function_name, *move); |
| 1790 | DEFEND_TRY_MOVES(1, &suggest_move); |
| 1791 | |
| 1792 | RETURN_RESULT(savecode, savemove, move, "saved move"); |
| 1793 | } |
| 1794 | |
| 1795 | |
| 1796 | /* defend4(str, *move) attempts to find a move rescuing the |
| 1797 | * string at (str) with 4 liberties. If such a move can be found, |
| 1798 | * it returns true, and if the pointer move is not NULL, |
| 1799 | * then it returns the saving move in *move. |
| 1800 | */ |
| 1801 | |
| 1802 | static int |
| 1803 | defend4(int str, int *move) |
| 1804 | { |
| 1805 | int color; |
| 1806 | int xpos = NO_MOVE; |
| 1807 | int liberties; |
| 1808 | int libs[4]; |
| 1809 | struct reading_moves moves; |
| 1810 | int savemove = 0; |
| 1811 | int savecode = 0; |
| 1812 | int k; |
| 1813 | int suggest_move = NO_MOVE; |
| 1814 | |
| 1815 | SETUP_TRACE_INFO("defend4", str); |
| 1816 | reading_node_counter++; |
| 1817 | |
| 1818 | color = board[str]; |
| 1819 | |
| 1820 | ASSERT1(IS_STONE(board[str]), str); |
| 1821 | ASSERT1(countlib(str) == 4, str); |
| 1822 | |
| 1823 | liberties = findlib(str, 4, libs); |
| 1824 | |
| 1825 | if (fast_defense(str, liberties, libs, &xpos)) |
| 1826 | RETURN_RESULT(WIN, xpos, move, "fast defense"); |
| 1827 | |
| 1828 | /* Collect moves to try in the first batch. |
| 1829 | * 1. First order liberties. |
| 1830 | * 2. Chain breaking moves. |
| 1831 | */ |
| 1832 | for (k = 0; k < liberties; k++) { |
| 1833 | moves.pos[k] = libs[k]; |
| 1834 | moves.score[k] = 0; |
| 1835 | moves.message[k] = "liberty"; |
| 1836 | } |
| 1837 | |
| 1838 | moves.num = liberties; |
| 1839 | moves.num_tried = 0; |
| 1840 | |
| 1841 | break_chain_moves(str, &moves); |
| 1842 | break_chain2_efficient_moves(str, &moves); |
| 1843 | |
| 1844 | if (stackp <= backfill_depth) { |
| 1845 | break_chain2_defense_moves(str, &moves, 0); |
| 1846 | break_chain3_moves(str, &moves, 0); |
| 1847 | break_chain4_moves(str, &moves, 0); |
| 1848 | #if 0 |
| 1849 | hane_rescue_moves(str, libs, &moves); |
| 1850 | #endif |
| 1851 | if (stackp <= superstring_depth) |
| 1852 | superstring_moves(str, &moves, 4, 0); |
| 1853 | squeeze_moves(str, &moves); |
| 1854 | } |
| 1855 | |
| 1856 | order_moves(str, &moves, color, read_function_name, *move); |
| 1857 | DEFEND_TRY_MOVES(1, &suggest_move); |
| 1858 | |
| 1859 | if (stackp <= depth) { |
| 1860 | for (k = 0; k < liberties; k++) |
| 1861 | special_rescue_moves(str, libs[k], &moves); |
| 1862 | bamboo_rescue_moves(str, liberties, libs, &moves); |
| 1863 | } |
| 1864 | |
| 1865 | order_moves(str, &moves, color, read_function_name, *move); |
| 1866 | DEFEND_TRY_MOVES(1, &suggest_move); |
| 1867 | |
| 1868 | RETURN_RESULT(savecode, savemove, move, "saved move"); |
| 1869 | } |
| 1870 | |
| 1871 | |
| 1872 | /* |
| 1873 | * special_rescue_moves(str, lib, *move) is called with (str) a |
| 1874 | * string having a liberty at (lib). |
| 1875 | * |
| 1876 | * This adds moves on a second order liberty to the list of candidate |
| 1877 | * moves in the struct *moves; e.g. in shapes like: |
| 1878 | * |
| 1879 | * . O O X.XXO |
| 1880 | * O.* or ..* or O.* or XOOXO |
| 1881 | * O O O ...*. |
| 1882 | * ----- |
| 1883 | * |
| 1884 | * This will occasionally save a string where no other move will. To |
| 1885 | * reduce the branching caused by these moves, we require that the |
| 1886 | * opponent can be trivially captured when trying to intercept on the |
| 1887 | * corresponding first order liberty. |
| 1888 | */ |
| 1889 | |
| 1890 | static void |
| 1891 | special_rescue_moves(int str, int lib, struct reading_moves *moves) |
| 1892 | { |
| 1893 | int color = board[str]; |
| 1894 | int other = OTHER_COLOR(color); |
| 1895 | int otherlib; |
| 1896 | int k; |
| 1897 | |
| 1898 | /* Use approxlib() to test for trivial capture. */ |
| 1899 | otherlib = approxlib(lib, other, 3, NULL); |
| 1900 | if (otherlib > 2) |
| 1901 | return; |
| 1902 | |
| 1903 | /* Loop over the four neighbours of the liberty, (lib + d). */ |
| 1904 | for (k = 0; k < 4; k++) { |
| 1905 | int d = delta[k]; |
| 1906 | if (board[lib + d] == EMPTY) { |
| 1907 | |
| 1908 | /* Don't play into a self atari unless we have a potential snapback. */ |
| 1909 | if (is_self_atari(lib + d, color) && otherlib > 1) |
| 1910 | continue; |
| 1911 | |
| 1912 | /* Be more demanding when the string has four liberties. (Mostly |
| 1913 | * because attack4() otherwise would need more move generators.) |
| 1914 | * More precisely we require not only the first order liberty to |
| 1915 | * become a self atari for the opponent but also one more of the |
| 1916 | * neighbors of the proposed move. See reading:144 for a |
| 1917 | * position where we otherwise would try to defend at D9 and |
| 1918 | * attack4() then lacks move generators to stop black from |
| 1919 | * continuing towards the top left corner. |
| 1920 | */ |
| 1921 | if (countlib(str) > 3) { |
| 1922 | int r; |
| 1923 | int number_protected = 0; |
| 1924 | |
| 1925 | for (r = 0; r < 4; r++) { |
| 1926 | if (board[lib + d + delta[r]] == EMPTY |
| 1927 | && approxlib(lib + d + delta[r], other, 3, NULL) < 3) |
| 1928 | number_protected++; |
| 1929 | if (number_protected == 2) |
| 1930 | break; |
| 1931 | } |
| 1932 | |
| 1933 | if (number_protected < 2) |
| 1934 | continue; |
| 1935 | } |
| 1936 | |
| 1937 | ADD_CANDIDATE_MOVE(lib + d, 0, *moves, "special_rescue"); |
| 1938 | } |
| 1939 | } |
| 1940 | } |
| 1941 | |
| 1942 | |
| 1943 | /* |
| 1944 | * In situations like |
| 1945 | * |
| 1946 | * XXXXXO |
| 1947 | * XO.*.O |
| 1948 | * XO.O.O |
| 1949 | * XXXXXO |
| 1950 | * |
| 1951 | * playing at * is the correct rescue move, although the opponent cannot |
| 1952 | * be captured at the respective first-order liberty. |
| 1953 | */ |
| 1954 | static void |
| 1955 | bamboo_rescue_moves(int str, int num_libs, int libs[], |
| 1956 | struct reading_moves *moves) |
| 1957 | { |
| 1958 | int color = board[str]; |
| 1959 | int l1, l2; |
| 1960 | |
| 1961 | for (l1 = 0; l1 < num_libs; l1++) |
| 1962 | for (l2 = 0; l2 < num_libs; l2++) { |
| 1963 | if (l1 == l2) |
| 1964 | continue; |
| 1965 | |
| 1966 | if (libs[l1] == WEST(libs[l2]) || libs[l1] == EAST(libs[l2])) { |
| 1967 | if (board[SOUTH(libs[l1])] == EMPTY |
| 1968 | && board[SOUTH(libs[l2])] == color |
| 1969 | && !is_self_atari(SOUTH(libs[l1]), color)) |
| 1970 | ADD_CANDIDATE_MOVE(SOUTH(libs[l1]), 0, *moves, "bamboo_rescue"); |
| 1971 | if (board[NORTH(libs[l1])] == EMPTY |
| 1972 | && board[NORTH(libs[l2])] == color |
| 1973 | && !is_self_atari(NORTH(libs[l1]), color)) |
| 1974 | ADD_CANDIDATE_MOVE(NORTH(libs[l1]), 0, *moves, "bamboo_rescue"); |
| 1975 | } |
| 1976 | else if (libs[l1] == NORTH(libs[l2]) || libs[l1] == SOUTH(libs[l2])) { |
| 1977 | if (board[WEST(libs[l1])] == EMPTY |
| 1978 | && board[WEST(libs[l2])] == color |
| 1979 | && !is_self_atari(WEST(libs[l1]), color)) |
| 1980 | ADD_CANDIDATE_MOVE(WEST(libs[l1]), 0, *moves, "bamboo_rescue"); |
| 1981 | if (board[EAST(libs[l1])] == EMPTY |
| 1982 | && board[EAST(libs[l2])] == color |
| 1983 | && !is_self_atari(EAST(libs[l1]), color)) |
| 1984 | ADD_CANDIDATE_MOVE(EAST(libs[l1]), 0, *moves, "bamboo_rescue"); |
| 1985 | } |
| 1986 | } |
| 1987 | } |
| 1988 | |
| 1989 | |
| 1990 | /* In a situation like this: |
| 1991 | * |
| 1992 | * OOXXXX the following code can find the |
| 1993 | * .OXOOX defensive move at 'c'. |
| 1994 | * .cO.OX |
| 1995 | * .X.OOX |
| 1996 | * ------ |
| 1997 | * |
| 1998 | * OOXXXX It also can find more general moves like 'c' here. |
| 1999 | * .OXOOX |
| 2000 | * cXO.OX |
| 2001 | * ...OOX |
| 2002 | * ------ |
| 2003 | */ |
| 2004 | static void |
| 2005 | special_rescue2_moves(int str, int libs[2], struct reading_moves *moves) |
| 2006 | { |
| 2007 | int color = board[str]; |
| 2008 | int other = OTHER_COLOR(color); |
| 2009 | int newlibs[4]; |
| 2010 | int liberties; |
| 2011 | int newstr; |
| 2012 | int k, r, s; |
| 2013 | |
| 2014 | for (r = 0; r < 2; r++) { |
| 2015 | /* Let alib be one of the liberties and require it to be suicide |
| 2016 | * for the opponent. |
| 2017 | */ |
| 2018 | int alib = libs[r]; |
| 2019 | if (!is_suicide(alib, other)) |
| 2020 | continue; |
| 2021 | |
| 2022 | for (k = 0; k < 4; k++) { |
| 2023 | if (board[alib + delta[k]] == color |
| 2024 | && !same_string(alib + delta[k], str)) { |
| 2025 | newstr = alib + delta[k]; |
| 2026 | liberties = findlib(newstr, 4, newlibs); |
| 2027 | |
| 2028 | for (s = 0; s < liberties && s < 4; s++) { |
| 2029 | if (!is_self_atari(newlibs[s], color)) |
| 2030 | ADD_CANDIDATE_MOVE(newlibs[s], 0, *moves, "special_rescue2"); |
| 2031 | } |
| 2032 | break_chain_moves(newstr, moves); |
| 2033 | break_chain2_efficient_moves(newstr, moves); |
| 2034 | edge_clamp_moves(newstr, moves); |
| 2035 | } |
| 2036 | } |
| 2037 | } |
| 2038 | } |
| 2039 | |
| 2040 | |
| 2041 | /* In a situation like this: |
| 2042 | * |
| 2043 | * ...X.XXO |
| 2044 | * .XXXOOXO |
| 2045 | * XXOO.OXO the following code can find the |
| 2046 | * .O..X.*. defensive move at '*'. |
| 2047 | * -------- |
| 2048 | * |
| 2049 | * OXO cde |
| 2050 | * .*. afg |
| 2051 | * --- b-- |
| 2052 | */ |
| 2053 | static void |
| 2054 | special_rescue3_moves(int str, int libs[3], struct reading_moves *moves) |
| 2055 | { |
| 2056 | int color = board[str]; |
| 2057 | int other = OTHER_COLOR(color); |
| 2058 | int apos, bpos, cpos, dpos, epos, fpos, gpos; |
| 2059 | int k, l, r; |
| 2060 | |
| 2061 | ASSERT1(countlib(str) == 3, str); |
| 2062 | |
| 2063 | for (r = 0; r < 3; r++) { |
| 2064 | /* Let (apos) be one of the three liberties. */ |
| 2065 | apos = libs[r]; |
| 2066 | /* Try to find the configuration above. */ |
| 2067 | for (k = 0; k < 4; k++) { |
| 2068 | bpos = apos + delta[k]; |
| 2069 | if (ON_BOARD(bpos)) |
| 2070 | continue; |
| 2071 | |
| 2072 | cpos = apos - delta[k]; |
| 2073 | if (board[cpos] != color) |
| 2074 | continue; |
| 2075 | |
| 2076 | if (!same_string(cpos, str)) |
| 2077 | continue; |
| 2078 | |
| 2079 | for (l = 0; l < 2; l++) { |
| 2080 | int normal = delta[(k+1)%4]; |
| 2081 | if (l == 1) |
| 2082 | normal = -normal; |
| 2083 | |
| 2084 | dpos = cpos + normal; |
| 2085 | if (board[dpos] != other) |
| 2086 | continue; |
| 2087 | |
| 2088 | epos = dpos + normal; |
| 2089 | if (board[epos] != color) |
| 2090 | continue; |
| 2091 | |
| 2092 | fpos = apos + normal; |
| 2093 | if (board[fpos] != EMPTY) |
| 2094 | continue; |
| 2095 | |
| 2096 | gpos = fpos + normal; |
| 2097 | if (board[gpos] != EMPTY) |
| 2098 | continue; |
| 2099 | |
| 2100 | /* Configuration found. Now require an X move at 'a' not |
| 2101 | * getting too many liberties. |
| 2102 | */ |
| 2103 | |
| 2104 | if (approxlib(apos, other, 4, NULL) > 3) |
| 2105 | continue; |
| 2106 | |
| 2107 | /* Try to play at (fpos). */ |
| 2108 | ADD_CANDIDATE_MOVE(fpos, 0, *moves, "special_rescue3"); |
| 2109 | } |
| 2110 | } |
| 2111 | } |
| 2112 | } |
| 2113 | |
| 2114 | |
| 2115 | /* This code can find moves to counter attack moves generated by |
| 2116 | * special_attack3_moves(). In case such an attack move has only two |
| 2117 | * liberties, this function finds the liberty which is not common with |
| 2118 | * the attacked string. |
| 2119 | * |
| 2120 | * For a typical example, see reading:198 where black L7 is generated |
| 2121 | * by special_attack3_moves() and the response at L8 is generated by |
| 2122 | * this function. |
| 2123 | */ |
| 2124 | |
| 2125 | static void |
| 2126 | special_rescue4_moves(int str, int libs[2], struct reading_moves *moves) |
| 2127 | { |
| 2128 | int color = board[str]; |
| 2129 | int other = OTHER_COLOR(color); |
| 2130 | int xpos; |
| 2131 | int apos; |
| 2132 | int bpos; |
| 2133 | int libs2[2]; |
| 2134 | int k; |
| 2135 | int r; |
| 2136 | |
| 2137 | ASSERT1(countlib(str) == 2, str); |
| 2138 | |
| 2139 | for (k = 0; k < 2; k++) { |
| 2140 | apos = libs[k]; |
| 2141 | bpos = libs[1-k]; |
| 2142 | |
| 2143 | if (apos == SOUTH(bpos) || apos == NORTH(bpos)) { |
| 2144 | if (board[WEST(apos)] == other) |
| 2145 | xpos = WEST(apos); |
| 2146 | else if (board[EAST(apos)] == other) |
| 2147 | xpos = EAST(apos); |
| 2148 | else |
| 2149 | continue; |
| 2150 | } |
| 2151 | else if (apos == WEST(bpos) || apos == EAST(bpos)) { |
| 2152 | if (board[SOUTH(apos)] == other) |
| 2153 | xpos = SOUTH(apos); |
| 2154 | else if (board[NORTH(apos)] == other) |
| 2155 | xpos = NORTH(apos); |
| 2156 | else |
| 2157 | continue; |
| 2158 | } |
| 2159 | else |
| 2160 | return; /* Incorrect configuration, give up. */ |
| 2161 | |
| 2162 | if (findlib(xpos, 2, libs2) == 2) { |
| 2163 | for (r = 0; r < 2; r++) |
| 2164 | if (libs2[r] != apos && libs2[r] != bpos |
| 2165 | && !is_self_atari(libs2[r], color)) |
| 2166 | ADD_CANDIDATE_MOVE(libs2[r], 0, *moves, "special_rescue4"); |
| 2167 | } |
| 2168 | } |
| 2169 | } |
| 2170 | |
| 2171 | /* In a situation like this: |
| 2172 | * |
| 2173 | * .XXXXX |
| 2174 | * XX.*OO |
| 2175 | * X.OX.. the following code can find the |
| 2176 | * ...... defensive move at '*'. |
| 2177 | * ------ |
| 2178 | * |
| 2179 | * .* ac |
| 2180 | * OX bd |
| 2181 | * |
| 2182 | * The only requirement is that d has at most as many liberties as b, |
| 2183 | * and as the newly placed stone at c. |
| 2184 | */ |
| 2185 | static void |
| 2186 | hane_rescue_moves(int str, int libs[4], struct reading_moves *moves) |
| 2187 | { |
| 2188 | int color = board[str]; |
| 2189 | int other = OTHER_COLOR(color); |
| 2190 | int apos, bpos, cpos, dpos; |
| 2191 | int num_libs = countlib(str); |
| 2192 | int k, l, r; |
| 2193 | |
| 2194 | ASSERT1(num_libs <= 4, str); |
| 2195 | |
| 2196 | for (r = 0; r < num_libs; r++) { |
| 2197 | /* Let (apos) be one of the three liberties. */ |
| 2198 | apos = libs[r]; |
| 2199 | /* Try to find the configuration above. */ |
| 2200 | for (k = 0; k < 4; k++) { |
| 2201 | bpos = apos + delta[k]; |
| 2202 | if (board[bpos] != color) |
| 2203 | continue; |
| 2204 | |
| 2205 | if (!same_string(bpos, str)) |
| 2206 | continue; |
| 2207 | |
| 2208 | for (l = 0; l < 2; l++) { |
| 2209 | int normal = delta[(k+1)%4]; |
| 2210 | if (l == 1) |
| 2211 | normal = -normal; |
| 2212 | |
| 2213 | cpos = apos + normal; |
| 2214 | if (board[cpos] != EMPTY) |
| 2215 | continue; |
| 2216 | |
| 2217 | dpos = bpos + normal; |
| 2218 | if (board[dpos] != other) |
| 2219 | continue; |
| 2220 | |
| 2221 | /* Configuration found. Now check liberty constraint. */ |
| 2222 | { |
| 2223 | int dlibs = countlib(dpos); |
| 2224 | if (dlibs > num_libs |
| 2225 | || dlibs > accuratelib(cpos, color, dlibs, NULL)) |
| 2226 | continue; |
| 2227 | } |
| 2228 | |
| 2229 | if (0 && !in_list(cpos, moves->num, moves->pos)) { |
| 2230 | gprintf("hane_rescue_move added for %1m at %1m\n", str, cpos); |
| 2231 | dump_stack(); |
| 2232 | showboard(0); |
| 2233 | } |
| 2234 | ADD_CANDIDATE_MOVE(cpos, 0, *moves, "hane_rescue"); |
| 2235 | } |
| 2236 | } |
| 2237 | } |
| 2238 | } |
| 2239 | |
| 2240 | |
| 2241 | /* In situations like these |
| 2242 | * |
| 2243 | * |XXXX |.X... |.X... |
| 2244 | * |OOOX |.XOO. |XXOO. |
| 2245 | * |..OX |OOXO. |OOXO. |
| 2246 | * |O.OX |O.X*O |O.XOO |
| 2247 | * |.X*. |O.X.O |O.X*O |
| 2248 | * +---- +----- +----- |
| 2249 | * |
| 2250 | * the smaller of the O strings can be defended by *. The property |
| 2251 | * they have in common is that the defended string has (at least) two |
| 2252 | * liberties in common with an X string and it's effective to play on |
| 2253 | * an exterior liberty of this string. Similarly it may be worth |
| 2254 | * defending a weak neighbor of the X string. |
| 2255 | * |
| 2256 | * This function may be called for strings with 2 or 3 liberties and |
| 2257 | * returns moves which are potentially useful in these positions. |
| 2258 | */ |
| 2259 | static void |
| 2260 | special_rescue5_moves(int str, int libs[3], |
| 2261 | struct reading_moves *moves) |
| 2262 | { |
| 2263 | int color = board[str]; |
| 2264 | int other = OTHER_COLOR(color); |
| 2265 | int apos, bpos; |
| 2266 | int k, r, s; |
| 2267 | int liberties = countlib(str); |
| 2268 | int libs2[4]; |
| 2269 | int liberties2; |
| 2270 | |
| 2271 | ASSERT1(liberties == 2 || liberties == 3, str); |
| 2272 | |
| 2273 | for (r = 0; r < liberties; r++) { |
| 2274 | apos = libs[r]; |
| 2275 | |
| 2276 | for (k = 0; k < 4; k++) { |
| 2277 | bpos = apos + delta[k]; |
| 2278 | if (board[bpos] != other) |
| 2279 | continue; |
| 2280 | |
| 2281 | /* Don't bother if it has too many liberties. */ |
| 2282 | if (countlib(bpos) > liberties + 1) |
| 2283 | continue; |
| 2284 | |
| 2285 | if (count_common_libs(str, bpos) < 2) |
| 2286 | continue; |
| 2287 | |
| 2288 | liberties2 = findlib(bpos, 4, libs2); |
| 2289 | for (s = 0; s < liberties2; s++) |
| 2290 | if (!liberty_of_string(libs2[s], str) |
| 2291 | && !is_self_atari(libs2[s], color)) |
| 2292 | ADD_CANDIDATE_MOVE(libs2[s], 0, *moves, "special_rescue5-A"); |
| 2293 | |
| 2294 | /* Reinforce the second order chain. */ |
| 2295 | if (liberties2 <= liberties) { |
| 2296 | int adj; |
| 2297 | int adjs[MAXCHAIN]; |
| 2298 | int t; |
| 2299 | adj = chainlinks2(bpos, adjs, 1); |
| 2300 | for (t = 0; t < adj; t++) { |
| 2301 | int cpos; |
| 2302 | break_chain_moves(adjs[t], moves); |
| 2303 | |
| 2304 | findlib(adjs[t], 1, &cpos); |
| 2305 | if (!is_self_atari(cpos, color)) |
| 2306 | ADD_CANDIDATE_MOVE(cpos, 0, *moves, "special_rescue5-B"); |
