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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 | */ |