| 2307 | } |
| 2308 | |
| 2309 | /* Defend against double atari in the surrounding chain early. */ |
| 2310 | double_atari_chain2_moves(bpos, moves, 0); |
| 2311 | } |
| 2312 | } |
| 2313 | } |
| 2314 | } |
| 2315 | |
| 2316 | |
| 2317 | /* In situations like this |
| 2318 | * |
| 2319 | * |.bOX |
| 2320 | * |.Xa. |
| 2321 | * |.OXX |
| 2322 | * |.O.. |
| 2323 | * |.XX. |
| 2324 | * |
| 2325 | * the lower O string can often be defended at a or b. |
| 2326 | * |
| 2327 | * This function may be called for strings with 3 or 4 liberties and |
| 2328 | * returns the * moves in the configuration below: |
| 2329 | * |
| 2330 | * |..O |.*O |
| 2331 | * |.X. |.c* |
| 2332 | * |.O? |ab? |
| 2333 | * |
| 2334 | * It also adds the * move in these configurations: |
| 2335 | * |
| 2336 | * |.X. |.c* |
| 2337 | * |.OX |abX |
| 2338 | * |
| 2339 | * |.X. |.c* |
| 2340 | * |.O. |ab. |
| 2341 | * |
| 2342 | * Provided that * is not a self atari and that the X strings have |
| 2343 | * sufficiently few liberties. |
| 2344 | */ |
| 2345 | static void |
| 2346 | special_rescue6_moves(int str, int libs[3], struct reading_moves *moves) |
| 2347 | { |
| 2348 | int color = board[str]; |
| 2349 | int other = OTHER_COLOR(color); |
| 2350 | int apos, bpos, cpos; |
| 2351 | int right, up; |
| 2352 | int k, l, r; |
| 2353 | int liberties = countlib(str); |
| 2354 | |
| 2355 | ASSERT1(liberties == 3 || liberties == 4, str); |
| 2356 | |
| 2357 | for (r = 0; r < liberties; r++) { |
| 2358 | apos = libs[r]; |
| 2359 | |
| 2360 | for (k = 0; k < 4; k++) { |
| 2361 | right = delta[k]; |
| 2362 | |
| 2363 | if (ON_BOARD(apos - right)) |
| 2364 | continue; |
| 2365 | |
| 2366 | bpos = apos + right; |
| 2367 | if (board[bpos] != color || !same_string(str, bpos)) |
| 2368 | continue; |
| 2369 | |
| 2370 | for (l = 0; l < 2; l++) { |
| 2371 | up = delta[(k+1) % 4]; |
| 2372 | if (l == 1) |
| 2373 | up = -up; |
| 2374 | |
| 2375 | cpos = bpos + up; |
| 2376 | if (board[cpos] != other) |
| 2377 | continue; |
| 2378 | |
| 2379 | if (board[apos + up] != EMPTY) |
| 2380 | continue; |
| 2381 | |
| 2382 | if (board[cpos + right] != EMPTY) |
| 2383 | continue; |
| 2384 | |
| 2385 | if (board[apos + up + up] == EMPTY |
| 2386 | && board[cpos + up] == EMPTY |
| 2387 | && board[cpos + up + right] == color) { |
| 2388 | ADD_CANDIDATE_MOVE(cpos + right, 0, *moves, "special_rescue6-A"); |
| 2389 | ADD_CANDIDATE_MOVE(cpos + up, 0, *moves, "special_rescue6-B"); |
| 2390 | } |
| 2391 | else if (countlib(cpos) <= 3 |
| 2392 | && (board[bpos + right] == EMPTY |
| 2393 | || (board[bpos + right] == other |
| 2394 | && countlib(bpos + right) <= 4)) |
| 2395 | && !is_self_atari(cpos + right, color)) { |
| 2396 | ADD_CANDIDATE_MOVE(cpos + right, 0, *moves, "special_rescue6-C"); |
| 2397 | } |
| 2398 | } |
| 2399 | } |
| 2400 | } |
| 2401 | } |
| 2402 | |
| 2403 | /* |
| 2404 | * set_up_snapback_moves() is called with (str) a string having a |
| 2405 | * single liberty at (lib). |
| 2406 | * |
| 2407 | * This adds moves which may defend a string in atari by capturing a |
| 2408 | * neighbor in a snapback. One example is this position: |
| 2409 | * |
| 2410 | * OOOOO |
| 2411 | * OXXXO |
| 2412 | * OX.OX |
| 2413 | * OXOXX |
| 2414 | * OX*.. |
| 2415 | * ----- |
| 2416 | * |
| 2417 | * This code also finds the move * to defend the lone O stone with ko |
| 2418 | * in this position: |
| 2419 | * |
| 2420 | * |XXXXX |
| 2421 | * |XOOOX |
| 2422 | * |OX.OO |
| 2423 | * |.*... |
| 2424 | * +----- |
| 2425 | * |
| 2426 | */ |
| 2427 | |
| 2428 | static void |
| 2429 | set_up_snapback_moves(int str, int lib, struct reading_moves *moves) |
| 2430 | { |
| 2431 | int color = board[str]; |
| 2432 | int other = OTHER_COLOR(color); |
| 2433 | int libs2[2]; |
| 2434 | |
| 2435 | ASSERT1(countlib(str) == 1, str); |
| 2436 | |
| 2437 | /* This can only work if our string is a single stone and the |
| 2438 | * opponent is short of liberties. |
| 2439 | */ |
| 2440 | if (stackp <= backfill_depth |
| 2441 | && countstones(str) == 1 |
| 2442 | && approxlib(lib, other, 2, libs2) == 1 |
| 2443 | && (!is_self_atari(libs2[0], color) |
| 2444 | || is_ko(libs2[0], color, NULL))) |
| 2445 | ADD_CANDIDATE_MOVE(libs2[0], 0, *moves, "set_up_snapback"); |
| 2446 | } |
| 2447 | |
| 2448 | |
| 2449 | |
| 2450 | /* This function adds liberties of the superstring as candidate moves. |
| 2451 | * For performance, this is restricted to strings with liberty_cap |
| 2452 | * liberties, and to cases where at most 5 liberties would get considered. |
| 2453 | * |
| 2454 | * When attacking, we also try backfilling in case the direct approach |
| 2455 | * would be self-atari. |
| 2456 | * When defending, we also try second order liberties. |
| 2457 | */ |
| 2458 | static void |
| 2459 | superstring_moves(int str, struct reading_moves *moves, |
| 2460 | int liberty_cap, int does_attack) |
| 2461 | { |
| 2462 | int ss_liberties; |
| 2463 | int ss_libs[MAX_LIBERTIES + 4]; |
| 2464 | int color = board[str]; |
| 2465 | int other = OTHER_COLOR(color); |
| 2466 | int k; |
| 2467 | |
| 2468 | find_superstring_liberties(str, &ss_liberties, ss_libs, liberty_cap); |
| 2469 | if (ss_liberties <= 5) { |
| 2470 | for (k = 0; k < ss_liberties; k++) { |
| 2471 | int apos = ss_libs[k]; |
| 2472 | int alibs[2]; |
| 2473 | int alib = accuratelib(apos, other, 2, alibs); |
| 2474 | |
| 2475 | if (liberty_of_string(apos, str)) |
| 2476 | continue; |
| 2477 | |
| 2478 | if (alib >= 2) |
| 2479 | ADD_CANDIDATE_MOVE(apos, 0, *moves, "superstring liberty"); |
| 2480 | else if (alib == 1 |
| 2481 | && does_attack |
| 2482 | && board[alibs[0]] == EMPTY |
| 2483 | && approxlib(alibs[0], other, 3, NULL) >= 3) |
| 2484 | ADD_CANDIDATE_MOVE(alibs[0], 0, *moves, "superstring backfill"); |
| 2485 | |
| 2486 | if (!does_attack) |
| 2487 | special_rescue_moves(str, apos, moves); |
| 2488 | } |
| 2489 | } |
| 2490 | } |
| 2491 | |
| 2492 | |
| 2493 | /* This function is somewhat related to superstring_moves() but tries |
| 2494 | * to find moves to squeeze out liberties from the superstring, aiming |
| 2495 | * to capture the main string in a shortage of liberties. |
| 2496 | * |
| 2497 | * For a typical example, see the move E9 in reading:203,204. It is |
| 2498 | * assumed that the same move is effective both for attack and |
| 2499 | * defense. |
| 2500 | */ |
| 2501 | static void |
| 2502 | squeeze_moves(int str, struct reading_moves *moves) |
| 2503 | { |
| 2504 | int color = board[str]; |
| 2505 | int other = OTHER_COLOR(color); |
| 2506 | int libs[4]; |
| 2507 | int num_libs; |
| 2508 | int libs2[4]; |
| 2509 | int num_libs2; |
| 2510 | int k; |
| 2511 | int r; |
| 2512 | int potential_move = NO_MOVE; |
| 2513 | int previous_liberty; |
| 2514 | |
| 2515 | num_libs = findlib(str, 4, libs); |
| 2516 | gg_assert(num_libs <= 4); |
| 2517 | |
| 2518 | for (k = 0; k < num_libs; k++) { |
| 2519 | if (!is_suicide(libs[k], other)) |
| 2520 | continue; |
| 2521 | |
| 2522 | num_libs2 = approxlib(libs[k], color, 4, libs2); |
| 2523 | if (num_libs2 != num_libs) |
| 2524 | continue; |
| 2525 | |
| 2526 | for (r = 0; r < num_libs2; r++) |
| 2527 | if (!liberty_of_string(libs2[r], str)) { |
| 2528 | potential_move = libs2[r]; |
| 2529 | break; |
| 2530 | } |
| 2531 | |
| 2532 | previous_liberty = libs[k]; |
| 2533 | |
| 2534 | while (is_suicide(potential_move, other)) { |
| 2535 | num_libs2 = approxlib(potential_move, color, 3, libs2); |
| 2536 | if (num_libs2 != 2) { |
| 2537 | potential_move = NO_MOVE; |
| 2538 | break; |
| 2539 | } |
| 2540 | if (libs2[0] == previous_liberty) { |
| 2541 | previous_liberty = potential_move; |
| 2542 | potential_move = libs2[1]; |
| 2543 | } |
| 2544 | else { |
| 2545 | previous_liberty = potential_move; |
| 2546 | potential_move = libs2[0]; |
| 2547 | } |
| 2548 | if (liberty_of_string(potential_move, str)) { |
| 2549 | potential_move = NO_MOVE; |
| 2550 | break; |
| 2551 | } |
| 2552 | } |
| 2553 | |
| 2554 | if (potential_move == NO_MOVE |
| 2555 | || !is_self_atari(potential_move, other)) |
| 2556 | continue; |
| 2557 | |
| 2558 | approxlib(potential_move, other, 1, libs2); |
| 2559 | |
| 2560 | num_libs2 = approxlib(libs2[0], color, MAXLIBS, NULL); |
| 2561 | |
| 2562 | if (num_libs2 < 3 |
| 2563 | && num_libs2 < approxlib(potential_move, color, MAXLIBS, NULL)) |
| 2564 | ADD_CANDIDATE_MOVE(potential_move, 0, *moves, "squeeze move"); |
| 2565 | } |
| 2566 | } |
| 2567 | |
| 2568 | |
| 2569 | /* In positions like |
| 2570 | * |
| 2571 | * |.XXOO. |
| 2572 | * |XXOX.. |
| 2573 | * |OOOX*. |
| 2574 | * |...... |
| 2575 | * +------ |
| 2576 | * |
| 2577 | * the O stones to the left are best defended by the move at *. |
| 2578 | * |
| 2579 | * This function tries to find an adjacent string (apos) with exactly |
| 2580 | * three liberties. One of the liberties (bpos) must be on the edge |
| 2581 | * (but not in the corner). Diagonal to this liberty must be one stone |
| 2582 | * of the attacked string (cpos) and another liberty (dpos) of the |
| 2583 | * adjacent string. The third liberty (epos) must be adjacent to |
| 2584 | * (dpos). Furthermore must an O stone at (dpos) get at least three |
| 2585 | * liberties and and X stone at (epos) must get at most three |
| 2586 | * liberties. |
| 2587 | * |
| 2588 | * |.XXOO. |
| 2589 | * |XXOXe. |
| 2590 | * |OOcad. |
| 2591 | * |...b.. |
| 2592 | * +------ |
| 2593 | * |
| 2594 | * The defense move at (dpos) is proposed if the above conditions |
| 2595 | * are satisfied. |
| 2596 | */ |
| 2597 | |
| 2598 | static void |
| 2599 | edge_clamp_moves(int str, struct reading_moves *moves) |
| 2600 | { |
| 2601 | int color = board[str]; |
| 2602 | int other = OTHER_COLOR(color); |
| 2603 | int apos; |
| 2604 | int bpos; |
| 2605 | int cpos; |
| 2606 | int dpos; |
| 2607 | int epos; |
| 2608 | int adj, adjs[MAXCHAIN]; |
| 2609 | int libs[3]; |
| 2610 | int k, l, r; |
| 2611 | |
| 2612 | /* Pick up neighbors with three liberties. */ |
| 2613 | adj = chainlinks2(str, adjs, 3); |
| 2614 | |
| 2615 | for (r = 0; r < adj; r++) { |
| 2616 | apos = adjs[r]; |
| 2617 | /* Find a liberty at the edge. */ |
| 2618 | bpos = NO_MOVE; |
| 2619 | findlib(apos, 3, libs); |
| 2620 | for (k = 0; k < 3; k++) { |
| 2621 | if (is_edge_vertex(libs[k])) { |
| 2622 | bpos = libs[k]; |
| 2623 | break; |
| 2624 | } |
| 2625 | } |
| 2626 | if (bpos == NO_MOVE) |
| 2627 | continue; |
| 2628 | |
| 2629 | /* Edge liberty found. Establish up and right directions. */ |
| 2630 | for (k = 0; k < 4; k++) { |
| 2631 | int up = delta[k]; |
| 2632 | if (ON_BOARD(bpos - up)) |
| 2633 | continue; |
| 2634 | if (board[bpos + up] != other) |
| 2635 | continue; |
| 2636 | |
| 2637 | for (l = 0; l < 2; l++) { |
| 2638 | int right = delta[(k+1)%4]; |
| 2639 | if (l == 1) |
| 2640 | right = -right; |
| 2641 | |
| 2642 | cpos = bpos + up - right; |
| 2643 | dpos = bpos + up + right; |
| 2644 | |
| 2645 | if (board[cpos] != color || !same_string(cpos, str)) |
| 2646 | continue; |
| 2647 | |
| 2648 | if (board[dpos] != EMPTY || !liberty_of_string(dpos, apos)) |
| 2649 | continue; |
| 2650 | |
| 2651 | epos = dpos + up; |
| 2652 | |
| 2653 | if (board[epos] != EMPTY || !liberty_of_string(epos, apos)) |
| 2654 | continue; |
| 2655 | |
| 2656 | if (approxlib(dpos, color, 3, NULL) < 3) |
| 2657 | continue; |
| 2658 | |
| 2659 | if (approxlib(epos, other, 4, NULL) > 3) |
| 2660 | continue; |
| 2661 | |
| 2662 | /* (dpos) looks like a good move. Add it to the list with a |
| 2663 | * substantial initial score. |
| 2664 | */ |
| 2665 | ADD_CANDIDATE_MOVE(dpos, 10, *moves, "edge_clamp"); |
| 2666 | } |
| 2667 | } |
| 2668 | } |
| 2669 | } |
| 2670 | |
| 2671 | |
| 2672 | /* |
| 2673 | * This function handles some special cases on the edge. |
| 2674 | * |
| 2675 | * 1. If (str) points to a string and 'a' an edge liberty of it, |
| 2676 | * there is no point of trying to defend the string by crawling |
| 2677 | * along the edge if there is no hope of ever getting more liberties. |
| 2678 | * This is of course if the blocking enemy group has enough liberties |
| 2679 | * of its own. |
| 2680 | * |
| 2681 | * XX XX |
| 2682 | * O. Oa |
| 2683 | * -- -- |
| 2684 | * |
| 2685 | * This function searches the edge towards the corner and sees if there |
| 2686 | * is a friendly stone on one of the two first lines. If not, the move |
| 2687 | * is removed from the list of moves. |
| 2688 | * |
| 2689 | * 2. If (str) points to a string and 'a' an edge liberty of it, |
| 2690 | * the drawing back/climbing up move 'b' is often correct attack or |
| 2691 | * defense. Another good move to try is 'c' (but usually not for |
| 2692 | * defense of a 2 liberty string). |
| 2693 | * |
| 2694 | * X.? Xbc |
| 2695 | * O.. Oa. |
| 2696 | * --- --- |
| 2697 | * |
| 2698 | * This function adds the points configured like 'b' and 'c' relative to |
| 2699 | * (str) to the list of moves. |
| 2700 | * |
| 2701 | * color is the color to move. |
| 2702 | */ |
| 2703 | |
| 2704 | static void |
| 2705 | propose_edge_moves(int str, int *libs, int liberties, |
| 2706 | struct reading_moves *moves, int to_move) |
| 2707 | { |
| 2708 | int color = board[str]; |
| 2709 | int other = OTHER_COLOR(color); |
| 2710 | int right; |
| 2711 | int up; |
| 2712 | int apos; |
| 2713 | int k, l; |
| 2714 | int r; |
| 2715 | |
| 2716 | for (r = 0; r < liberties; r++) { |
| 2717 | apos = libs[r]; |
| 2718 | for (k = 0; k < 4; k++) { |
| 2719 | up = delta[k]; |
| 2720 | if (ON_BOARD(apos - up)) |
| 2721 | continue; |
| 2722 | |
| 2723 | for (l = 0; l < 2; l++) { |
| 2724 | right = delta[(k+1)%4]; |
| 2725 | if (l == 1) |
| 2726 | right = -right; |
| 2727 | |
| 2728 | if (board[apos + up] == other /* other on top of liberty */ |
| 2729 | && countlib(apos + up) > 4 /* blocking group must be secure */ |
| 2730 | && color == to_move) { /* only applicable as defense */ |
| 2731 | |
| 2732 | /* Case 1: other above the liberty (crawl along the edge). */ |
| 2733 | int xpos = apos; |
| 2734 | |
| 2735 | while (ON_BOARD(xpos)) { |
| 2736 | if (board[xpos] == color |
| 2737 | || board[xpos + up] == color) |
| 2738 | break; |
| 2739 | |
| 2740 | xpos += right; |
| 2741 | } |
| 2742 | |
| 2743 | /* If no friendly stone found, then it is pointless and we |
| 2744 | * can just as well remove the move. |
| 2745 | */ |
| 2746 | if (!ON_BOARD(xpos)) { |
| 2747 | REMOVE_CANDIDATE_MOVE(apos, *moves); |
| 2748 | } |
| 2749 | } |
| 2750 | else if (board[apos + up] == EMPTY /* empty above the liberty */ |
| 2751 | && board[apos - right + up] == other |
| 2752 | && board[apos + right] == EMPTY) { /* empty to the right */ |
| 2753 | |
| 2754 | /* Case 2: Try to escape or contain. */ |
| 2755 | |
| 2756 | /* Add b |
| 2757 | * If adjacent X stone in atari, boost the initial score of this |
| 2758 | * move. |
| 2759 | */ |
| 2760 | if (countlib(apos + up - right) == 1) |
| 2761 | ADD_CANDIDATE_MOVE(apos + up, 10, *moves, "propose_edge-A"); |
| 2762 | else { |
| 2763 | ADD_CANDIDATE_MOVE(apos + up, 0, *moves, "propose_edge-B"); |
| 2764 | |
| 2765 | /* Add c if empty */ |
| 2766 | if (board[apos + right + up] == EMPTY |
| 2767 | && (liberties != 2 || color != to_move)) |
| 2768 | ADD_CANDIDATE_MOVE(apos + right + up, 0, *moves, |
| 2769 | "propose_edge-C"); |
| 2770 | } |
| 2771 | } |
| 2772 | } |
| 2773 | } |
| 2774 | } |
| 2775 | } |
| 2776 | |
| 2777 | |
| 2778 | /* ================================================================ */ |
| 2779 | /* Attacking functions */ |
| 2780 | /* ================================================================ */ |
| 2781 | |
| 2782 | |
| 2783 | /* Like attack. If the opponent is komaster reading functions will not try |
| 2784 | * to take ko. |
| 2785 | */ |
| 2786 | static int |
| 2787 | do_attack(int str, int *move) |
| 2788 | { |
| 2789 | int color = board[str]; |
| 2790 | int xpos = NO_MOVE; |
| 2791 | int liberties; |
| 2792 | int result = 0; |
| 2793 | int retval; |
| 2794 | |
| 2795 | SETUP_TRACE_INFO("attack", str); |
| 2796 | |
| 2797 | ASSERT1(color != 0, str); |
| 2798 | |
| 2799 | if (color == 0) /* if assertions are turned off, silently fails */ |
| 2800 | return 0; |
| 2801 | |
| 2802 | str = find_origin(str); |
| 2803 | liberties = countlib(str); |
| 2804 | |
| 2805 | if (liberties > 4 |
| 2806 | || (liberties == 4 && stackp > fourlib_depth) |
| 2807 | || (liberties == 3 && stackp > depth)) { |
| 2808 | /* No need to cache the result in these cases. */ |
| 2809 | if (sgf_dumptree) { |
| 2810 | char buf[100]; |
| 2811 | sprintf(buf, "got 4 liberties (stackp:%d>%d)", |
| 2812 | stackp, fourlib_depth); |
| 2813 | SGFTRACE(0, 0, buf); |
| 2814 | } |
| 2815 | return 0; |
| 2816 | } |
| 2817 | |
| 2818 | /* Set "killer move" up. This move (if set) was successful in |
| 2819 | * another variation, so it is reasonable to try it now. However, |
| 2820 | * we only do this if the string has 4 liberties - otherwise the |
| 2821 | * situation changes too much from variation to variation. |
| 2822 | */ |
| 2823 | if (liberties > 3 && move) |
| 2824 | xpos = *move; |
| 2825 | |
| 2826 | /* Note that if return value is 1 (too small depth), the move will |
| 2827 | * still be used for move ordering. |
| 2828 | */ |
| 2829 | if (stackp <= depth |
| 2830 | && tt_get(&ttable, ATTACK, str, NO_MOVE, depth - stackp, NULL, |
| 2831 | &retval, NULL, &xpos) == 2) { |
| 2832 | TRACE_CACHED_RESULT(retval, xpos); |
| 2833 | SGFTRACE(xpos, retval, "cached"); |
| 2834 | if (move) |
| 2835 | *move = xpos; |
| 2836 | return retval; |
| 2837 | } |
| 2838 | |
| 2839 | /* Treat the attack differently depending on how many liberties the |
| 2840 | string at (str) has. */ |
| 2841 | if (liberties == 1) |
| 2842 | result = attack1(str, &xpos); |
| 2843 | else if (liberties == 2) { |
| 2844 | if (stackp > depth + 10) |
| 2845 | result = simple_ladder(str, &xpos); |
| 2846 | else |
| 2847 | result = attack2(str, &xpos); |
| 2848 | } |
| 2849 | else if (liberties == 3) |
| 2850 | result = attack3(str, &xpos); |
| 2851 | else if (liberties == 4) |
| 2852 | result = attack4(str, &xpos); |
| 2853 | |
| 2854 | |
| 2855 | ASSERT1(result >= 0 && result <= WIN, str); |
| 2856 | |
| 2857 | if (result) { |
| 2858 | READ_RETURN(ATTACK, str, depth - stackp, move, xpos, result); |
| 2859 | } |
| 2860 | |
| 2861 | READ_RETURN0(ATTACK, str, depth - stackp); |
| 2862 | } |
| 2863 | |
| 2864 | |
| 2865 | /* If (str) points to a group with exactly one liberty, attack1 |
| 2866 | * determines whether it can be captured by playing at this liberty. |
| 2867 | * If successful, (*move) is the killing move. move may be NULL if |
| 2868 | * caller is only interested in whether it can be captured. |
| 2869 | * |
| 2870 | * The attack may fail for two different reasons. The first one is |
| 2871 | * that the attack may be an illegal ko capture, in this case KO_B is |
| 2872 | * returned (need to play a ko threat before the attack can be |
| 2873 | * fulfilled). |
| 2874 | * |
| 2875 | * The second cause for failure is that the attack is caught in a |
| 2876 | * snapback. We must require that it is a proper snapback, though. By |
| 2877 | * proper snapback we mean a position like |
| 2878 | * |
| 2879 | * XXXXO |
| 2880 | * XO.XO |
| 2881 | * XOXOO |
| 2882 | * ----- |
| 2883 | * |
| 2884 | * where capture by O and recapture by X leaves the X stone intact |
| 2885 | * with at least two liberties: |
| 2886 | * |
| 2887 | * XXXXO |
| 2888 | * X..XO |
| 2889 | * X.XOO |
| 2890 | * ----- |
| 2891 | * |
| 2892 | * There are a number of different kinds of improper snapbacks, which |
| 2893 | * have in common that the attacked string ends up captured. We don't |
| 2894 | * consider these as failures to attack. Three examples are given below. |
| 2895 | * |
| 2896 | * XXOOOOO (X can recapture but loses most of the string.) |
| 2897 | * X.XXXXO |
| 2898 | * ------- |
| 2899 | * |
| 2900 | * XXXOOOOOOOO (Like the previous example, except O loses one more stone) |
| 2901 | * XO*XXXXXXXO |
| 2902 | * ----------- |
| 2903 | * |
| 2904 | * XXXOO (After three captures, the lone X stone is gone.) |
| 2905 | * XO.XO |
| 2906 | * ----- |
| 2907 | * |
| 2908 | * This function is fast and never branches. There's little point in |
| 2909 | * caching the result. |
| 2910 | */ |
| 2911 | |
| 2912 | static int |
| 2913 | attack1(int str, int *move) |
| 2914 | { |
| 2915 | int color = board[str]; |
| 2916 | int other = OTHER_COLOR(color); |
| 2917 | int xpos; |
| 2918 | int savemove = 0; |
| 2919 | int savecode = 0; |
| 2920 | int liberties; |
| 2921 | int libs[6]; |
| 2922 | int k; |
| 2923 | int r; |
| 2924 | int adjs[MAXCHAIN]; |
| 2925 | int adj; |
| 2926 | int apos; |
| 2927 | |
| 2928 | |
| 2929 | SETUP_TRACE_INFO("attack1", str); |
| 2930 | reading_node_counter++; |
| 2931 | |
| 2932 | /* Pick up the position of the liberty. */ |
| 2933 | findlib(str, 1, &xpos); |
| 2934 | |
| 2935 | /* If the attacked string consists of more than one stone, the |
| 2936 | * attack never fails. (This assumes simple ko rule. With superko |
| 2937 | * rule it could still be a ko violation.) |
| 2938 | */ |
| 2939 | if (countstones(str) > 1) { |
| 2940 | RETURN_RESULT(WIN, xpos, move, "last liberty"); |
| 2941 | } |
| 2942 | |
| 2943 | /* Try to play on the liberty. This fails if and only if it is an |
| 2944 | * illegal ko capture. |
| 2945 | */ |
| 2946 | if (trymove(xpos, other, "attack1-A", str)) { |
| 2947 | /* Is the attacker in atari? If not the attack was successful. */ |
| 2948 | if (countlib(xpos) > 1) { |
| 2949 | popgo(); |
| 2950 | RETURN_RESULT(WIN, xpos, move, "last liberty"); |
| 2951 | } |
| 2952 | |
| 2953 | /* If the attacking string is also a single stone, a possible |
| 2954 | * recapture would be a ko violation, so the defender has to make |
| 2955 | * a ko threat first. |
| 2956 | */ |
| 2957 | else if (countstones(xpos) == 1) { |
| 2958 | if (get_komaster() != other) { |
| 2959 | /* If the defender is allowed to take the ko the result is KO_A. */ |
| 2960 | CHECK_RESULT_UNREVERSED(savecode, savemove, KO_A, xpos, move, |
| 2961 | "last liberty - ko"); |
| 2962 | } |
| 2963 | else { |
| 2964 | /* But if the attacker is the attack was successful. */ |
| 2965 | popgo(); |
| 2966 | RETURN_RESULT(WIN, xpos, move, "last liberty"); |
| 2967 | } |
| 2968 | } |
| 2969 | |
| 2970 | /* Otherwise, do recapture. Notice that the liberty must be |
| 2971 | * at (str) since we have already established that this string |
| 2972 | * was a single stone. |
| 2973 | */ |
| 2974 | else if (trymove(str, color, "attack1-B", str)) { |
| 2975 | /* If this was a proper snapback, (str) will now have more |
| 2976 | * than one liberty. |
| 2977 | */ |
| 2978 | if (countlib(str) > 1) { |
| 2979 | /* Proper snapback, attack fails. */ |
| 2980 | popgo(); |
| 2981 | } |
| 2982 | else { |
| 2983 | popgo(); |
| 2984 | popgo(); |
| 2985 | RETURN_RESULT(WIN, xpos, move, "last liberty"); |
| 2986 | } |
| 2987 | } |
| 2988 | popgo(); |
| 2989 | } |
| 2990 | else {/* Illegal ko capture. */ |
| 2991 | if (get_komaster() != color) { |
| 2992 | CHECK_RESULT_UNREVERSED(savecode, savemove, KO_B, xpos, move, |
| 2993 | "last liberty - ko"); |
| 2994 | } |
| 2995 | } |
| 2996 | |
| 2997 | /* If not yet successful, try backfilling and back-capturing. |
| 2998 | * An example of back-capturing can be found in reading:234. |
| 2999 | * Backfilling is maybe only meaningful in positions involving ko. |
| 3000 | */ |
| 3001 | liberties = approxlib(xpos, color, 6, libs); |
| 3002 | if (liberties <= 5) |
| 3003 | for (k = 0; k < liberties; k++) { |
| 3004 | apos = libs[k]; |
| 3005 | if (!is_self_atari(apos, other) |
| 3006 | && trymove(apos, other, "attack1-C", str)) { |
| 3007 | int dcode = do_find_defense(str, NULL); |
| 3008 | if (dcode != WIN && do_attack(str, NULL)) { |
| 3009 | if (dcode == 0) { |
| 3010 | popgo(); |
| 3011 | RETURN_RESULT(WIN, apos, move, "backfilling"); |
| 3012 | } |
| 3013 | UPDATE_SAVED_KO_RESULT(savecode, savemove, dcode, apos); |
| 3014 | } |
| 3015 | popgo(); |
| 3016 | } |
| 3017 | } |
| 3018 | |
| 3019 | adj = chainlinks2(str, adjs, 1); |
| 3020 | for (r = 0; r < adj; r++) { |
| 3021 | if (liberty_of_string(xpos, adjs[r])) { |
| 3022 | int adjs2[MAXCHAIN]; |
| 3023 | int adj2; |
| 3024 | adj2 = chainlinks2(adjs[r], adjs2, 1); |
| 3025 | for (k = 0; k < adj2; k++) { |
| 3026 | int ko_move; |
| 3027 | if (adjs2[k] == str) |
| 3028 | continue; |
| 3029 | findlib(adjs2[k], 1, &apos); |
| 3030 | if (komaster_trymove(apos, other, "attack1-D", str, |
| 3031 | &ko_move, stackp <= ko_depth && savecode == 0)) { |
| 3032 | if (!ko_move) { |
| 3033 | int dcode = do_find_defense(str, NULL); |
| 3034 | if (dcode != WIN |
| 3035 | && do_attack(str, NULL)) { |
| 3036 | popgo(); |
| 3037 | CHECK_RESULT(savecode, savemove, dcode, apos, move, |
| 3038 | "attack effective"); |
| 3039 | } |
| 3040 | else |
| 3041 | popgo(); |
| 3042 | } |
| 3043 | else { |
| 3044 | if (do_find_defense(str, NULL) != WIN |
| 3045 | && do_attack(str, NULL) != 0) { |
| 3046 | savemove = apos; |
| 3047 | savecode = KO_B; |
| 3048 | } |
| 3049 | popgo(); |
| 3050 | } |
| 3051 | } |
| 3052 | } |
| 3053 | } |
| 3054 | } |
| 3055 | |
| 3056 | if (savecode == 0) { |
| 3057 | RETURN_RESULT(0, 0, move, NULL); |
| 3058 | } |
| 3059 | |
| 3060 | RETURN_RESULT(savecode, savemove, move, "saved move"); |
| 3061 | } |
| 3062 | |
| 3063 | |
| 3064 | /* If str points to a group with exactly two liberties |
| 3065 | * attack2 determines whether it can be captured in ladder or net. |
| 3066 | * If yes, *move is the killing move. move may be null if caller |
| 3067 | * is only interested in whether it can be captured. |
| 3068 | * |
| 3069 | * Returns KO_A or KO_B if it can be killed conditioned on ko. Returns |
| 3070 | * KO_A if it can be killed provided (other) is willing to ignore any |
| 3071 | * ko threat. Returns KO_B if (other) wins provided he has a ko threat |
| 3072 | * which must be answered. Can give a return code KO_B yet *move=0 if |
| 3073 | * the winning move is an illegal ko capture. In this case, making a |
| 3074 | * ko threat and having it answered should transform the position to |
| 3075 | * one where the return code is KO_A. |
| 3076 | * |
| 3077 | * See the comment before defend1 about ladders and reading depth. |
| 3078 | */ |
| 3079 | |
| 3080 | static int |
| 3081 | attack2(int str, int *move) |
| 3082 | { |
| 3083 | int color = board[str]; |
| 3084 | int other = OTHER_COLOR(color); |
| 3085 | int hpos; |
| 3086 | int xpos = NO_MOVE; |
| 3087 | int liberties, r; |
| 3088 | int libs[2]; |
| 3089 | int libs2[2]; |
| 3090 | int adj, adjs[MAXCHAIN]; |
| 3091 | int savemove = 0; |
| 3092 | int savecode = 0; |
| 3093 | int k; |
| 3094 | int atari_possible = 0; |
| 3095 | struct reading_moves moves; |
| 3096 | int adjacent_liberties = 0; |
| 3097 | int pass; |
| 3098 | int suggest_move = NO_MOVE; |
| 3099 | |
| 3100 | SETUP_TRACE_INFO("attack2", str); |
| 3101 | reading_node_counter++; |
| 3102 | moves.num = 0; |
| 3103 | moves.num_tried = 0; |
| 3104 | |
| 3105 | str = find_origin(str); |
| 3106 | ASSERT1(IS_STONE(board[str]), str); |
| 3107 | ASSERT1(countlib(str) == 2, str); |
| 3108 | |
| 3109 | for (pass = 0; pass < 4; pass++) { |
| 3110 | |
| 3111 | switch (pass) { |
| 3112 | case 0: |
| 3113 | /* The attack may fail if a boundary string is in atari and cannot |
| 3114 | * be defended. First we must try defending such a string. |
| 3115 | * |
| 3116 | * We start by trying to defend the boundary string by looking for an |
| 3117 | * adjacent string which is in atari. |
| 3118 | */ |
| 3119 | adj = chainlinks2(str, adjs, 1); |
| 3120 | for (r = 0; r < adj; r++) { |
| 3121 | /* If stackp > depth and any boundary chain is in atari, assume safe. |
| 3122 | * However, if the captured chain is only of size 1, there can still |
| 3123 | * be a working ladder, so continue if that is the case. |
| 3124 | * Also if the string in atari shares its liberty with the |
| 3125 | * attacked string, drawing it out may enable the ladder to |
| 3126 | * continue. |
| 3127 | */ |
| 3128 | if (stackp > depth |
| 3129 | && countstones(adjs[r]) > 1 |
| 3130 | && !have_common_lib(str, adjs[r], NULL)) { |
| 3131 | RETURN_RESULT(0, 0, move, "boundary in atari"); |
| 3132 | } |
| 3133 | |
| 3134 | /* Pick up moves breaking the second order chain. */ |
| 3135 | if (stackp <= depth) |
| 3136 | break_chain_moves(adjs[r], &moves); |
| 3137 | |
| 3138 | findlib(adjs[r], 1, &hpos); |
| 3139 | ADD_CANDIDATE_MOVE(hpos, 0, moves, "save_boundary"); |
| 3140 | } |
| 3141 | |
| 3142 | /* Get the two liberties of (str). */ |
| 3143 | liberties = findlib(str, 2, libs); |
| 3144 | ASSERT1(liberties == 2, str); |
| 3145 | |
| 3146 | if (DIRECT_NEIGHBORS(libs[0], libs[1])) |
| 3147 | adjacent_liberties = 1; |
| 3148 | |
| 3149 | for (k = 0; k < 2; k++) { |
| 3150 | int apos = libs[k]; |
| 3151 | if (!is_self_atari(apos, other)) |
| 3152 | atari_possible = 1; |
| 3153 | /* We only want to consider the move at (apos) if: |
| 3154 | * stackp <= backfill_depth |
| 3155 | * -or- stackp <= depth and it is an isolated stone |
| 3156 | * -or- it is not in immediate atari |
| 3157 | */ |
| 3158 | if (stackp <= backfill_depth |
| 3159 | || ((stackp <= depth || adjacent_liberties) |
| 3160 | && !has_neighbor(apos, other)) |
| 3161 | || !is_self_atari(apos, other)) |
| 3162 | ADD_CANDIDATE_MOVE(apos, 0, moves, "liberty"); |
| 3163 | |
| 3164 | /* Try backfilling if atari is impossible. */ |
| 3165 | if (stackp <= backfill_depth |
| 3166 | && approxlib(apos, other, 2, libs2) == 1) { |
| 3167 | ADD_CANDIDATE_MOVE(libs2[0], 0, moves, "backfill"); |
| 3168 | /* If there is a neighbor in atari, we also try back-capturing. */ |
| 3169 | for (r = 0; r < 4; r++) { |
| 3170 | int bpos = libs2[0] + delta[r]; |
| 3171 | if (board[bpos] == other && chainlinks2(bpos, adjs, 1) > 0) { |
| 3172 | /* FIXME: If there is more than one neighbor in atari, we |
| 3173 | * currently just take one randomly. This is maybe not good |
| 3174 | * enough. We might also want to check against snapback. |
| 3175 | * |
| 3176 | * FIXME: What is the purpose of this? It produces some |
| 3177 | * completely irrelevant moves (e.g. if bpos is a huge string |
| 3178 | * with many liberties and adjs[0] is somewhere else on the |
| 3179 | * board). |
| 3180 | */ |
| 3181 | findlib(adjs[0], 1, &xpos); |
| 3182 | ADD_CANDIDATE_MOVE(xpos, 0, moves, "back-capture"); |
| 3183 | } |
| 3184 | } |
| 3185 | } |
| 3186 | } |
| 3187 | |
| 3188 | /* If we can't make a direct atari, look for edge blocking moves. */ |
| 3189 | if (!atari_possible) |
| 3190 | for (k = 0; k < 2; k++) |
| 3191 | edge_block_moves(str, libs[k], &moves); |
| 3192 | |
| 3193 | |
| 3194 | /* If one of the surrounding chains have only two liberties, which |
| 3195 | * coincide with the liberties of the attacked string, we try to |
| 3196 | * backcapture. |
| 3197 | */ |
| 3198 | |
| 3199 | adj = chainlinks2(str, adjs, 2); |
| 3200 | for (r = 0; r < adj; r++) { |
| 3201 | int apos = adjs[r]; |
| 3202 | if (liberty_of_string(libs[0], apos) |
| 3203 | && liberty_of_string(libs[1], apos)) |
| 3204 | break_chain_moves(apos, &moves); |
| 3205 | } |
| 3206 | |
| 3207 | propose_edge_moves(str, libs, liberties, &moves, other); |
| 3208 | |
| 3209 | break; |
| 3210 | |
| 3211 | case 1: |
| 3212 | if (stackp <= backfill_depth) { |
| 3213 | special_attack2_moves(str, libs, &moves); |
| 3214 | special_attack3_moves(str, libs, &moves); |
| 3215 | special_attack4_moves(str, libs, &moves); |
| 3216 | } |
| 3217 | break; |
| 3218 | |
| 3219 | case 2: |
| 3220 | find_cap_moves(str, &moves); |
| 3221 | break; |
| 3222 | |
| 3223 | case 3: |
| 3224 | /* If it is not possible to make a direct atari, we try filling |
| 3225 | * a liberty of the superstring. |
| 3226 | */ |
| 3227 | if (get_level() >= 8 |
| 3228 | && stackp <= backfill_depth |
| 3229 | && (stackp <= superstring_depth || !atari_possible)) { |
| 3230 | int liberty_cap = 2; |
| 3231 | if (stackp <= backfill2_depth) |
| 3232 | liberty_cap = 3; |
| 3233 | superstring_moves(str, &moves, liberty_cap, 1); |
| 3234 | squeeze_moves(str, &moves); |
| 3235 | } |
| 3236 | break; |
| 3237 | |
| 3238 | default: |
| 3239 | abort(); |
| 3240 | } /* switch (pass) */ |
| 3241 | |
| 3242 | order_moves(str, &moves, other, read_function_name, *move); |
| 3243 | ATTACK_TRY_MOVES(0, &suggest_move); |
| 3244 | } |
| 3245 | |
| 3246 | RETURN_RESULT(savecode, savemove, move, "saved move"); |
| 3247 | } |
| 3248 | |
| 3249 | |
| 3250 | |
| 3251 | /* attack3(str, *move) is used when (str) points to a group with |
| 3252 | * three liberties. It returns true if it finds a way to kill the group. |
| 3253 | * |
| 3254 | * Return code is KO_A if the group can be killed if the attacker is |
| 3255 | * willing to ignore any ko threat. |
| 3256 | * |
| 3257 | * Return code is KO_B if the group can be killed if the attacker is |
| 3258 | * able to find a ko threat which must be answered. |
| 3259 | * |
| 3260 | * If non-NULL (*move) will be set to the move which makes the |
| 3261 | * attack succeed. |
| 3262 | */ |
| 3263 | |
| 3264 | static int |
| 3265 | attack3(int str, int *move) |
| 3266 | { |
| 3267 | int color = board[str]; |
| 3268 | int other = OTHER_COLOR(color); |
| 3269 | int adj, adjs[MAXCHAIN]; |
| 3270 | int liberties; |
| 3271 | int libs[3]; |
| 3272 | int r; |
| 3273 | int k; |
| 3274 | struct reading_moves moves; |
| 3275 | int savemove = 0; |
| 3276 | int savecode = 0; |
| 3277 | int pass; |
| 3278 | int suggest_move = NO_MOVE; |
| 3279 | |
| 3280 | SETUP_TRACE_INFO("attack3", str); |
| 3281 | reading_node_counter++; |
| 3282 | moves.num = 0; |
| 3283 | moves.num_tried = 0; |
| 3284 | |
| 3285 | ASSERT1(IS_STONE(board[str]), str); |
| 3286 | |
| 3287 | ASSERT1(stackp <= depth, str); |
| 3288 | |
| 3289 | for (pass = 0; pass < 4; pass++) { |
| 3290 | |
| 3291 | switch (pass) { |
| 3292 | case 0: |
| 3293 | adj = chainlinks2(str, adjs, 1); |
| 3294 | for (r = 0; r < adj; r++) { |
| 3295 | int hpos; |
| 3296 | break_chain_moves(adjs[r], &moves); |
| 3297 | |
| 3298 | findlib(adjs[r], 1, &hpos); |
| 3299 | ADD_CANDIDATE_MOVE(hpos, 0, moves, "save_boundary"); |
| 3300 | } |
| 3301 | |
| 3302 | /* Defend against double atari in the surrounding chain early. */ |
| 3303 | double_atari_chain2_moves(str, &moves, stackp <= superstring_depth); |
| 3304 | |
| 3305 | /* Get the three liberties of (str). */ |
| 3306 | liberties = findlib(str, 3, libs); |
| 3307 | ASSERT1(liberties == 3, str); |
| 3308 | |
| 3309 | for (k = 0; k < 3; k++) { |
| 3310 | #if 0 |
| 3311 | int libs2[2]; |
| 3312 | #endif |
| 3313 | int apos = libs[k]; |
| 3314 | /* We only want to consider the move at (apos) if: |
| 3315 | * stackp <= backfill_depth |
| 3316 | * -or- stackp <= depth and it is an isolated stone |
| 3317 | * -or- it is not in immediate atari |
| 3318 | */ |
| 3319 | if (stackp <= backfill_depth |
| 3320 | || (stackp <= depth |
| 3321 | && !has_neighbor(apos, other)) |
| 3322 | || !is_self_atari(apos, other)) |
| 3323 | ADD_CANDIDATE_MOVE(apos, 0, moves, "liberty"); |
| 3324 | |
| 3325 | edge_closing_backfill_moves(str, apos, &moves); |
| 3326 | |
| 3327 | #if 0 |
| 3328 | /* Try backfilling if atari is impossible. */ |
| 3329 | if (stackp <= backfill_depth |
| 3330 | && approxlib(apos, other, 2, libs2) == 1) { |
| 3331 | ADD_CANDIDATE_MOVE(libs2[0], 0, moves, "backfill"); |
| 3332 | } |
| 3333 | #endif |
| 3334 | |
| 3335 | /* Look for edge blocking moves. */ |
| 3336 | edge_block_moves(str, apos, &moves); |
| 3337 | } |
| 3338 | |
| 3339 | /* Pick up some edge moves. */ |
| 3340 | propose_edge_moves(str, libs, liberties, &moves, other); |
| 3341 | break; |
| 3342 | |
| 3343 | case 1: |
| 3344 | /* The simple ataris didn't work. Try something more fancy. */ |
| 3345 | if (stackp <= backfill_depth) |
| 3346 | find_cap_moves(str, &moves); |
| 3347 | |
| 3348 | if (stackp <= fourlib_depth) |
| 3349 | draw_back_moves(str, &moves); |
| 3350 | |
| 3351 | break; |
| 3352 | |
| 3353 | case 2: |
| 3354 | /* Try to defend chain links with two liberties. */ |
| 3355 | if (stackp <= backfill2_depth) { |
| 3356 | adj = chainlinks2(str, adjs, 2); |
| 3357 | for (r = 0; r < adj; r++) { |
| 3358 | int libs2[2]; |
| 3359 | findlib(adjs[r], 2, libs2); |
| 3360 | if (approxlib(libs2[0], other, 4, NULL) > 3 |
| 3361 | && approxlib(libs2[1], other, 4, NULL) > 3) |
| 3362 | continue; |
| 3363 | break_chain_moves(adjs[r], &moves); |
| 3364 | break_chain2_moves(adjs[r], &moves, 1, 0); |
| 3365 | for (k = 0; k < 2; k++) |
| 3366 | ADD_CANDIDATE_MOVE(libs2[k], 0, moves, "save_boundary-2"); |
| 3367 | } |
| 3368 | } |
| 3369 | break; |
| 3370 | |
| 3371 | case 3: |
| 3372 | /* If nothing else works, we try filling a liberty of the |
| 3373 | * super_string. |
| 3374 | */ |
| 3375 | if (get_level() >= 8 && stackp <= backfill2_depth) { |
| 3376 | superstring_moves(str, &moves, 3, 1); |
| 3377 | squeeze_moves(str, &moves); |
| 3378 | } |
| 3379 | break; |
| 3380 | |
| 3381 | default: |
| 3382 | abort(); |
| 3383 | } |
| 3384 | |
| 3385 | order_moves(str, &moves, other, read_function_name, *move); |
| 3386 | ATTACK_TRY_MOVES(1, &suggest_move); |
| 3387 | } /* for (pass... */ |
| 3388 | |
| 3389 | RETURN_RESULT(savecode, savemove, move, "saved move"); |
| 3390 | } |
| 3391 | |
| 3392 | |
| 3393 | /* attack4 tries to capture a string with 4 liberties. */ |
| 3394 | |
| 3395 | static int |
| 3396 | attack4(int str, int *move) |
| 3397 | { |
| 3398 | int color = board[str]; |
| 3399 | int other = OTHER_COLOR(color); |
| 3400 | int r; |
| 3401 | int k; |
| 3402 | int liberties; |
| 3403 | int libs[4]; |
| 3404 | int adj, adjs[MAXCHAIN]; |
| 3405 | struct reading_moves moves; |
| 3406 | int savemove = 0; |
| 3407 | int savecode = 0; |
| 3408 | int pass; |
| 3409 | int suggest_move = NO_MOVE; |
| 3410 | |
| 3411 | SETUP_TRACE_INFO("attack4", str); |
| 3412 | |
| 3413 | ASSERT1(IS_STONE(board[str]), str); |
| 3414 | reading_node_counter++; |
| 3415 | moves.num = 0; |
| 3416 | moves.num_tried = 0; |
| 3417 | |
| 3418 | if (stackp > depth) { |
| 3419 | SGFTRACE(0, 0, "stackp > depth"); |
| 3420 | return 0; |
| 3421 | } |
| 3422 | |
| 3423 | for (pass = 0; pass < 2; pass++) { |
| 3424 | |
| 3425 | switch (pass) { |
| 3426 | case 0: |
| 3427 | adj = chainlinks2(str, adjs, 1); |
| 3428 | for (r = 0; r < adj; r++) { |
| 3429 | int hpos; |
| 3430 | break_chain_moves(adjs[r], &moves); |
| 3431 | |
| 3432 | findlib(adjs[r], 1, &hpos); |
| 3433 | ADD_CANDIDATE_MOVE(hpos, 0, moves, "save_boundary"); |
| 3434 | } |
| 3435 | |
| 3436 | /* Defend against double atari in the surrounding chain early. */ |
| 3437 | double_atari_chain2_moves(str, &moves, stackp <= superstring_depth); |
| 3438 | |
| 3439 | /* Give a score bonus to the chain preserving moves. */ |
| 3440 | for (k = 0; k < moves.num; k++) |
| 3441 | moves.score[k] += 5; |
| 3442 | |
| 3443 | /* Get the four liberties of (str). */ |
| 3444 | liberties = findlib(str, 4, libs); |
| 3445 | ASSERT1(liberties == 4, str); |
| 3446 | |
| 3447 | for (k = 0; k < 4; k++) { |
| 3448 | int apos = libs[k]; |
| 3449 | /* We only want to consider the move at (apos) if: |
| 3450 | * stackp <= backfill_depth |
| 3451 | * -or- stackp <= depth and it is an isolated stone |
| 3452 | * -or- it is not in immediate atari |
| 3453 | */ |
| 3454 | if (stackp <= backfill_depth |
| 3455 | || (stackp <= depth |
| 3456 | && !has_neighbor(apos, other)) |
| 3457 | || !is_self_atari(apos, other)) |
| 3458 | ADD_CANDIDATE_MOVE(apos, 0, moves, "liberty"); |
| 3459 | |
| 3460 | edge_closing_backfill_moves(str, apos, &moves); |
| 3461 | |
| 3462 | /* Look for edge blocking moves. */ |
| 3463 | edge_block_moves(str, apos, &moves); |
| 3464 | } |
| 3465 | |
| 3466 | /* Pick up some edge moves. */ |
| 3467 | propose_edge_moves(str, libs, liberties, &moves, other); |
| 3468 | break; |
| 3469 | |
| 3470 | case 1: |
| 3471 | if (stackp <= backfill_depth) |
| 3472 | find_cap_moves(str, &moves); |
| 3473 | break; |
| 3474 | |
| 3475 | default: |
| 3476 | abort(); |
| 3477 | } |
| 3478 | |
| 3479 | order_moves(str, &moves, other, read_function_name, *move); |
| 3480 | ATTACK_TRY_MOVES(1, &suggest_move); |
| 3481 | } /* for (pass = ... */ |
| 3482 | |
| 3483 | RETURN_RESULT(savecode, savemove, move, "saved move"); |
| 3484 | } |
| 3485 | |
| 3486 | |
| 3487 | /* If (str) points to a string with 2 - 4 liberties, |
| 3488 | * find_cap_moves(str, &moves) |
| 3489 | * looks for a configuration of the following type: |
| 3490 | * |
| 3491 | * Xa |
| 3492 | * b* |
| 3493 | * |
| 3494 | * where X are elements of the string in question and a and b are |
| 3495 | * two of its liberties. |
| 3496 | * |
| 3497 | * For larger strings, this can find moves like |
| 3498 | * |
| 3499 | * XXXXX |
| 3500 | * XX.XX |
| 3501 | * X.*.X |
| 3502 | * XX.XX |
| 3503 | * XXXXX |
| 3504 | * |
| 3505 | * even though they are not capping moves. |
| 3506 | */ |
| 3507 | |
| 3508 | static void |
| 3509 | find_cap_moves(int str, struct reading_moves *moves) |
| 3510 | { |
| 3511 | int alib, blib; |
| 3512 | int numlibs; |
| 3513 | int libs[4]; |
| 3514 | int i, j; |
| 3515 | int ai, aj; |
| 3516 | int bi, bj; |
| 3517 | |
| 3518 | numlibs = findlib(str, 4, libs); |
| 3519 | if (numlibs > 4 || numlibs < 2) |
| 3520 | return; |
| 3521 | |
| 3522 | for (i = 0; i < numlibs - 1; i++) { |
| 3523 | for (j = i + 1; j < numlibs; j++) { |
| 3524 | alib = libs[i]; |
| 3525 | blib = libs[j]; |
| 3526 | |
| 3527 | /* Check if the two liberties are located like the figure above. */ |
| 3528 | if (!DIAGONAL_NEIGHBORS(alib, blib)) |
| 3529 | continue; |
| 3530 | |
| 3531 | ai = I(alib); |
| 3532 | aj = J(alib); |
| 3533 | bi = I(blib); |
| 3534 | bj = J(blib); |
| 3535 | /* Which of the two corner points should we use? One of them is |
| 3536 | * always occupied by the string at (str), the other one is either |
| 3537 | * free or occupied by something else. |
| 3538 | */ |
| 3539 | if (BOARD(bi, aj) == EMPTY) |
| 3540 | ADD_CANDIDATE_MOVE(POS(bi, aj), 10, *moves, "find_cap"); |
| 3541 | else if (BOARD(ai, bj) == EMPTY) |
| 3542 | ADD_CANDIDATE_MOVE(POS(ai, bj), 10, *moves, "find_cap"); |
| 3543 | } |
| 3544 | } |
| 3545 | } |
| 3546 | |
| 3547 | |
| 3548 | |
| 3549 | /* In a situation like this: |
| 3550 | * |
| 3551 | * ----- the code that |
| 3552 | * cO.OX follows can find |
| 3553 | * XXOOX the attacking move |
| 3554 | * XO.OX at c. |
| 3555 | * XOOOX |
| 3556 | * XXXXX |
| 3557 | * |
| 3558 | * The name of the function corresponds to special_rescue2, which is |
| 3559 | * fairly similar to this situation. |
| 3560 | */ |
| 3561 | |
| 3562 | static void |
| 3563 | special_attack2_moves(int str, int libs[2], struct reading_moves *moves) |
| 3564 | { |
| 3565 | int color = board[str]; |
| 3566 | int other = OTHER_COLOR(color); |
| 3567 | int newlibs[3]; |
| 3568 | int xpos; |
| 3569 | int k; |
| 3570 | |
| 3571 | for (k = 0; k < 2; k++) { |
| 3572 | if (is_suicide(libs[k], other) |
| 3573 | && (approxlib(libs[k], color, 3, newlibs) == 2)) { |
| 3574 | if (newlibs[0] != libs[1-k]) |
| 3575 | xpos = newlibs[0]; |
| 3576 | else |
| 3577 | xpos = newlibs[1]; |
| 3578 | |
| 3579 | if (!is_self_atari(xpos, other)) { |
| 3580 | ADD_CANDIDATE_MOVE(xpos, 0, *moves, "special_attack2"); |
| 3581 | } |
| 3582 | } |
| 3583 | } |
| 3584 | } |
| 3585 | |
| 3586 | |
| 3587 | /* In situations like these: |
| 3588 | * |
| 3589 | * ..XXX.. ...XX |
| 3590 | * .XX.XX. .cO.X |
| 3591 | * XXOOOXX ....X |
| 3592 | * XO.O.OX XOOXX |
| 3593 | * XO.c.OX XXXX. |
| 3594 | * ------- |
| 3595 | * |
| 3596 | * the code that follows can find the attacking move at c. |
| 3597 | */ |
| 3598 | |
| 3599 | static void |
| 3600 | special_attack3_moves(int str, int libs[2], struct reading_moves *moves) |
| 3601 | { |
| 3602 | int color = board[str]; |
| 3603 | int other = OTHER_COLOR(color); |
| 3604 | int xpos; |
| 3605 | int apos; |
| 3606 | int bpos; |
| 3607 | int k; |
| 3608 | |
| 3609 | ASSERT1(countlib(str) == 2, str); |
| 3610 | |
| 3611 | for (k = 0; k < 2; k++) { |
| 3612 | apos = libs[k]; |
| 3613 | bpos = libs[1-k]; |
| 3614 | |
| 3615 | if (apos == SOUTH(bpos) || apos == NORTH(bpos)) { |
| 3616 | if (board[WEST(apos)] == EMPTY) |
| 3617 | xpos = WEST(apos); |
| 3618 | else if (board[EAST(apos)] == EMPTY) |
| 3619 | xpos = EAST(apos); |
| 3620 | else |
| 3621 | continue; |
| 3622 | } |
| 3623 | else if (apos == WEST(bpos) || apos == EAST(bpos)) { |
| 3624 | if (board[SOUTH(apos)] == EMPTY) |
| 3625 | xpos = SOUTH(apos); |
| 3626 | else if (board[NORTH(apos)] == EMPTY) |
| 3627 | xpos = NORTH(apos); |
| 3628 | else |
| 3629 | continue; |
| 3630 | } |
| 3631 | else |
| 3632 | return; /* Incorrect configuration, give up. */ |
| 3633 | |
| 3634 | if (!is_self_atari(xpos, other)) |
| 3635 | ADD_CANDIDATE_MOVE(xpos, 0, *moves, "special_attack3"); |
| 3636 | } |
| 3637 | } |
| 3638 | |
| 3639 | |
| 3640 | /* In situations like these: |
| 3641 | * |
| 3642 | * ...O.O... ...O.O... |
| 3643 | * XXXXOOXXX XXXXOOXXX |
| 3644 | * XOOOXXO*. Xsssbbcd. |
| 3645 | * .X.O..... .X.sa.e.. |
| 3646 | * --------- --------- |
| 3647 | * |
| 3648 | * the code that follows can find the attacking move at *. |
| 3649 | * |
| 3650 | * Also for situations in which c has three liberties, one of which in common |
| 3651 | * with b, the respective attacking move is found (see reading:52 for an |
| 3652 | * example). |
| 3653 | */ |
| 3654 | |
| 3655 | static void |
| 3656 | special_attack4_moves(int str, int libs[2], struct reading_moves *moves) |
| 3657 | { |
| 3658 | int color = board[str]; |
| 3659 | int other = OTHER_COLOR(color); |
| 3660 | int adj, adjs[MAXCHAIN]; |
| 3661 | int adj2, adjs2[MAXCHAIN]; |
| 3662 | int libs2[3]; |
| 3663 | int apos; |
| 3664 | int bpos = 0; |
| 3665 | int cpos; |
| 3666 | int dpos; |
| 3667 | int epos; |
| 3668 | int clibs; |
| 3669 | int dlibs; |
| 3670 | int elibs; |
| 3671 | int bc_common_lib; |
| 3672 | int k, s, t, u; |
| 3673 | |
| 3674 | ASSERT1(countlib(str) == 2, str); |
| 3675 | |
| 3676 | /* To avoid making this too general, we require that both |
| 3677 | * liberties are self ataris for X. |
| 3678 | */ |
| 3679 | if (!is_self_atari(libs[0], other) |
| 3680 | || !is_self_atari(libs[1], other)) |
| 3681 | return; |
| 3682 | |
| 3683 | /* Pick up chain links with 2 liberties. */ |
| 3684 | adj = chainlinks2(str, adjs, 2); |
| 3685 | |
| 3686 | for (k = 0; k < 2; k++) { |
| 3687 | apos = libs[k]; |
| 3688 | |
| 3689 | /* Check that (apos) also is a liberty of one of the two liberty |
| 3690 | * chain links. |
| 3691 | */ |
| 3692 | for (s = 0; s < adj; s++) |
| 3693 | if (liberty_of_string(apos, adjs[s])) { |
| 3694 | bpos = adjs[s]; |
| 3695 | break; |
| 3696 | } |
| 3697 | |
| 3698 | /* Nothing found. */ |
| 3699 | if (s == adj) |
| 3700 | continue; |
| 3701 | |
| 3702 | /* Now require that (bpos) has a chain link, different from (str), |
| 3703 | * also with two liberties, or with three liberties, but one in common |
| 3704 | * with (bpos). |
| 3705 | */ |
| 3706 | adj2 = chainlinks3(bpos, adjs2, 3); |
| 3707 | |
| 3708 | for (s = 0; s < adj2; s++) { |
| 3709 | cpos = adjs2[s]; |
| 3710 | if (same_string(cpos, str)) |
| 3711 | continue; |
| 3712 | |
| 3713 | /* Pick up the liberties of (cpos). */ |
| 3714 | clibs = findlib(cpos, 3, libs2); |
| 3715 | |
| 3716 | /* No need to do something fancy if it is in atari already. */ |
| 3717 | if (clibs < 2) |
| 3718 | continue; |
| 3719 | |
| 3720 | /* (cpos) has three liberties, none of which in commmon with (bpos) |
| 3721 | * attacking it seems too difficult. */ |
| 3722 | bc_common_lib = have_common_lib(bpos, cpos, NULL); |
| 3723 | if (clibs > 2 && !bc_common_lib) |
| 3724 | continue; |
| 3725 | |
| 3726 | /* Try playing at a liberty. Before doing this, verify that |
| 3727 | * (cpos) cannot get more than three liberties by answering on |
| 3728 | * another liberty and that we are not putting ourselves in atari. |
| 3729 | * We also should only allow ourselves to get fewer liberties than |
| 3730 | * the defender in case (bpos) and (cpos) have a common liberty. |
| 3731 | */ |
| 3732 | for (t = 0; t < clibs; t++) { |
| 3733 | dpos = libs2[t]; |
| 3734 | |
| 3735 | if (is_self_atari(dpos, other)) |
| 3736 | continue; |
| 3737 | |
| 3738 | for (u = 0; u < clibs; u++) { |
| 3739 | if (t == u) |
| 3740 | continue; |
| 3741 | |
| 3742 | epos = libs2[u]; |
| 3743 | |
| 3744 | elibs = approxlib(epos, color, 4, NULL); |
| 3745 | if (elibs > 3) |
| 3746 | break; |
| 3747 | |
| 3748 | dlibs = approxlib(dpos, other, 3, NULL); |
| 3749 | if (elibs > dlibs && !bc_common_lib) |
| 3750 | break; |
| 3751 | } |
| 3752 | |
| 3753 | if (u >= clibs) /* No break occurred. */ |
| 3754 | ADD_CANDIDATE_MOVE(dpos, 0, *moves, "special_attack4"); |
| 3755 | } |
| 3756 | } |
| 3757 | } |
| 3758 | } |
| 3759 | |
| 3760 | |
| 3761 | /* |
| 3762 | * If (str) points to a string, draw_back(str, &moves) |
| 3763 | * looks for a move in the following configuration which attacks |
| 3764 | * the string: |
| 3765 | * |
| 3766 | * X* X=attacker, O=defender |
| 3767 | * O. |
| 3768 | * |
| 3769 | * In the initial implementation we consider cases |
| 3770 | * where X has exactly 2 liberties. |
| 3771 | * |
| 3772 | */ |
| 3773 | |
| 3774 | static void |
| 3775 | draw_back_moves(int str, struct reading_moves *moves) |
| 3776 | { |
| 3777 | int r, k; |
| 3778 | int adj, adjs[MAXCHAIN]; |
| 3779 | int libs[2]; |
| 3780 | |
| 3781 | adj = chainlinks2(str, adjs, 2); |
| 3782 | for (r = 0; r < adj; r++) { |
| 3783 | findlib(adjs[r], 2, libs); |
| 3784 | for (k = 0; k < 2; k++) { |
| 3785 | if (!liberty_of_string(libs[k], str) |
| 3786 | && ((ON_BOARD1(SOUTH(libs[k])) |
| 3787 | && liberty_of_string(SOUTH(libs[k]), str)) |
| 3788 | || (ON_BOARD1(WEST(libs[k])) |
| 3789 | && liberty_of_string(WEST(libs[k]), str)) |
| 3790 | || (ON_BOARD1(NORTH(libs[k])) |
| 3791 | && liberty_of_string(NORTH(libs[k]), str)) |
| 3792 | || (ON_BOARD1(EAST(libs[k])) |
| 3793 | && liberty_of_string(EAST(libs[k]), str)))) { |
| 3794 | ADD_CANDIDATE_MOVE(libs[k], 0, *moves, "draw_back"); |
| 3795 | } |
| 3796 | } |
| 3797 | } |
| 3798 | } |
| 3799 | |
| 3800 | /* In the following position the reading is much simplifed if we start |
| 3801 | * with the edge closing backfilling move at *. |
| 3802 | * |
| 3803 | * |OO... |
| 3804 | * |.OOO. |
| 3805 | * |.X.O. |
| 3806 | * |XXXO. |
| 3807 | * |.X.*. |
| 3808 | * +----- |
| 3809 | * |
| 3810 | * This function identifies the situation |
| 3811 | * |
| 3812 | * ?XOb |
| 3813 | * Xatc |
| 3814 | * ---- |
| 3815 | * |
| 3816 | * where a is a liberty of the attacked string, t is the proposed move, |
| 3817 | * and b and c do not contain more O stones than X stones. |
| 3818 | */ |
| 3819 | |
| 3820 | static void |
| 3821 | edge_closing_backfill_moves(int str, int apos, struct reading_moves *moves) |
| 3822 | { |
| 3823 | int color = board[str]; |
| 3824 | int other = OTHER_COLOR(color); |
| 3825 | int k; |
| 3826 | int bpos; |
| 3827 | int cpos; |
| 3828 | int number_x, number_o; |
| 3829 | |
| 3830 | for (k = 0; k < 4; k++) { |
| 3831 | int up = delta[k]; |
| 3832 | int right = delta[(k+1)%4]; |
| 3833 | if (ON_BOARD(apos - up)) |
| 3834 | continue; |
| 3835 | if (board[apos + up] != color) |
| 3836 | return; |
| 3837 | if (board[apos + right] == EMPTY |
| 3838 | && (!ON_BOARD(apos - right) |
| 3839 | || board[apos - right] == color)) |
| 3840 | ; /* Everything ok so far. */ |
| 3841 | else if (board[apos - right] == EMPTY |
| 3842 | && (!ON_BOARD(apos + right) |
| 3843 | || board[apos + right] == color)) { |
| 3844 | /* Negate right direction. */ |
| 3845 | right = -right; |
| 3846 | } |
| 3847 | else |
| 3848 | return; |
| 3849 | |
| 3850 | if (board[apos + up + right] != other) |
| 3851 | return; |
| 3852 | |
| 3853 | bpos = apos + up + 2 * right; |
| 3854 | if (!ON_BOARD(bpos)) |
| 3855 | return; |
| 3856 | |
| 3857 | cpos = apos + 2 * right; |
| 3858 | |
| 3859 | number_x = 0; |
| 3860 | number_o = 0; |
| 3861 | if (board[bpos] == color) |
| 3862 | number_x++; |
| 3863 | else if (board[bpos] == other) |
| 3864 | number_o++; |
| 3865 | |
| 3866 | if (board[cpos] == color) |
| 3867 | number_x++; |
| 3868 | else if (board[cpos] == other) |
| 3869 | number_o++; |
| 3870 | |
| 3871 | if (number_o > number_x) |
| 3872 | return; |
| 3873 | |
| 3874 | ADD_CANDIDATE_MOVE(apos + right, 0, *moves, "edge_closing_backfill"); |
| 3875 | return; |
| 3876 | } |
| 3877 | } |
| 3878 | |
| 3879 | |
| 3880 | /* The first version of this function seemed to induce too many |
| 3881 | * variations and has therefore been replaced by a much more limited |
| 3882 | * version. |
| 3883 | */ |
| 3884 | #if 0 |
| 3885 | |
| 3886 | /* In positions like |
| 3887 | * |
| 3888 | * OO... |
| 3889 | * XXO*. |
| 3890 | * x.X*. |
| 3891 | * ----- |
| 3892 | * |
| 3893 | * where the X stones to the left are being attacked, it is often a |
| 3894 | * good idea to first consider either or both of the moves marked by * |
| 3895 | * in the diagram. Notice that propose_edge_moves() doesn't help with |
| 3896 | * this, since the rightmost X stone is not part of the attacked |
| 3897 | * string, only the corresponding superstring. |
| 3898 | * |
| 3899 | * This function identifies the situation |
| 3900 | * |
| 3901 | * ?XO.? ?bdf? |
| 3902 | * ?.X.o haceg |
| 3903 | * ----- ----- |
| 3904 | * |
| 3905 | * where a is a liberty of the attacked string, b is a stone of the |
| 3906 | * attacked string, and e and f are the considered moves. Also |
| 3907 | * considered is the situation where the conditions to the right are |
| 3908 | * not correct but c has only two liberties anyway. If safe, the move |
| 3909 | * to make atari on c is proposed. |
| 3910 | * |
| 3911 | * Notice, this code is disabled, as commented above. |
| 3912 | */ |
| 3913 | |
| 3914 | static void |
| 3915 | edge_block_moves(int str, int apos, struct reading_moves *moves) |
| 3916 | { |
| 3917 | int color = board[str]; |
| 3918 | int other = OTHER_COLOR(color); |
| 3919 | int cpos; |
| 3920 | int dpos; |
| 3921 | int epos; |
| 3922 | int fpos; |
| 3923 | int gpos; |
| 3924 | int hpos; |
| 3925 | int score; |
| 3926 | int k, l; |
| 3927 | |
| 3928 | /* Search for the right orientation. */ |
| 3929 | for (k = 0; k < 4; k++) { |
| 3930 | int up = delta[k]; |
| 3931 | if (ON_BOARD(apos - up)) |
| 3932 | continue; |
| 3933 | if (board[apos + up] != color || !same_string(apos + up, str)) |
| 3934 | return; |
| 3935 | |
| 3936 | for (l = 0; l < 2; l++) { |
| 3937 | int right = delta[(k+1)%4]; |
| 3938 | if (l == 1) |
| 3939 | right = -right; |
| 3940 | |
| 3941 | cpos = apos + right; |
| 3942 | dpos = apos + right + up; |
| 3943 | |
| 3944 | if (board[cpos] != color || board[dpos] != other) |
| 3945 | continue; |
| 3946 | |
| 3947 | epos = cpos + right; |
| 3948 | fpos = dpos + right; |
| 3949 | gpos = epos + right; |
| 3950 | hpos = apos - right; |
| 3951 | |
| 3952 | if (!ON_BOARD(epos)) |
| 3953 | continue; |
| 3954 | |
| 3955 | if (board[epos] == EMPTY && board[fpos] == EMPTY |
| 3956 | && (board[gpos] != color)) { |
| 3957 | /* Everything is set up, suggest moves at e and f. */ |
| 3958 | if (!ON_BOARD(hpos) || board[hpos] == color) |
| 3959 | score = 0; |
| 3960 | else |
| 3961 | score = -5; |
| 3962 | if (countlib(str) == 2) |
| 3963 | score -= 10; |
| 3964 | ADD_CANDIDATE_MOVE(epos, score, *moves, "edge_block-A"); |
| 3965 | |
| 3966 | if (countlib(dpos) == 1) |
| 3967 | score = 25; |
| 3968 | else |
| 3969 | score = 0; |
| 3970 | if (countlib(str) == 2) |
| 3971 | score -= 10; |
| 3972 | ADD_CANDIDATE_MOVE(fpos, score, *moves, "edge_block-B"); |
| 3973 | } |
| 3974 | else if (countlib(cpos) == 2 && countlib(dpos) > 1) { |
| 3975 | int libs[2]; |
| 3976 | int move; |
| 3977 | findlib(cpos, 2, libs); |
| 3978 | if (libs[0] == apos) |
| 3979 | move = libs[1]; |
| 3980 | else |
| 3981 | move = libs[0]; |
| 3982 | if (!is_self_atari(move, other)) |
| 3983 | ADD_CANDIDATE_MOVE(move, 0, *moves, "edge_block-C"); |
| 3984 | } |
| 3985 | } |
| 3986 | } |
| 3987 | } |
| 3988 | |
| 3989 | #else |
| 3990 | |
| 3991 | /* In positions like |
| 3992 | * |
| 3993 | * OOX.. |
| 3994 | * XXO*. |
| 3995 | * x.X.. |
| 3996 | * ----- |
| 3997 | * |
| 3998 | * where the X stones to the left are being attacked, it is usually |
| 3999 | * important to start by considering the move at *. Thus we propose |
| 4000 | * the move at * with a high initial score. |
| 4001 | * |
| 4002 | * Also, it is often needed to prevent "crawling" along first line |
| 4003 | * which can eventually give defender more liberties, like here: |
| 4004 | * |
| 4005 | * O.OO..X |
| 4006 | * OXXO..X |
| 4007 | * ...X*.. |
| 4008 | * ------- |
| 4009 | * |
| 4010 | * This function identifies the situation |
| 4011 | * |
| 4012 | * XO.? bdf? |
| 4013 | * .X.o aceg |
| 4014 | * ---- ---- |
| 4015 | * |
| 4016 | * where a is a liberty of the attacked string, b is a stone of the |
| 4017 | * attacked string, and e and f are the considered moves. |
| 4018 | */ |
| 4019 | |
| 4020 | static void |
| 4021 | edge_block_moves(int str, int apos, struct reading_moves *moves) |
| 4022 | { |
| 4023 | int color = board[str]; |
| 4024 | int other = OTHER_COLOR(color); |
| 4025 | int k; |
| 4026 | |
| 4027 | /* Search for the right orientation. */ |
| 4028 | for (k = 0; k < 4; k++) { |
| 4029 | int l; |
| 4030 | int up = delta[k]; |
| 4031 | |
| 4032 | if (ON_BOARD(apos - up)) |
| 4033 | continue; |
| 4034 | if (board[apos + up] != color || !same_string(apos + up, str)) |
| 4035 | return; |
| 4036 | |
| 4037 | for (l = 0; l < 2; l++) { |
| 4038 | int right = delta[(k+1)%4]; |
| 4039 | int cpos; |
| 4040 | int dpos; |
| 4041 | int epos; |
| 4042 | int fpos; |
| 4043 | |
| 4044 | if (l == 1) |
| 4045 | right = -right; |
| 4046 | |
| 4047 | cpos = apos + right; |
| 4048 | dpos = apos + right + up; |
| 4049 | epos = cpos + right; |
| 4050 | fpos = dpos + right; |
| 4051 | |
| 4052 | if (board[cpos] == color && board[dpos] == other |
| 4053 | && board[epos] == EMPTY && board[fpos] == EMPTY) { |
| 4054 | if (countlib(dpos) == 1) { |
| 4055 | int gpos = epos + right; |
| 4056 | |
| 4057 | /* Check if we have the first situation. */ |
| 4058 | if (board[gpos] != color) |
| 4059 | ADD_CANDIDATE_MOVE(fpos, 30, *moves, "edge_block-A"); |
| 4060 | } |
| 4061 | else { |
| 4062 | int edge_scan; |
| 4063 | |
| 4064 | /* Look along board edge to see if the defender's string can |
| 4065 | * run away to a friend. |
| 4066 | */ |
| 4067 | for (edge_scan = epos; ; edge_scan += right) { |
| 4068 | if (board[edge_scan] == color || board[edge_scan + up] == color) { |
| 4069 | ADD_CANDIDATE_MOVE(epos, 10, *moves, "edge_block-B"); |
| 4070 | break; |
| 4071 | } |
| 4072 | |
| 4073 | if (board[edge_scan] != EMPTY || board[edge_scan + up] != EMPTY) |
| 4074 | break; |
| 4075 | } |
| 4076 | } |
| 4077 | } |
| 4078 | } |
| 4079 | } |
| 4080 | } |
| 4081 | |
| 4082 | #endif |
| 4083 | |
| 4084 | /* ================================================================ */ |
| 4085 | /* Defending by attacking surrounding strings */ |
| 4086 | /* ================================================================ */ |
| 4087 | |
| 4088 | /* Add the chainbreaking moves relative to the string (str) to the |
| 4089 | * (moves) struct. |
| 4090 | */ |
| 4091 | static void |
| 4092 | break_chain_moves(int str, struct reading_moves *moves) |
| 4093 | { |
| 4094 | int r; |
| 4095 | int xpos; |
| 4096 | int adj, adjs[MAXCHAIN]; |
| 4097 | |
| 4098 | /* Find links in atari. */ |
| 4099 | adj = chainlinks2(str, adjs, 1); |
| 4100 | |
| 4101 | for (r = 0; r < adj; r++) { |
| 4102 | findlib(adjs[r], 1, &xpos); |
| 4103 | ADD_CANDIDATE_MOVE(xpos, 1, *moves, "break_chain"); |
| 4104 | } |
| 4105 | } |
| 4106 | |
| 4107 | |
| 4108 | /* defend_secondary_chain1_moves() tries to break a chain by defending |
| 4109 | * "secondary chain", that is, own strings surrounding a given |
| 4110 | * opponent string (which is in turn a chainlink for another own |
| 4111 | * string, phew... :). It only defends own strings in atari. |
| 4112 | * |
| 4113 | * When defending is done by stretching, it is required that the defending |
| 4114 | * stone played gets at least `min_liberties', or one less if it is |
| 4115 | * adjacent to the opponent chainlink. |
| 4116 | * |
| 4117 | * Returns true if there where any secondary strings that needed defence |
| 4118 | * (which does not imply they actually where defended). |
| 4119 | */ |
| 4120 | static int |
| 4121 | defend_secondary_chain1_moves(int str, struct reading_moves *moves, |
| 4122 | int min_liberties) |
| 4123 | { |
| 4124 | int r, s; |
| 4125 | int color = OTHER_COLOR(board[str]); |
| 4126 | int xpos; |
| 4127 | int adj; |
| 4128 | int adj2; |
| 4129 | int adjs[MAXCHAIN]; |
| 4130 | int adjs2[MAXCHAIN]; |
| 4131 | |
| 4132 | /* Find links in atari. */ |
| 4133 | adj = chainlinks2(str, adjs, 1); |
| 4134 | |
| 4135 | for (r = 0; r < adj; r++) { |
| 4136 | /* Stretch out. */ |
| 4137 | findlib(adjs[r], 1, &xpos); |
| 4138 | if (approxlib(xpos, color, min_liberties, NULL) |
| 4139 | + neighbor_of_string(xpos, str) >= min_liberties) |
| 4140 | ADD_CANDIDATE_MOVE(xpos, 0, *moves, "defend_secondary_chain1-A"); |
| 4141 | |
| 4142 | /* Capture adjacent stones in atari, if any. */ |
| 4143 | adj2 = chainlinks2(adjs[r], adjs2, 1); |
| 4144 | for (s = 0; s < adj2; s++) { |
| 4145 | findlib(adjs2[s], 1, &xpos); |
| 4146 | if (!is_self_atari(xpos, color)) |
| 4147 | ADD_CANDIDATE_MOVE(xpos, 0, *moves, "defend_secondary_chain1-B"); |
| 4148 | } |
| 4149 | } |
| 4150 | |
| 4151 | return adj; |
| 4152 | } |
| 4153 | |
| 4154 | |
| 4155 | /* defend_secondary_chain2_moves() tries to break a chain by defending |
| 4156 | * "secondary chain", that is, own strings surrounding a given |
| 4157 | * opponent string (which is in turn a chainlink for another own |
| 4158 | * string, phew... :). It only defends own strings in |
| 4159 | * with two liberties. |
| 4160 | * |
| 4161 | * When defending is done by stretching, it is required that the defending |
| 4162 | * stone played gets at least `min_liberties', or one less if it is |
| 4163 | * adjacent to the opponent chainlink. Defence can also be done by capturing |
| 4164 | * opponent stones or trying to capture them with an atari. |
| 4165 | */ |
| 4166 | static void |
| 4167 | defend_secondary_chain2_moves(int str, struct reading_moves *moves, |
| 4168 | int min_liberties) |
| 4169 | { |
| 4170 | int r, s, t; |
| 4171 | int color = OTHER_COLOR(board[str]); |
| 4172 | int xpos; |
| 4173 | int adj; |
| 4174 | int adj2; |
| 4175 | int adjs[MAXCHAIN]; |
| 4176 | int adjs2[MAXCHAIN]; |
| 4177 | int libs[2]; |
| 4178 | |
| 4179 | /* Find links with two liberties. */ |
| 4180 | adj = chainlinks2(str, adjs, 2); |
| 4181 | |
| 4182 | for (r = 0; r < adj; r++) { |
| 4183 | if (!have_common_lib(str, adjs[r], NULL)) |
| 4184 | continue; |
| 4185 | |
| 4186 | /* Stretch out. */ |
| 4187 | findlib(adjs[r], 2, libs); |
| 4188 | for (t = 0; t < 2; t++) { |
| 4189 | xpos = libs[t]; |
| 4190 | if (approxlib(xpos, color, min_liberties, NULL) |
| 4191 | + neighbor_of_string(xpos, str) >= min_liberties) |
| 4192 | ADD_CANDIDATE_MOVE(xpos, 0, *moves, "defend_secondary_chain2-A"); |
| 4193 | } |
| 4194 | |
| 4195 | /* Capture adjacent stones in atari, if any. */ |
| 4196 | adj2 = chainlinks2(adjs[r], adjs2, 1); |
| 4197 | for (s = 0; s < adj2; s++) { |
| 4198 | findlib(adjs2[s], 1, &xpos); |
| 4199 | if (!is_self_atari(xpos, color)) |
| 4200 | ADD_CANDIDATE_MOVE(xpos, 0, *moves, "defend_secondary_chain2-B"); |
| 4201 | } |
| 4202 | |
| 4203 | /* Look for neighbours we can atari. */ |
| 4204 | adj2 = chainlinks2(adjs[r], adjs2, 2); |
| 4205 | for (s = 0; s < adj2; s++) { |
| 4206 | findlib(adjs2[s], 2, libs); |
| 4207 | for (t = 0; t < 2; t++) { |
| 4208 | /* Only atari if target has no easy escape with his other liberty. */ |
| 4209 | if (approxlib(libs[1-t], OTHER_COLOR(color), 3, NULL) < 3 |
| 4210 | && !is_self_atari(libs[t], color)) { |
| 4211 | ADD_CANDIDATE_MOVE(libs[t], 0, *moves, "defend_secondary_chain2-C"); |
| 4212 | } |
| 4213 | } |
| 4214 | } |
| 4215 | } |
| 4216 | } |
| 4217 | |
| 4218 | |
| 4219 | /* |
| 4220 | * Find moves which immediately capture chain links with 2 |
| 4221 | * liberties, in the sense that the links cannot escape atari. |
| 4222 | * |
| 4223 | * The used heuristics are slightly sloppy, so useless moves may |
| 4224 | * appear occasionally. This should, however, only lead to slightly |
| 4225 | * worse performance but not to incorrect results. |
| 4226 | */ |
| 4227 | static void |
| 4228 | break_chain2_efficient_moves(int str, struct reading_moves *moves) |
| 4229 | { |
| 4230 | int r; |
| 4231 | int adj, adjs[MAXCHAIN]; |
| 4232 | |
| 4233 | /* Find links with 2 liberties. */ |
| 4234 | adj = chainlinks2(str, adjs, 2); |
| 4235 | |
| 4236 | for (r = 0; r < adj; r++) |
| 4237 | do_find_break_chain2_efficient_moves(str, adjs[r], moves); |
| 4238 | } |
| 4239 | |
| 4240 | |
| 4241 | /* Helper function for break_chain2_efficient_moves(). */ |
| 4242 | static void |
| 4243 | do_find_break_chain2_efficient_moves(int str, int adj, |
| 4244 | struct reading_moves *moves) |
| 4245 | { |
| 4246 | int color = board[str]; |
| 4247 | int other = OTHER_COLOR(color); |
| 4248 | int k; |
| 4249 | int adj2, adjs2[MAXCHAIN]; |
| 4250 | int libs[2]; |
| 4251 | int pos1; |
| 4252 | int pos2; |
| 4253 | ASSERT1(countlib(adj) == 2, adj); |
| 4254 | |
| 4255 | adj2 = chainlinks2(adj, adjs2, 1); |
| 4256 | if (adj2 == 1 && countlib(str) > 2) { |
| 4257 | int apos; |
| 4258 | break_chain_moves(adjs2[0], moves); |
| 4259 | findlib(adjs2[0], 1, &apos); |
| 4260 | if (!is_self_atari(apos, color)) |
| 4261 | ADD_CANDIDATE_MOVE(apos, 0, *moves, "break_chain2_efficient-A"); |
| 4262 | return; |
| 4263 | } |
| 4264 | |
| 4265 | if (adj2 > 1) |
| 4266 | return; |
| 4267 | |
| 4268 | findlib(adj, 2, libs); |
| 4269 | for (k = 0; k < 2; k++) |
| 4270 | if (approxlib(libs[k], other, 3, NULL) <= 2 |
| 4271 | && !is_self_atari(libs[1 - k], color)) |
| 4272 | ADD_CANDIDATE_MOVE(libs[1 - k], 0, *moves, "break_chain2_efficient-B"); |
| 4273 | |
| 4274 | /* A common special case is this kind of edge position |
| 4275 | * |
| 4276 | * ..XXX. |
| 4277 | * X.XOO. |
| 4278 | * XOOX*. |
| 4279 | * ...... |
| 4280 | * ------ |
| 4281 | * |
| 4282 | * where a move at * is most effective for saving the two stones |
| 4283 | * to the left. |
| 4284 | * |
| 4285 | * The code below tries to identify this case. We use the crude |
| 4286 | * heuristic that the two liberties of the X stone we want to |
| 4287 | * capture should be placed diagonally and that one liberty should |
| 4288 | * be on the edge. Then we propose to play the other liberty. |
| 4289 | * Notice that both moves may be proposed when attacking a stone |
| 4290 | * on 2-2. |
| 4291 | * |
| 4292 | * Update: This was too crude. Also require that the X stone is on |
| 4293 | * the second line and that the proposed move is not a self-atari. |
| 4294 | */ |
| 4295 | if (!DIAGONAL_NEIGHBORS(libs[0], libs[1])) |
| 4296 | return; |
| 4297 | |
| 4298 | /* Since we know that the two liberties are diagonal, the following |
| 4299 | * construction gives the two vertices "between" the liberties. |
| 4300 | */ |
| 4301 | pos1 = NORTH(gg_max(libs[0], libs[1])); |
| 4302 | pos2 = SOUTH(gg_min(libs[0], libs[1])); |
| 4303 | if ((board[pos1] != other |
| 4304 | || !is_edge_vertex(pos2) |
| 4305 | || !same_string(pos1, adj)) |
| 4306 | && (board[pos2] != other |
| 4307 | || !is_edge_vertex(pos1) |
| 4308 | || !same_string(pos2, adj))) |
| 4309 | return; |
| 4310 | |
| 4311 | if (is_edge_vertex(libs[0]) && !is_self_atari(libs[1], color)) |
| 4312 | ADD_CANDIDATE_MOVE(libs[1], 1, *moves, "break_chain2_efficient-C"); |
| 4313 | |
| 4314 | if (is_edge_vertex(libs[1]) && !is_self_atari(libs[0], color)) |
| 4315 | ADD_CANDIDATE_MOVE(libs[0], 1, *moves, "break_chain2_efficient-C"); |
| 4316 | } |
| 4317 | |
| 4318 | |
| 4319 | /* (str) points to a string with two or more liberties. break_chain2_moves() |
| 4320 | * tries to defend this string by attacking a neighbouring string with |
| 4321 | * two liberties. |
| 4322 | * This is done by playing on either of its liberties |
| 4323 | * (if (require_safe) is true these are only used if they are not |
| 4324 | * self-ataris), taking a neighbour out of atari or by backfilling if |
| 4325 | * both liberties are self-ataris. |
| 4326 | */ |
| 4327 | static void |
| 4328 | break_chain2_moves(int str, struct reading_moves *moves, int require_safe, |
| 4329 | int be_aggressive) |
| 4330 | { |
| 4331 | int color = board[str]; |
| 4332 | int other = OTHER_COLOR(color); |
| 4333 | int r; |
| 4334 | int adj; |
| 4335 | int adjs[MAXCHAIN]; |
| 4336 | |
| 4337 | adj = chainlinks2(str, adjs, 2); |
| 4338 | |
| 4339 | for (r = 0; r < adj; r++) { |
| 4340 | int k; |
| 4341 | int apos = adjs[r]; |
| 4342 | int libs[2]; |
| 4343 | int unsafe[2]; |
| 4344 | int dummy_adjs[MAXCHAIN]; |
| 4345 | |
| 4346 | findlib(apos, 2, libs); |
| 4347 | |
| 4348 | /* If stackp > backfill_depth, don't bother playing liberties of |
| 4349 | * 2-liberty strings if those also have at least one neighbor in |
| 4350 | * atari. This is intended to solve reading:171 and generally reduce |
| 4351 | * the number of nodes. |
| 4352 | */ |
| 4353 | if (stackp > backfill_depth |
| 4354 | && chainlinks2(apos, dummy_adjs, 1) > 0) |
| 4355 | continue; |
| 4356 | |
| 4357 | for (k = 0; k < 2; k++) { |
| 4358 | unsafe[k] = is_self_atari(libs[k], color); |
| 4359 | if (!unsafe[k] |
| 4360 | || is_ko(libs[k], color, NULL) |
| 4361 | || (!require_safe |
| 4362 | && approxlib(libs[k], other, 5, NULL) < 5)) |
| 4363 | ADD_CANDIDATE_MOVE(libs[k], 0, *moves, "break_chain2-A"); |
| 4364 | } |
| 4365 | |
| 4366 | if (stackp <= break_chain_depth |
| 4367 | || (be_aggressive && stackp <= backfill_depth)) { |
| 4368 | /* If the chain link cannot escape easily, try to defend all adjacent |
| 4369 | * friendly stones in atari (if any). If there are none, defend |
| 4370 | * adjacent friendly stones with only two liberties. |
| 4371 | */ |
| 4372 | if (approxlib(libs[0], other, 4, NULL) < 4 |
| 4373 | && approxlib(libs[1], other, 4, NULL) < 4) { |
| 4374 | if (!defend_secondary_chain1_moves(adjs[r], moves, 2)) |
| 4375 | defend_secondary_chain2_moves(adjs[r], moves, 2); |
| 4376 | } |
| 4377 | } |
| 4378 | |
| 4379 | if (unsafe[0] && unsafe[1] |
| 4380 | && (stackp <= backfill2_depth || have_common_lib(str, apos, NULL))) { |
| 4381 | int lib; |
| 4382 | |
| 4383 | /* Find backfilling moves. */ |
| 4384 | for (k = 0; k < 2; k++) { |
| 4385 | int libs2[3]; |
| 4386 | if (approxlib(libs[k], other, 3, libs2) == 2) { |
| 4387 | if (!is_self_atari(libs2[0], color)) |
| 4388 | ADD_CANDIDATE_MOVE(libs2[0], 0, *moves, "break_chain2-B"); |
| 4389 | if (!is_self_atari(libs2[1], color)) |
| 4390 | ADD_CANDIDATE_MOVE(libs2[1], 0, *moves, "break_chain2-B"); |
| 4391 | } |
| 4392 | } |
| 4393 | |
| 4394 | /* Consider this case (reading:188): |
| 4395 | * |
| 4396 | * |.OOOXXX |
| 4397 | * |OXXXOOO |
| 4398 | * |.X.O... |
| 4399 | * +------- |
| 4400 | * |
| 4401 | * We cannot atari the corner X string immediatly, so we need to |
| 4402 | * backfill. However, to avoid generating too many variations, |
| 4403 | * we require that the opponent string is well restrained. |
| 4404 | * Otherwise it could just run away while we backfill. |
| 4405 | */ |
| 4406 | if (approxlib(libs[0], other, 3, NULL) <= 2 |
| 4407 | && approxlib(libs[1], other, 3, NULL) <= 2) { |
| 4408 | if (approxlib(libs[0], color, 1, &lib) == 1 |
| 4409 | && approxlib(lib, color, 3, NULL) >= 3) |
| 4410 | ADD_CANDIDATE_MOVE(lib, 0, *moves, "break_chain2-C"); |
| 4411 | |
| 4412 | if (approxlib(libs[1], color, 1, &lib) == 1 |
| 4413 | && approxlib(lib, color, 3, NULL) >= 3) |
| 4414 | ADD_CANDIDATE_MOVE(lib, 0, *moves, "break_chain2-C"); |
| 4415 | } |
| 4416 | } |
| 4417 | } |
| 4418 | } |
| 4419 | |
| 4420 | /* |
| 4421 | * (str) points to a group to be defended. |
| 4422 | * break_chain2_defense_moves is a wrapper around break_chain2_moves. |
| 4423 | * It devalues all entries by 2. |
| 4424 | * |
| 4425 | * Rationale: Otherwise, these moves get overvalued by order_moves. In |
| 4426 | * particular, if there is both a direct and a break_chain2 defense, |
| 4427 | * then the latter one might be just an irrelevant intermediate forcing |
| 4428 | * move. Hence, we should rather return the direct defense. |
| 4429 | */ |
| 4430 | |
| 4431 | static void |
| 4432 | break_chain2_defense_moves(int str, struct reading_moves *moves, |
| 4433 | int be_aggressive) |
| 4434 | { |
| 4435 | int saved_num_moves = moves->num; |
| 4436 | int k; |
| 4437 | |
| 4438 | break_chain2_moves(str, moves, !(stackp <= backfill_depth), be_aggressive); |
| 4439 | for (k = saved_num_moves; k < moves->num; k++) |
| 4440 | moves->score[k] = -2; |
| 4441 | } |
| 4442 | |
| 4443 | |
| 4444 | /* Helper function for break_chain3_moves() and |
| 4445 | * superstring_break_chain_moves(). |
| 4446 | */ |
| 4447 | static void |
| 4448 | do_find_break_chain3_moves(int *chain_links, int num_chain_links, |
| 4449 | struct reading_moves *moves, int be_aggressive, |
| 4450 | const char *caller_function_name) |
| 4451 | { |
| 4452 | int other = board[chain_links[0]]; |
| 4453 | int color = OTHER_COLOR(other); |
| 4454 | signed char move_added[BOARDMAX]; |
| 4455 | int possible_moves[MAX_MOVES]; |
| 4456 | int num_possible_moves = 0; |
| 4457 | int r; |
| 4458 | int k; |
| 4459 | |
| 4460 | gg_assert(num_chain_links > 0); |
| 4461 | |
| 4462 | memset(move_added, 0, sizeof move_added); |
| 4463 | |
| 4464 | for (r = 0; r < num_chain_links; r++) { |
| 4465 | int lib1; |
| 4466 | int lib2; |
| 4467 | int lib3; |
| 4468 | int libs[3]; |
| 4469 | |
| 4470 | /* We make a list in the (adjs) array of the liberties |
| 4471 | * of boundary strings having exactly three liberties. We mark |
| 4472 | * each liberty in the mw array so that we do not list any |
| 4473 | * more than once. |
| 4474 | */ |
| 4475 | findlib(chain_links[r], 3, libs); |
| 4476 | |
| 4477 | /* If the 3 liberty chain easily can run away through one of the |
| 4478 | * liberties, we don't play on any of the other liberties. |
| 4479 | */ |
| 4480 | lib1 = approxlib(libs[0], other, 4, NULL); |
| 4481 | lib2 = approxlib(libs[1], other, 4, NULL); |
| 4482 | if (lib1 >= 4 && lib2 >= 4) |
| 4483 | continue; |
| 4484 | lib3 = approxlib(libs[2], other, 4, NULL); |
| 4485 | |
| 4486 | if ((lib1 >= 4 || lib2 >= 4) && lib3 >= 4) |
| 4487 | continue; |
| 4488 | |
| 4489 | if (lib1 >= 4) { |
| 4490 | if (!move_added[libs[0]]) { |
| 4491 | possible_moves[num_possible_moves++] = libs[0]; |
| 4492 | move_added[libs[0]] = 1; |
| 4493 | } |
| 4494 | |
| 4495 | continue; |
| 4496 | } |
| 4497 | |
| 4498 | if (lib2 >= 4) { |
| 4499 | if (!move_added[libs[1]]) { |
| 4500 | possible_moves[num_possible_moves++] = libs[1]; |
| 4501 | move_added[libs[1]] = 1; |
| 4502 | } |
| 4503 | |
| 4504 | continue; |
| 4505 | } |
| 4506 | |
| 4507 | if (lib3 >= 4) { |
| 4508 | if (!move_added[libs[2]]) { |
| 4509 | possible_moves[num_possible_moves++] = libs[2]; |
| 4510 | move_added[libs[2]] = 1; |
| 4511 | } |
| 4512 | |
| 4513 | continue; |
| 4514 | } |
| 4515 | |
| 4516 | /* No easy escape, try all liberties. */ |
| 4517 | for (k = 0; k < 3; k++) { |
| 4518 | if (!move_added[libs[k]]) { |
| 4519 | possible_moves[num_possible_moves++] = libs[k]; |
| 4520 | move_added[libs[k]] = 1; |
| 4521 | } |
| 4522 | } |
| 4523 | |
| 4524 | if (stackp <= backfill2_depth |
| 4525 | || (be_aggressive && stackp <= backfill_depth)) |
| 4526 | defend_secondary_chain1_moves(chain_links[r], moves, 3); |
| 4527 | } |
| 4528 | |
| 4529 | for (k = 0; k < num_possible_moves; k++) { |
| 4530 | /* We do not wish to consider the move if it can be immediately |
| 4531 | * recaptured, unless stackp < backfill2_depth. Beyond |
| 4532 | * backfill2_depth, the necessary capturing move might not get |
| 4533 | * generated in follow-up for the attacker. (This currently only |
| 4534 | * makes a difference at stackp == backfill2_depth.) |
| 4535 | */ |
| 4536 | int move = possible_moves[k]; |
| 4537 | |
| 4538 | if (stackp <= break_chain_depth |
| 4539 | || (be_aggressive && stackp <= backfill_depth) |
| 4540 | || approxlib(move, color, 2, NULL) > 1) |
| 4541 | /* We use a negative initial score here as we prefer to find |
| 4542 | * direct defense moves. |
| 4543 | */ |
| 4544 | ADD_CANDIDATE_MOVE(move, -2, *moves, caller_function_name); |
| 4545 | } |
| 4546 | } |
| 4547 | |
| 4548 | |
| 4549 | /* |
| 4550 | * (str) points to a group. |
| 4551 | * If there is a string in the surrounding chain having |
| 4552 | * exactly three liberties whose attack leads to the rescue of |
| 4553 | * (str), break_chain3_moves(str, *moves) adds attack moves against |
| 4554 | * the surrounding string as candidate moves. |
| 4555 | */ |
| 4556 | |
| 4557 | static void |
| 4558 | break_chain3_moves(int str, struct reading_moves *moves, int be_aggressive) |
| 4559 | { |
| 4560 | int chain_links[MAXCHAIN]; |
| 4561 | int num_chain_links = chainlinks2(str, chain_links, 3); |
| 4562 | |
| 4563 | if (num_chain_links > 0) { |
| 4564 | do_find_break_chain3_moves(chain_links, num_chain_links, |
| 4565 | moves, be_aggressive, "break_chain3"); |
| 4566 | } |
| 4567 | } |
| 4568 | |
| 4569 | |
| 4570 | /* |
| 4571 | * (str) points to a group. |
| 4572 | * If there is a string in the surrounding chain having |
| 4573 | * exactly four liberties whose attack leads to the rescue of |
| 4574 | * (str), break_chain4_moves(str, *moves) adds attack moves against |
| 4575 | * the surrounding string as candidate moves. |
| 4576 | */ |
| 4577 | |
| 4578 | static void |
| 4579 | break_chain4_moves(int str, struct reading_moves *moves, int be_aggressive) |
| 4580 | { |
| 4581 | int color = board[str]; |
| 4582 | int other = OTHER_COLOR(color); |
| 4583 | int r; |
| 4584 | int k; |
| 4585 | int u = 0, v; |
| 4586 | int apos; |
| 4587 | int adj; |
| 4588 | int adjs[MAXCHAIN]; |
| 4589 | int libs[4]; |
| 4590 | int possible_moves[MAX_MOVES]; |
| 4591 | int mw[BOARDMAX]; |
| 4592 | |
| 4593 | memset(mw, 0, sizeof(mw)); |
| 4594 | |
| 4595 | adj = chainlinks2(str, adjs, 4); |
| 4596 | for (r = 0; r < adj; r++) { |
| 4597 | int lib1 = 0, lib2 = 0, lib3 = 0, lib4 = 0; |
| 4598 | apos = adjs[r]; |
| 4599 | |
| 4600 | /* We make a list in the (adjs) array of the liberties |
| 4601 | * of boundary strings having exactly four liberties. We mark |
| 4602 | * each liberty in the mw array so that we do not list any |
| 4603 | * more than once. |
| 4604 | */ |
| 4605 | findlib(apos, 4, libs); |
| 4606 | |
| 4607 | /* If the 4 liberty chain easily can run away through one of the |
| 4608 | * liberties, we don't play on any of the other liberties. |
| 4609 | */ |
| 4610 | lib1 = approxlib(libs[0], other, 5, NULL); |
| 4611 | lib2 = approxlib(libs[1], other, 5, NULL); |
| 4612 | if (lib1 >= 5 && lib2 >= 5) |
| 4613 | continue; |
| 4614 | lib3 = approxlib(libs[2], other, 5, NULL); |
| 4615 | |
| 4616 | if ((lib1 >= 5 || lib2 >= 5) && lib3 >= 5) |
| 4617 | continue; |
| 4618 | lib4 = approxlib(libs[3], other, 5, NULL); |
| 4619 | |
| 4620 | if ((lib1 >= 5 || lib2 >= 5 || lib3 >= 5) && lib4 >= 5) |
| 4621 | continue; |
| 4622 | |
| 4623 | if (lib1 >= 5 && !mw[libs[0]]) { |
| 4624 | mw[libs[0]] = 1; |
| 4625 | possible_moves[u++] = libs[0]; |
| 4626 | continue; |
| 4627 | } |
| 4628 | |
| 4629 | if (lib2 >= 5 && !mw[libs[1]]) { |
| 4630 | mw[libs[1]] = 1; |
| 4631 | possible_moves[u++] = libs[1]; |
| 4632 | continue; |
| 4633 | } |
| 4634 | |
| 4635 | if (lib3 >= 5 && !mw[libs[2]]) { |
| 4636 | mw[libs[2]] = 1; |
| 4637 | possible_moves[u++] = libs[2]; |
| 4638 | continue; |
| 4639 | } |
| 4640 | |
| 4641 | if (lib4 >= 5 && !mw[libs[3]]) { |
| 4642 | mw[libs[3]] = 1; |
| 4643 | possible_moves[u++] = libs[3]; |
| 4644 | continue; |
| 4645 | } |
| 4646 | |
| 4647 | /* No easy escape, try all liberties. */ |
| 4648 | for (k = 0; k < 4; k++) { |
| 4649 | if (!mw[libs[k]]) { |
| 4650 | mw[libs[k]] = 1; |
| 4651 | possible_moves[u++] = libs[k]; |
| 4652 | } |
| 4653 | } |
| 4654 | |
| 4655 | if (stackp <= backfill2_depth |
| 4656 | || (be_aggressive && stackp <= backfill_depth)) |
| 4657 | defend_secondary_chain1_moves(adjs[r], moves, 4); |
| 4658 | } |
| 4659 | |
| 4660 | for (v = 0; v < u; v++) { |
| 4661 | /* We do not wish to consider the move if it can be |
| 4662 | * immediately recaptured, unless stackp < backfill2_depth. |
| 4663 | * Beyond backfill2_depth, the necessary capturing move might not |
| 4664 | * get generated in follow-up for the attacker. |
| 4665 | * (This currently only makes a difference at stackp == backfill2_depth.) |
| 4666 | */ |
| 4667 | int xpos = possible_moves[v]; |
| 4668 | if (stackp <= break_chain_depth |
| 4669 | || (be_aggressive && stackp <= backfill_depth) |
| 4670 | || approxlib(xpos, color, 2, NULL) > 1) |
| 4671 | /* We use a negative initial score here as we prefer to find |
| 4672 | * direct defense moves. |
| 4673 | */ |
| 4674 | ADD_CANDIDATE_MOVE(xpos, -2, *moves, "break_chain4"); |
| 4675 | } |
| 4676 | } |
| 4677 | |
| 4678 | /* This function looks for moves attacking those components |
| 4679 | * of the surrounding chain of the superstring (see find_superstring |
| 4680 | * for the definition) which have fewer than liberty_cap liberties, |
| 4681 | * and which are not adjacent to the string itself, since those |
| 4682 | * are tested by break_chain_moves. |
| 4683 | */ |
| 4684 | static void |
| 4685 | superstring_break_chain_moves(int str, int liberty_cap, |
| 4686 | struct reading_moves *moves) |
| 4687 | { |
| 4688 | int adj; |
| 4689 | int adjs[MAXCHAIN]; |
| 4690 | int chain_links3[MAXCHAIN]; |
| 4691 | int num_chain_links3 = 0; |
| 4692 | int k; |
| 4693 | int apos; |
| 4694 | |
| 4695 | proper_superstring_chainlinks(str, &adj, adjs, liberty_cap); |
| 4696 | for (k = 0; k < adj; k++) { |
| 4697 | int liberties = countlib(adjs[k]); |
| 4698 | if (liberties == 1) { |
| 4699 | findlib(adjs[k], 1, &apos); |
| 4700 | ADD_CANDIDATE_MOVE(apos, 0, *moves, "superstring_break_chain"); |
| 4701 | } |
| 4702 | else if (liberties == 2) |
| 4703 | do_find_break_chain2_efficient_moves(str, adjs[k], moves); |
| 4704 | else if (liberties == 3) |
| 4705 | chain_links3[num_chain_links3++] = adjs[k]; |
| 4706 | } |
| 4707 | |
| 4708 | if (num_chain_links3 > 0) { |
| 4709 | do_find_break_chain3_moves(chain_links3, num_chain_links3, |
| 4710 | moves, 0, "superstring_break_chain-3"); |
| 4711 | } |
| 4712 | } |
| 4713 | |
| 4714 | /* |
| 4715 | * If `str' points to a group, double_atari_chain2_moves() adds all |
| 4716 | * moves which make a double atari on some strings in the surrounding |
| 4717 | * chain to the moves[] array. In addition, if `generate_more_moves' |
| 4718 | * is set, it adds moves that make atari on a string in the |
| 4719 | * surrounding chain and are adjacent to another string with 3 |
| 4720 | * liberties. |
| 4721 | */ |
| 4722 | |
| 4723 | static void |
| 4724 | double_atari_chain2_moves(int str, struct reading_moves *moves, |
| 4725 | int generate_more_moves) |
| 4726 | { |
| 4727 | int r, k; |
| 4728 | int adj; |
| 4729 | int adjs[MAXCHAIN]; |
| 4730 | int libs[3]; |
| 4731 | int mw[BOARDMAX]; |
| 4732 | |
| 4733 | memset(mw, 0, sizeof(mw)); |
| 4734 | |
| 4735 | adj = chainlinks2(str, adjs, 2); |
| 4736 | for (r = 0; r < adj; r++) { |
| 4737 | findlib(adjs[r], 2, libs); |
| 4738 | for (k = 0; k < 2; k++) { |
| 4739 | mw[libs[k]]++; |
| 4740 | if (mw[libs[k]] == 2) { |
| 4741 | /* Found a double atari, but don't play there unless the move |
| 4742 | * is safe for the defender. |
| 4743 | */ |
| 4744 | if (!is_self_atari(libs[k], board[str])) |
| 4745 | ADD_CANDIDATE_MOVE(libs[k], 1, *moves, "double_atari_chain2-A"); |
| 4746 | } |
| 4747 | } |
| 4748 | } |
| 4749 | |
| 4750 | if (generate_more_moves) { |
| 4751 | int adj3; |
| 4752 | int adjs3[MAXCHAIN]; |
| 4753 | |
| 4754 | adj3 = chainlinks2(str, adjs3, 3); |
| 4755 | for (r = 0; r < adj3; r++) { |
| 4756 | findlib(adjs3[r], 3, libs); |
| 4757 | for (k = 0; k < 3; k++) { |
| 4758 | if (mw[libs[k]] == 1) { |
| 4759 | mw[libs[k]] = 2; |
| 4760 | if (!is_self_atari(libs[k], board[str])) |
| 4761 | ADD_CANDIDATE_MOVE(libs[k], -3, *moves, "double_atari_chain2-B"); |
| 4762 | } |
| 4763 | } |
| 4764 | } |
| 4765 | } |
| 4766 | } |
| 4767 | |
| 4768 | |
| 4769 | /* ================================================================ */ |
| 4770 | /* Restricted Attack and Defense */ |
| 4771 | /* ================================================================ */ |
| 4772 | |
| 4773 | |
| 4774 | /* These functions try to attack and defend a string, avoiding moves |
| 4775 | * from a certain set. It is assumed that as soon as the string gets |
| 4776 | * three liberties, it is alive. |
| 4777 | * |
| 4778 | * These functions can be used to generate backfilling moves as |
| 4779 | * follows: Suppose that we would like to make atari on a |
| 4780 | * string, but the atari is not safe until we make a backfilling |
| 4781 | * move. To find the backfilling move, we make a list of the |
| 4782 | * liberties of the string under attack, declaring these moves |
| 4783 | * forbidden. Neither player will play them while the restricted |
| 4784 | * functions are in effect. We fill the liberty, creating a |
| 4785 | * string which is under attack, and look for a defensive move |
| 4786 | * which avoids the forbidden moves. This is the backfilling |
| 4787 | * move. |
| 4788 | * |
| 4789 | * These are minimalist functions capable of reading a ladder |
| 4790 | * and not much more. |
| 4791 | */ |
| 4792 | |
| 4793 | /* Given a list of moves, restricted_defend1 tries to find a |
| 4794 | * move that defends the string (str) with one liberty, |
| 4795 | * not considering moves from the list. |
| 4796 | */ |
| 4797 | int |
| 4798 | restricted_defend1(int str, int *move, |
| 4799 | int num_forbidden_moves, int *forbidden_moves) |
| 4800 | { |
| 4801 | int color = board[str]; |
| 4802 | int other = OTHER_COLOR(color); |
| 4803 | int xpos; |
| 4804 | int lib; |
| 4805 | struct reading_moves moves; |
| 4806 | int savemove = 0; |
| 4807 | int savecode = 0; |
| 4808 | int liberties; |
| 4809 | int k; |
| 4810 | |
| 4811 | SETUP_TRACE_INFO("restricted_defend1", str); |
| 4812 | reading_node_counter++; |
| 4813 | moves.num = 0; |
| 4814 | |
| 4815 | ASSERT1(IS_STONE(board[str]), str); |
| 4816 | ASSERT1(countlib(str) == 1, str); |
| 4817 | |
| 4818 | /* (lib) will be the liberty of the string. */ |
| 4819 | liberties = findlib(str, 1, &lib); |
| 4820 | ASSERT1(liberties == 1, str); |
| 4821 | |
| 4822 | /* Collect moves to try in the first batch. |
| 4823 | * 1. First order liberty. |
| 4824 | * 2. Chain breaking moves. |
| 4825 | * 3. Moves to set up a snapback. |
| 4826 | */ |
| 4827 | moves.pos[0] = lib; |
| 4828 | moves.score[0] = 0; |
| 4829 | moves.message[0] = "liberty"; |
| 4830 | moves.num = 1; |
| 4831 | moves.num_tried = 0; |
| 4832 | |
| 4833 | break_chain_moves(str, &moves); |
| 4834 | set_up_snapback_moves(str, lib, &moves); |
| 4835 | order_moves(str, &moves, color, read_function_name, NO_MOVE); |
| 4836 | |
| 4837 | for (k = 0; k < moves.num; k++) { |
| 4838 | int ko_capture; |
| 4839 | |
| 4840 | xpos = moves.pos[k]; |
| 4841 | if (in_list(xpos, num_forbidden_moves, forbidden_moves)) |
| 4842 | continue; |
| 4843 | /* To avoid loops with double ko, we do not allow any ko captures, |
| 4844 | * even legal ones, if the opponent is komaster. |
| 4845 | */ |
| 4846 | if (is_ko(xpos, color, NULL)) |
| 4847 | ko_capture = 1; |
| 4848 | else |
| 4849 | ko_capture = 0; |
| 4850 | |
| 4851 | if ((get_komaster() != other || !ko_capture) |
| 4852 | && trymove(xpos, color, moves.message[k], str)) { |
| 4853 | int libs = countlib(str); |
| 4854 | if (libs > 2) { |
| 4855 | popgo(); |
| 4856 | SGFTRACE(xpos, WIN, "defense effective"); |
| 4857 | if (move) |
| 4858 | *move = xpos; |
| 4859 | return WIN; |
| 4860 | } |
| 4861 | if (libs == 2) { |
| 4862 | int acode; |
| 4863 | |
| 4864 | if (!ko_capture) |
| 4865 | acode = restricted_attack2(str, NULL, |
| 4866 | num_forbidden_moves, forbidden_moves); |
| 4867 | else |
| 4868 | acode = restricted_attack2(str, NULL, |
| 4869 | num_forbidden_moves, forbidden_moves); |
| 4870 | popgo(); |
| 4871 | if (acode == 0) { |
| 4872 | SGFTRACE(xpos, WIN, "defense effective"); |
| 4873 | if (move) |
| 4874 | *move = xpos; |
| 4875 | return WIN; |
| 4876 | } |
| 4877 | /* if the move works with ko we save it, then look for something |
| 4878 | * better. |
| 4879 | */ |
| 4880 | UPDATE_SAVED_KO_RESULT(savecode, savemove, acode, xpos); |
| 4881 | } |
| 4882 | else |
| 4883 | popgo(); |
| 4884 | } |
| 4885 | else { |
| 4886 | int ko_pos; |
| 4887 | if (stackp <= ko_depth |
| 4888 | && savecode == 0 |
| 4889 | && (get_komaster() == EMPTY |
| 4890 | || (get_komaster() == color |
| 4891 | && get_kom_pos() == xpos)) |
| 4892 | && is_ko(xpos, color, &ko_pos) |
| 4893 | && tryko(xpos, color, "restricted_defend1-B")) { |
| 4894 | int libs = countlib(str); |
| 4895 | if (libs > 2) { |
| 4896 | popgo(); |
| 4897 | UPDATE_SAVED_KO_RESULT(savecode, savemove, 2, xpos); |
| 4898 | } |
| 4899 | else if (libs == 2) { |
| 4900 | int acode; |
| 4901 | acode = restricted_attack2(str, NULL, |
| 4902 | num_forbidden_moves, forbidden_moves); |
| 4903 | popgo(); |
| 4904 | UPDATE_SAVED_KO_RESULT(savecode, savemove, acode, xpos); |
| 4905 | } |
| 4906 | else |
| 4907 | popgo(); |
| 4908 | } |
| 4909 | } |
| 4910 | } |
| 4911 | |
| 4912 | if (savecode != 0) { |
| 4913 | if (move) |
| 4914 | *move = savemove; |
| 4915 | SGFTRACE(savemove, savecode, "saved move"); |
| 4916 | return savecode; |
| 4917 | } |
| 4918 | |
| 4919 | SGFTRACE(0, 0, NULL); |
| 4920 | return 0; |
| 4921 | } |
| 4922 | |
| 4923 | |
| 4924 | /* Given a list of moves, restricted_attack2 tries to find a |
| 4925 | * move that attacks the string (str) with two liberties, |
| 4926 | * not considering moves from the list. |
| 4927 | */ |
| 4928 | int |
| 4929 | restricted_attack2(int str, int *move, |
| 4930 | int num_forbidden_moves, int *forbidden_moves) |
| 4931 | { |
| 4932 | int color = board[str]; |
| 4933 | int other = OTHER_COLOR(color); |
| 4934 | int apos; |
| 4935 | int liberties; |
| 4936 | int libs[2]; |
| 4937 | int savemove = 0; |
| 4938 | int savecode = 0; |
| 4939 | int k; |
| 4940 | |
| 4941 | SETUP_TRACE_INFO("restricted_attack2", str); |
| 4942 | reading_node_counter++; |
| 4943 | |
| 4944 | str = find_origin(str); |
| 4945 | ASSERT1(IS_STONE(board[str]), str); |
| 4946 | ASSERT1(countlib(str) == 2, str); |
| 4947 | |
| 4948 | /* The attack may fail if a boundary string is in atari and cannot |
| 4949 | * be defended. First we must try defending such a string. |
| 4950 | */ |
| 4951 | /* Get the two liberties of (str). */ |
| 4952 | liberties = findlib(str, 2, libs); |
| 4953 | ASSERT1(liberties == 2, str); |
| 4954 | |
| 4955 | for (k = 0; k < 2; k++) { |
| 4956 | int ko_pos; |
| 4957 | int ko_capture; |
| 4958 | |
| 4959 | apos = libs[k]; |
| 4960 | if (in_list(apos, num_forbidden_moves, forbidden_moves)) |
| 4961 | continue; |
| 4962 | /* To avoid loops with double ko, we do not allow any ko captures, |
| 4963 | * even legal ones, if the opponent is komaster. |
| 4964 | */ |
| 4965 | if (is_ko(apos, other, &ko_pos)) |
| 4966 | ko_capture = 1; |
| 4967 | else |
| 4968 | ko_capture = 0; |
| 4969 | |
| 4970 | if ((get_komaster() != color || !ko_capture) |
| 4971 | && trymove(apos, other, "restricted_attack2", str)) { |
| 4972 | if ((!ko_capture |
| 4973 | && !restricted_defend1(str, NULL, |
| 4974 | num_forbidden_moves, forbidden_moves)) |
| 4975 | || (ko_capture |
| 4976 | && !restricted_defend1(str, NULL, |
| 4977 | num_forbidden_moves, forbidden_moves))) { |
| 4978 | popgo(); |
| 4979 | SGFTRACE(apos, WIN, "attack effective"); |
| 4980 | if (move) |
| 4981 | *move = apos; |
| 4982 | return WIN; |
| 4983 | } |
| 4984 | popgo(); |
| 4985 | } |
| 4986 | else if (savecode == 0 |
| 4987 | && (get_komaster() == EMPTY |
| 4988 | || (get_komaster() == other |
| 4989 | && get_kom_pos() == apos)) |
| 4990 | && tryko(apos, other, "restricted_attack2")) { |
| 4991 | if (!restricted_defend1(str, NULL, |
| 4992 | num_forbidden_moves, forbidden_moves)) { |
| 4993 | popgo(); |
| 4994 | savecode = KO_B; |
| 4995 | savemove = apos; |
| 4996 | } |
| 4997 | else |
| 4998 | popgo(); |
| 4999 | } |
| 5000 | } |
| 5001 | |
| 5002 | if (savecode != 0) { |
| 5003 | if (move) |
| 5004 | *move = savemove; |
| 5005 | SGFTRACE(savemove, savecode, "saved move"); |
| 5006 | return savecode; |
| 5007 | } |
| 5008 | |
| 5009 | SGFTRACE(0, 0, NULL); |
| 5010 | return 0; |
| 5011 | } |
| 5012 | |
| 5013 | |
| 5014 | /* |
| 5015 | * Returns true if the move is in a given list of moves. |
| 5016 | */ |
| 5017 | |
| 5018 | static int |
| 5019 | in_list(int move, int num_moves, int *moves) |
| 5020 | { |
| 5021 | int k; |
| 5022 | |
| 5023 | for (k = 0; k < num_moves; k++) |
| 5024 | if (moves[k] == move) |
| 5025 | return 1; |
| 5026 | return 0; |
| 5027 | } |
| 5028 | |
| 5029 | |
| 5030 | /* ================================================================ */ |
| 5031 | /* Move ordering */ |
| 5032 | /* ================================================================ */ |
| 5033 | |
| 5034 | /* Parameters used in the ordering of moves to try in the tactical |
| 5035 | * reading. |
| 5036 | */ |
| 5037 | |
| 5038 | /* 0 1 2 3 4 >4 */ |
| 5039 | static int defend_lib_score[6] = {-5, -4, 0, 3, 5, 50}; |
| 5040 | static int defend_not_adjacent_lib_score[5] = { 0, 0, 2, 3, 5}; |
| 5041 | static int defend_capture_score[6] = { 0, 6, 9, 13, 18, 24}; |
| 5042 | static int defend_atari_score[6] = { 0, 2, 4, 6, 7, 8}; |
| 5043 | static int defend_save_score[6] = { 0, 3, 6, 8, 10, 12}; |
| 5044 | static int defend_open_score[5] = { 0, 1, 2, 3, 4}; |
| 5045 | static int attack_own_lib_score[5] = {10, -4, 2, 3, 4}; |
| 5046 | static int attack_string_lib_score[6] = {-5, 2, 3, 7, 10, 19}; |
| 5047 | static int attack_capture_score[6] = {-4, 4, 10, 15, 20, 25}; |
| 5048 | static int attack_save_score[6] = { 0, 10, 13, 18, 21, 24}; |
| 5049 | static int attack_open_score[5] = { 0, 0, 2, 4, 4}; |
| 5050 | static int defend_not_edge_score = 5; |
| 5051 | static int attack_not_edge_score = 1; |
| 5052 | static int attack_ko_score = -15; |
| 5053 | static int cannot_defend_penalty = -20; |
| 5054 | static int safe_atari_score = 8; |
| 5055 | |
| 5056 | |
| 5057 | static void |
| 5058 | sgf_dumpmoves(struct reading_moves *moves, const char *funcname) |
| 5059 | { |
| 5060 | char buf[500]; |
| 5061 | char *pos; |
| 5062 | int i, chars; |
| 5063 | sprintf(buf, "Move order for %s: %n", funcname, &chars); |
| 5064 | pos = buf + chars; |
| 5065 | for (i = moves->num_tried; i < moves->num; i++) { |
| 5066 | sprintf(pos, "%c%d (%d) %n", |
| 5067 | J(moves->pos[i]) + 'A' + (J(moves->pos[i]) >= 8), |
| 5068 | board_size - I(moves->pos[i]), moves->score[i], &chars); |
| 5069 | pos += chars; |
| 5070 | } |
| 5071 | sgftreeAddComment(sgf_dumptree, buf); |
| 5072 | } |
| 5073 | |
| 5074 | |
| 5075 | /* The string at (str) is under attack. The moves.num moves in |
| 5076 | * (moves) for color have been deemed interesting in |
| 5077 | * the attack or defense of the group. Most of these moves will be |
| 5078 | * immediate liberties of the group. |
| 5079 | * |
| 5080 | * This function orders the moves in the order where the move most |
| 5081 | * likely to succeed to attack or defend the string will be first and |
| 5082 | * so on. |
| 5083 | * |
| 5084 | * Currently, this is defined as: |
| 5085 | * 1) Moves which let the defending string get more liberties are more |
| 5086 | * interesting. |
| 5087 | * 2) Moves adjacent to the most open liberties are more |
| 5088 | * interesting than those with fewer open liberties. |
| 5089 | * 3) Moves on the edge are less interesting. |
| 5090 | * |
| 5091 | * Moves below first_move are ignored and assumed to be sorted already. |
| 5092 | */ |
| 5093 | |
| 5094 | static void |
| 5095 | order_moves(int str, struct reading_moves *moves, int color, |
| 5096 | const char *funcname, int killer) |
| 5097 | { |
| 5098 | int string_color = board[str]; |
| 5099 | int string_libs = countlib(str); |
| 5100 | int r; |
| 5101 | int i, j; |
| 5102 | |
| 5103 | /* Don't bother sorting if only one move, or none at all. */ |
| 5104 | if (moves->num - moves->num_tried < 2) { |
| 5105 | /* But let's still have a single candidate in the sgf output */ |
| 5106 | if (sgf_dumptree && moves->num > moves->num_tried) |
| 5107 | sgf_dumpmoves(moves, funcname); |
| 5108 | return; |
| 5109 | } |
| 5110 | |
| 5111 | /* Assign a score to each move. */ |
| 5112 | for (r = moves->num_tried; r < moves->num; r++) { |
| 5113 | int move = moves->pos[r]; |
| 5114 | |
| 5115 | /* Look at the neighbors of this move and count the things we |
| 5116 | * find. Friendly and opponent stones are related to color, i.e. |
| 5117 | * the player to move, not to the color of the string. |
| 5118 | */ |
| 5119 | int number_edges = 0; /* outside board */ |
| 5120 | int number_same_string = 0; /* the string being attacked */ |
| 5121 | int number_own = 0; /* friendly stone */ |
| 5122 | int number_opponent = 0; /* opponent stone */ |
| 5123 | int captured_stones = 0; /* number of stones captured by this move */ |
| 5124 | int threatened_stones = 0; /* number of stones threatened by this move */ |
| 5125 | int saved_stones = 0; /* number of stones in atari saved */ |
| 5126 | int number_open = 0; /* empty intersection */ |
| 5127 | |
| 5128 | /* We let the incremental_board code do the heavy work. */ |
| 5129 | incremental_order_moves(move, color, str, &number_edges, |
| 5130 | &number_same_string, &number_own, |
| 5131 | &number_opponent, &captured_stones, |
| 5132 | &threatened_stones, &saved_stones, &number_open); |
| 5133 | |
| 5134 | if (0) |
| 5135 | gprintf("%o %1m values: %d %d %d %d %d %d %d %d\n", move, number_edges, |
| 5136 | number_same_string, number_own, number_opponent, captured_stones, |
| 5137 | threatened_stones, saved_stones, number_open); |
| 5138 | |
| 5139 | /* Different score strategies depending on whether the move is |
| 5140 | * attacking or defending the string. |
| 5141 | */ |
| 5142 | if (color == string_color) { |
| 5143 | /* Defense move. |
| 5144 | * |
| 5145 | * 1) Add twice the number of liberties the group receives by |
| 5146 | * extending to the intersection of the move, if more than one. |
| 5147 | * Only applicable if the move is adjacent to the group. |
| 5148 | */ |
| 5149 | |
| 5150 | int libs = approxlib(move, color, 10, NULL); |
| 5151 | if (number_same_string > 0) { |
| 5152 | if (libs > 5 || (libs == 4 && stackp > fourlib_depth)) |
| 5153 | moves->score[r] += defend_lib_score[5] + (libs - 4); |
| 5154 | else |
| 5155 | moves->score[r] += defend_lib_score[libs]; |
| 5156 | } |
| 5157 | else { |
| 5158 | /* Add points for the number of liberties the played stone |
| 5159 | * obtains when not adjacent to the attacked string. |
| 5160 | */ |
| 5161 | if (libs > 4) |
| 5162 | moves->score[r] += defend_not_adjacent_lib_score[4]; |
| 5163 | else |
| 5164 | moves->score[r] += defend_not_adjacent_lib_score[libs]; |
| 5165 | } |
| 5166 | |
| 5167 | /* 2) Add the number of open liberties near the move to its score. */ |
| 5168 | gg_assert(number_open <= 4); |
| 5169 | moves->score[r] += defend_open_score[number_open]; |
| 5170 | |
| 5171 | /* 3) Add a bonus if the move is not on the edge. |
| 5172 | */ |
| 5173 | if (number_edges == 0 || captured_stones > 0) |
| 5174 | moves->score[r] += defend_not_edge_score; |
| 5175 | |
| 5176 | /* 4) Add thrice the number of captured stones. */ |
| 5177 | if (captured_stones <= 5) |
| 5178 | moves->score[r] += defend_capture_score[captured_stones]; |
| 5179 | else |
| 5180 | moves->score[r] += defend_capture_score[5] + captured_stones; |
| 5181 | |
| 5182 | /* 5) Add points for stones put into atari, unless this is a |
| 5183 | * self atari. |
| 5184 | */ |
| 5185 | if (libs + captured_stones > 1) { |
| 5186 | if (threatened_stones <= 5) |
| 5187 | moves->score[r] += defend_atari_score[threatened_stones]; |
| 5188 | else |
| 5189 | moves->score[r] += defend_atari_score[5] + threatened_stones; |
| 5190 | } |
| 5191 | |
| 5192 | /* 6) Add a bonus for saved stones. */ |
| 5193 | if (saved_stones <= 5) |
| 5194 | moves->score[r] += defend_save_score[saved_stones]; |
| 5195 | else |
| 5196 | moves->score[r] += defend_save_score[5]; |
| 5197 | } |
| 5198 | else { |
| 5199 | /* Attack move. |
| 5200 | * |
| 5201 | * 1) Add the number of liberties the attacker gets when playing |
| 5202 | * there, but never more than four. |
| 5203 | */ |
| 5204 | int libs = approxlib(move, color, 4, NULL); |
| 5205 | if (libs > 4) |
| 5206 | libs = 4; |
| 5207 | moves->score[r] += attack_own_lib_score[libs]; |
| 5208 | |
| 5209 | if (libs == 0 && captured_stones == 1) |
| 5210 | moves->score[r] += attack_ko_score; |
| 5211 | |
| 5212 | /* 2) If the move is not a self atari and adjacent to the |
| 5213 | * string, add the number of liberties the opponent would |
| 5214 | * gain by playing there. If the string has two liberties, |
| 5215 | * self-ataris are also ok since they may be snapbacks, but |
| 5216 | * only if a single stone is sacrificed. |
| 5217 | */ |
| 5218 | if ((libs + captured_stones > 1 || (string_libs <= 2 && number_own == 0)) |
| 5219 | && number_same_string > 0) { |
| 5220 | int safe_atari; |
| 5221 | int liberties = approxlib(move, string_color, 5, NULL); |
| 5222 | if (liberties > 5 || (liberties == 4 && stackp > fourlib_depth)) |
| 5223 | liberties = 5; |
| 5224 | moves->score[r] += attack_string_lib_score[liberties]; |
| 5225 | |
| 5226 | safe_atari = (string_libs <= 2 && libs + captured_stones > 1); |
| 5227 | /* The defender can't play here without getting into atari, so |
| 5228 | * we probably souldn't either. |
| 5229 | */ |
| 5230 | if (liberties == 1 && saved_stones == 0 && !safe_atari) |
| 5231 | moves->score[r] += cannot_defend_penalty; |
| 5232 | |
| 5233 | /* Bonus if we put the attacked string into atari without |
| 5234 | * ourselves getting into atari. |
| 5235 | */ |
| 5236 | if (safe_atari) |
| 5237 | moves->score[r] += safe_atari_score; |
| 5238 | } |
| 5239 | |
| 5240 | /* 3) Add the number of open liberties near the move to its score. */ |
| 5241 | gg_assert(number_open <= 4); |
| 5242 | moves->score[r] += attack_open_score[number_open]; |
| 5243 | |
| 5244 | /* 4) Add a bonus if the move is not on the edge. */ |
| 5245 | if (number_edges == 0) |
| 5246 | moves->score[r] += attack_not_edge_score; |
| 5247 | |
| 5248 | /* 5) Add twice the number of captured stones. */ |
| 5249 | if (captured_stones <= 5) |
| 5250 | moves->score[r] += attack_capture_score[captured_stones]; |
| 5251 | else |
| 5252 | moves->score[r] += attack_capture_score[5]; |
| 5253 | |
| 5254 | /* 6) Add a bonus for saved stones. */ |
| 5255 | if (saved_stones <= 5) |
| 5256 | moves->score[r] += attack_save_score[saved_stones]; |
| 5257 | else |
| 5258 | moves->score[r] += attack_save_score[5]; |
| 5259 | } |
| 5260 | if (moves->pos[r] == killer) |
| 5261 | moves->score[r] += 50; |
| 5262 | } |
| 5263 | |
| 5264 | /* Now sort the moves. We use selection sort since this array will |
| 5265 | * probably never be more than 10 moves long. In this case, the |
| 5266 | * overhead imposed by quicksort will probably overshadow the gains |
| 5267 | * given by the O(n*log(n)) behaviour over the O(n^2) behaviour of |
| 5268 | * selection sort. |
| 5269 | */ |
| 5270 | for (i = moves->num_tried; i < moves->num-1; i++) { |
| 5271 | int maxscore = moves->score[i]; |
| 5272 | int max_at = 0; /* This is slightly faster than max_at = i. */ |
| 5273 | |
| 5274 | /* Find the move with the biggest score. */ |
| 5275 | for (j = i + 1; j < moves->num; j++) { |
| 5276 | if (moves->score[j] > maxscore) { |
| 5277 | maxscore = moves->score[j]; |
| 5278 | max_at = j; |
| 5279 | } |
| 5280 | } |
| 5281 | |
| 5282 | /* Now exchange the move at i with the move at max_at. |
| 5283 | * Don't forget to exchange the scores as well. |
| 5284 | */ |
| 5285 | if (max_at != 0) { |
| 5286 | int temp = moves->pos[max_at]; |
| 5287 | const char *temp_message = moves->message[max_at]; |
| 5288 | |
| 5289 | moves->pos[max_at] = moves->pos[i]; |
| 5290 | moves->score[max_at] = moves->score[i]; |
| 5291 | moves->message[max_at] = moves->message[i]; |
| 5292 | |
| 5293 | moves->pos[i] = temp; |
| 5294 | moves->score[i] = maxscore; |
| 5295 | moves->message[i] = temp_message; |
| 5296 | } |
| 5297 | } |
| 5298 | |
| 5299 | |
| 5300 | if (0) { |
| 5301 | gprintf("%oVariation %d:\n", count_variations); |
| 5302 | for (i = moves->num_tried; i < moves->num; i++) |
| 5303 | gprintf("%o %1M %d\n", moves->pos[i], moves->score[i]); |
| 5304 | } |
| 5305 | |
| 5306 | if (sgf_dumptree) |
| 5307 | sgf_dumpmoves(moves, funcname); |
| 5308 | } |
| 5309 | |
| 5310 | |
| 5311 | /* Set new values for the move ordering parameters. */ |
| 5312 | void |
| 5313 | tune_move_ordering(int params[MOVE_ORDERING_PARAMETERS]) |
| 5314 | { |
| 5315 | int k; |
| 5316 | for (k = 0; k < 6; k++) { |
| 5317 | defend_lib_score[k] = params[k]; |
| 5318 | if (k < 5) |
| 5319 | defend_not_adjacent_lib_score[k] = params[k + 6]; |
| 5320 | defend_capture_score[k] = params[k + 11]; |
| 5321 | defend_atari_score[k] = params[k + 17]; |
| 5322 | defend_save_score[k] = params[k + 23]; |
| 5323 | if (k < 5) { |
| 5324 | defend_open_score[k] = params[k + 29]; |
| 5325 | attack_own_lib_score[k] = params[k + 34]; |
| 5326 | } |
| 5327 | attack_string_lib_score[k] = params[k + 39]; |
| 5328 | attack_capture_score[k] = params[k + 45]; |
| 5329 | attack_save_score[k] = params[k + 51]; |
| 5330 | if (k < 5) |
| 5331 | attack_open_score[k] = params[k + 57]; |
| 5332 | } |
| 5333 | defend_not_edge_score = params[62]; |
| 5334 | attack_not_edge_score = params[63]; |
| 5335 | attack_ko_score = params[64]; |
| 5336 | cannot_defend_penalty = params[65]; |
| 5337 | safe_atari_score = params[66]; |
| 5338 | |
| 5339 | if (verbose) { |
| 5340 | gprintf("static int defend_lib_score[6] = {%d, %d, %d, %d, %d, %d};\n", |
| 5341 | defend_lib_score[0], defend_lib_score[1], |
| 5342 | defend_lib_score[2], defend_lib_score[3], |
| 5343 | defend_lib_score[4], defend_lib_score[5]); |
| 5344 | gprintf("static int defend_not_adjacent_lib_score[5] = {%d, %d, %d, %d, %d};\n", |
| 5345 | defend_not_adjacent_lib_score[0], defend_not_adjacent_lib_score[1], |
| 5346 | defend_not_adjacent_lib_score[2], defend_not_adjacent_lib_score[3], |
| 5347 | defend_not_adjacent_lib_score[4]); |
| 5348 | gprintf("static int defend_capture_score[6] = {%d, %d, %d, %d, %d, %d};\n", |
| 5349 | defend_capture_score[0], defend_capture_score[1], |
| 5350 | defend_capture_score[2], defend_capture_score[3], |
| 5351 | defend_capture_score[4], defend_capture_score[5]); |
| 5352 | gprintf("static int defend_atari_score[6] = {%d, %d, %d, %d, %d, %d};\n", |
| 5353 | defend_atari_score[0], defend_atari_score[1], |
| 5354 | defend_atari_score[2], defend_atari_score[3], |
| 5355 | defend_atari_score[4], defend_atari_score[5]); |
| 5356 | gprintf("static int defend_save_score[6] = {%d, %d, %d, %d, %d, %d};\n", |
| 5357 | defend_save_score[0], defend_save_score[1], |
| 5358 | defend_save_score[2], defend_save_score[3], |
| 5359 | defend_save_score[4], defend_save_score[5]); |
| 5360 | gprintf("static int defend_open_score[5] = {%d, %d, %d, %d, %d};\n", |
| 5361 | defend_open_score[0], defend_open_score[1], |
| 5362 | defend_open_score[2], defend_open_score[3], |
| 5363 | defend_open_score[4]); |
| 5364 | gprintf("static int attack_own_lib_score[5] = {%d, %d, %d, %d, %d};\n", |
| 5365 | attack_own_lib_score[0], attack_own_lib_score[1], |
| 5366 | attack_own_lib_score[2], attack_own_lib_score[3], |
| 5367 | attack_own_lib_score[4]); |
| 5368 | gprintf("static int attack_string_lib_score[6] = {%d, %d, %d, %d, %d, %d};\n", |
| 5369 | attack_string_lib_score[0], attack_string_lib_score[1], |
| 5370 | attack_string_lib_score[2], attack_string_lib_score[3], |
| 5371 | attack_string_lib_score[4], attack_string_lib_score[5]); |
| 5372 | gprintf("static int attack_capture_score[6] = {%d, %d, %d, %d, %d, %d};\n", |
| 5373 | attack_capture_score[0], attack_capture_score[1], |
| 5374 | attack_capture_score[2], attack_capture_score[3], |
| 5375 | attack_capture_score[4], attack_capture_score[5]); |
| 5376 | gprintf("static int attack_save_score[6] = {%d, %d, %d, %d, %d, %d};\n", |
| 5377 | attack_save_score[0], attack_save_score[1], |
| 5378 | attack_save_score[2], attack_save_score[3], |
| 5379 | attack_save_score[4], attack_save_score[5]); |
| 5380 | gprintf("static int attack_open_score[5] = {%d, %d, %d, %d, %d};\n", |
| 5381 | attack_open_score[0], attack_open_score[1], |
| 5382 | attack_open_score[2], attack_open_score[3], |
| 5383 | attack_open_score[4]); |
| 5384 | gprintf("static int defend_not_edge_score = %d;\n", defend_not_edge_score); |
| 5385 | gprintf("static int attack_not_edge_score = %d;\n", attack_not_edge_score); |
| 5386 | gprintf("static int attack_ko_score = %d;\n", attack_ko_score); |
| 5387 | gprintf("static int cannot_defend_penalty = %d;\n", cannot_defend_penalty); |
| 5388 | gprintf("static int safe_atari_score = %d;\n", safe_atari_score); |
| 5389 | } |
| 5390 | } |
| 5391 | |
| 5392 | |
| 5393 | |
| 5394 | /* ================================================================ */ |
| 5395 | /* Reading utilities */ |
| 5396 | /* ================================================================ */ |
| 5397 | |
| 5398 | |
| 5399 | static int safe_move_cache[BOARDMAX][2]; |
| 5400 | static int safe_move_cache_when[BOARDMAX][2]; |
| 5401 | static void clear_safe_move_cache(void); |
| 5402 | |
| 5403 | static void |
| 5404 | clear_safe_move_cache(void) |
| 5405 | { |
| 5406 | int k; |
| 5407 | |
| 5408 | for (k = BOARDMIN; k < BOARDMAX; k++) { |
| 5409 | safe_move_cache_when[k][0] = -1; |
| 5410 | safe_move_cache_when[k][1] = -1; |
| 5411 | } |
| 5412 | } |
| 5413 | |
| 5414 | /* safe_move(move, color) checks whether a move at (move) is illegal |
| 5415 | * or can immediately be captured. If stackp==0 the result is cached. |
| 5416 | * If the move only can be captured by a ko, it's considered safe. |
| 5417 | * This may or may not be a good convention. |
| 5418 | * |
| 5419 | * For performance reasons, the result of this function is cached. |
| 5420 | */ |
| 5421 | |
| 5422 | int |
| 5423 | safe_move(int move, int color) |
| 5424 | { |
| 5425 | int safe = 0; |
| 5426 | static int initialized = 0; |
| 5427 | int ko_move; |
| 5428 | |
| 5429 | if (!initialized) { |
| 5430 | clear_safe_move_cache(); |
| 5431 | initialized = 1; |
| 5432 | } |
| 5433 | |
| 5434 | /* If we have this position cached, use the previous value. |
| 5435 | * Only use cached values when stackp is 0 and reading is not being done |
| 5436 | * at a modified depth. |
| 5437 | */ |
| 5438 | if (stackp == 0 |
| 5439 | && depth_offset == 0 |
| 5440 | && safe_move_cache_when[move][color == BLACK] == position_number) |
| 5441 | return safe_move_cache[move][color == BLACK]; |
| 5442 | |
| 5443 | /* Otherwise calculate the value... */ |
| 5444 | if (komaster_trymove(move, color, "safe_move", 0, &ko_move, 1)) { |
| 5445 | safe = REVERSE_RESULT(attack(move, NULL)); |
| 5446 | if (ko_move && safe != 0) |
| 5447 | safe = KO_B; |
| 5448 | popgo(); |
| 5449 | } |
| 5450 | |
| 5451 | /* ...and store it in the cache. |
| 5452 | * FIXME: Only store result in cache when we're working at |
| 5453 | * full depth. |
| 5454 | * |
| 5455 | * Comment: This is currently not a problem since no reduced depth |
| 5456 | * reading is performed. |
| 5457 | */ |
| 5458 | if (stackp == 0 && depth_offset == 0) { |
| 5459 | if (0) |
| 5460 | gprintf("Safe move at %1m for %s cached when depth=%d, position number=%d\n", |
| 5461 | move, color_to_string(color), depth, position_number); |
| 5462 | safe_move_cache_when[move][color == BLACK] = position_number; |
| 5463 | safe_move_cache[move][color == BLACK] = safe; |
| 5464 | } |
| 5465 | |
| 5466 | return safe; |
| 5467 | } |
| 5468 | |
| 5469 | |
| 5470 | /* Checks if a move by color makes an opponent move at pos a self atari. |
| 5471 | */ |
| 5472 | int |
| 5473 | does_secure(int color, int move, int pos) |
| 5474 | { |
| 5475 | int result = 0; |
| 5476 | if (trymove(move, color, NULL, NO_MOVE)) { |
| 5477 | if (is_self_atari(pos, OTHER_COLOR(color))) |
| 5478 | result = 1; |
| 5479 | popgo(); |
| 5480 | } |
| 5481 | |
| 5482 | return result; |
| 5483 | } |
| 5484 | |
| 5485 | |
| 5486 | /* ===================== Statistics ============================= */ |
| 5487 | |
| 5488 | |
| 5489 | /* Clear statistics. */ |
| 5490 | void |
| 5491 | reset_reading_node_counter() |
| 5492 | { |
| 5493 | reading_node_counter = 0; |
| 5494 | } |
| 5495 | |
| 5496 | |
| 5497 | /* Retrieve statistics. */ |
| 5498 | int |
| 5499 | get_reading_node_counter() |
| 5500 | { |
| 5501 | return reading_node_counter; |
| 5502 | } |
| 5503 | |
| 5504 | /* ============ Reading shadow =============== */ |
| 5505 | |
| 5506 | /* Draw the reading shadow, for debugging purposes */ |
| 5507 | |
| 5508 | void |
| 5509 | draw_reading_shadow() |
| 5510 | { |
| 5511 | int i, j; |
| 5512 | int c = ' '; |
| 5513 | int pos; |
| 5514 | |
| 5515 | start_draw_board(); |
| 5516 | |
| 5517 | for (i = 0; i < board_size; i++) { |
| 5518 | fprintf(stderr, "\n%2d", board_size - i); |
| 5519 | |
| 5520 | for (j = 0; j < board_size; j++) { |
| 5521 | pos = POS(i, j); |
| 5522 | if (!shadow[pos] && board[pos] == EMPTY) |
| 5523 | c = '.'; |
| 5524 | else if (!shadow[pos] && board[pos] == WHITE) |
| 5525 | c = 'O'; |
| 5526 | else if (!shadow[pos] && board[pos] == BLACK) |
| 5527 | c = 'X'; |
| 5528 | if (shadow[pos] && board[pos] == EMPTY) |
| 5529 | c = ','; |
| 5530 | else if (shadow[pos] && board[pos] == WHITE) |
| 5531 | c = 'o'; |
| 5532 | else if (shadow[pos] && board[pos] == BLACK) |
| 5533 | c = 'x'; |
| 5534 | |
| 5535 | fprintf(stderr, " %c", c); |
| 5536 | } |
| 5537 | |
| 5538 | fprintf(stderr, " %d", board_size - i); |
| 5539 | } |
| 5540 | |
| 5541 | end_draw_board(); |
| 5542 | } |
| 5543 | |
| 5544 | |
| 5545 | /* ================================================================ */ |
| 5546 | /* Code for special purposes. */ |
| 5547 | /* ================================================================ */ |
| 5548 | |
| 5549 | /* simple_ladder(str, &move) tries to capture a string (str) |
| 5550 | * with exactly two liberties under simplified assumptions, which are |
| 5551 | * adequate in a ladder. The rules are as follows: |
| 5552 | * |
| 5553 | * 1. The attacker is allowed to play at each of the two liberties, |
| 5554 | * but no other move. If the move was legal, the string now has |
| 5555 | * exactly one liberty. |
| 5556 | * 2. The defender must move out of atari. This can only be done by |
| 5557 | * either extending at the liberty or capturing a neighboring |
| 5558 | * string which was in atari. All such moves may be tested. |
| 5559 | * 3. Depending on the resulting number of liberties of the string |
| 5560 | * after the defender's move, we value each node as follows: |
| 5561 | * |
| 5562 | * 3 or more liberties: the attack has failed |
| 5563 | * 2 liberties: recurse |
| 5564 | * 1 liberty: the attack has succeeded |
| 5565 | * |
| 5566 | * illegal move for the defender: successful attack |
| 5567 | * illegal move for the attacker: failed attack |
| 5568 | * |
| 5569 | * Return codes are as usual 0 for failure, WIN for success, KO_A for |
| 5570 | * a ko where the defender must make the first ko threat and KO_B for |
| 5571 | * a ko where the attacked has to make the first threat. If the attack |
| 5572 | * was successful, (*move) contains the attacking move, unless it is a |
| 5573 | * null pointer. |
| 5574 | * |
| 5575 | * The differences compared to the attack2()/defend1() combination for |
| 5576 | * reading ladders is that this one is a strict ladder reader which |
| 5577 | * never allows the defender to have more than one liberty when it's |
| 5578 | * in turn to move. This has a number of consequences. |
| 5579 | * |
| 5580 | * 1. This function will miss tactical captures involving other |
| 5581 | * techniques than the ladder. |
| 5582 | * |
| 5583 | * 2. This function is faster because it gives up faster when the |
| 5584 | * ladder doesn't work. In particular it can't branch out in a huge |
| 5585 | * tree of exotic variations. |
| 5586 | * |
| 5587 | * 3. This function always reads ladders to the very end. There are no |
| 5588 | * depth limits or other assumptions to stop reading prematurely. |
| 5589 | * |
| 5590 | * 4. If this function returns WIN, it is guaranteed that the defender |
| 5591 | * has no way whatsoever to escape, all possibilities are tried. |
| 5592 | * The converse is definitely not true. |
| 5593 | */ |
| 5594 | |
| 5595 | int |
| 5596 | simple_ladder(int str, int *move) |
| 5597 | { |
| 5598 | int color = board[str]; |
| 5599 | int other = OTHER_COLOR(color); |
| 5600 | int apos; |
| 5601 | int libs[2]; |
| 5602 | int savemove = 0; |
| 5603 | int savecode = 0; |
| 5604 | int dcode; |
| 5605 | int k; |
| 5606 | struct reading_moves moves; |
| 5607 | |
| 5608 | SETUP_TRACE_INFO("simple_ladder", str); |
| 5609 | reading_node_counter++; |
| 5610 | moves.num = 0; |
| 5611 | moves.num_tried = 0; |
| 5612 | |
| 5613 | str = find_origin(str); |
| 5614 | ASSERT1(IS_STONE(board[str]), str); |
| 5615 | ASSERT1(countlib(str) == 2, str); |
| 5616 | |
| 5617 | /* Give up if we attacked depending on ko for too long. */ |
| 5618 | if (stackp > depth + 20 && get_komaster() == OTHER_COLOR(board[str])) { |
| 5619 | SGFTRACE(0, 0, NULL); |
| 5620 | if (move) |
| 5621 | *move = PASS_MOVE; |
| 5622 | return 0; |
| 5623 | } |
| 5624 | |
| 5625 | /* Get the two liberties of (str). */ |
| 5626 | findlib(str, 2, libs); |
| 5627 | |
| 5628 | /* If the defender can get enough liberties by playing one of these |
| 5629 | * two, then we have no choice but to block there and consequently, |
| 5630 | * it is unnecesary to try the other liberty. |
| 5631 | */ |
| 5632 | |
| 5633 | if (approxlib(libs[0], color, 4, NULL) <= 3) |
| 5634 | ADD_CANDIDATE_MOVE(libs[1], 0, moves, "simple_ladder"); |
| 5635 | if (approxlib(libs[1], color, 4, NULL) <= 3) |
| 5636 | ADD_CANDIDATE_MOVE(libs[0], 0, moves, "simple_ladder"); |
| 5637 | |
| 5638 | order_moves(str, &moves, other, read_function_name, NO_MOVE); |
| 5639 | |
| 5640 | for (k = 0; k < moves.num; k++) { |
| 5641 | int ko_move; |
| 5642 | |
| 5643 | apos = moves.pos[k]; |
| 5644 | if (komaster_trymove(apos, other, moves.message[k], str, |
| 5645 | &ko_move, savecode == 0)) { |
| 5646 | if (!ko_move) { |
| 5647 | dcode = simple_ladder_defend(str, NULL); |
| 5648 | if (dcode != WIN) { |
| 5649 | if (dcode == 0) { |
| 5650 | popgo(); |
| 5651 | SGFTRACE(apos, WIN, "attack effective"); |
| 5652 | if (move) |
| 5653 | *move = apos; |
| 5654 | return WIN; |
| 5655 | } |
| 5656 | UPDATE_SAVED_KO_RESULT(savecode, savemove, dcode, apos); |
| 5657 | } |
| 5658 | } |
| 5659 | else { |
| 5660 | if (simple_ladder_defend(str, NULL) != WIN) { |
| 5661 | savemove = apos; |
| 5662 | savecode = KO_B; |
| 5663 | } |
| 5664 | } |
| 5665 | popgo(); |
| 5666 | } |
| 5667 | } |
| 5668 | |
| 5669 | RETURN_RESULT(savecode, savemove, move, "saved move"); |
| 5670 | } |
| 5671 | |
| 5672 | |
| 5673 | static int |
| 5674 | simple_ladder_defend(int str, int *move) |
| 5675 | { |
| 5676 | int color = board[str]; |
| 5677 | int xpos; |
| 5678 | int lib; |
| 5679 | struct reading_moves moves; |
| 5680 | int savemove = 0; |
| 5681 | int savecode = 0; |
| 5682 | int k; |
| 5683 | |
| 5684 | SETUP_TRACE_INFO("simple_ladder_defend", str); |
| 5685 | reading_node_counter++; |
| 5686 | |
| 5687 | ASSERT1(IS_STONE(board[str]), str); |
| 5688 | ASSERT1(countlib(str) == 1, str); |
| 5689 | |
| 5690 | /* lib will be the liberty of the string. */ |
| 5691 | findlib(str, 1, &lib); |
| 5692 | |
| 5693 | moves.pos[0] = lib; |
| 5694 | moves.score[0] = 0; |
| 5695 | moves.message[0] = "liberty"; |
| 5696 | moves.num = 1; |
| 5697 | moves.num_tried = 0; |
| 5698 | |
| 5699 | break_chain_moves(str, &moves); |
| 5700 | order_moves(str, &moves, color, read_function_name, NO_MOVE); |
| 5701 | |
| 5702 | for (k = 0; k < moves.num; k++) { |
| 5703 | int ko_move; |
| 5704 | |
| 5705 | xpos = moves.pos[k]; |
| 5706 | if (komaster_trymove(xpos, color, moves.message[k], str, |
| 5707 | &ko_move, savecode == 0)) { |
| 5708 | int acode; |
| 5709 | int new_libs = countlib(str); |
| 5710 | if (new_libs > 2) |
| 5711 | acode = 0; |
| 5712 | else if (new_libs < 2) |
| 5713 | acode = WIN; |
| 5714 | else |
| 5715 | acode = simple_ladder(str, NULL); |
| 5716 | popgo(); |
| 5717 | |
| 5718 | if (!ko_move) |
| 5719 | CHECK_RESULT(savecode, savemove, acode, xpos, move, |
| 5720 | "defense effective"); |
| 5721 | else { |
| 5722 | if (acode != WIN) { |
| 5723 | savemove = xpos; |
| 5724 | savecode = KO_B; |
| 5725 | } |
| 5726 | } |
| 5727 | } |
| 5728 | } |
| 5729 | |
| 5730 | RETURN_RESULT(savecode, savemove, move, "saved move"); |
| 5731 | } |
| 5732 | |
| 5733 | |
| 5734 | /* |
| 5735 | * Local Variables: |
| 5736 | * tab-width: 8 |
| 5737 | * c-basic-offset: 2 |
| 5738 | * End: |
| 5739 | */ |