| 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 | #ifndef _RANDOM_H_ |
| 25 | #define _RANDOM_H_ |
| 26 | |
| 27 | /* This random number generator produces 32 bit unsigned integers, no |
| 28 | * more, no less. Internally in the algorithm and for storing the |
| 29 | * state we need a type that is at least 32 bits wide. A longer type |
| 30 | * doesn't hurt but means a waste of bits. |
| 31 | * |
| 32 | * ISO C guarantees that an unsigned long always is at least 32 bits. |
| 33 | * It is not uncommon, however, that it is longer. An unsigned int is |
| 34 | * not guaranteed to be more than 16 bits wide, but on modern |
| 35 | * platforms we can be certain that this type too is 32 bits (or |
| 36 | * more). Also the GNU Coding Standards explicitly state that the |
| 37 | * possibility of ints shorter than 32 bits should be ignored. |
| 38 | * |
| 39 | * We could make a typedef here to choose exactly which type to use. |
| 40 | * In order to avoid various complications in the interface to the |
| 41 | * random number generator, however, we prefer to consistently use |
| 42 | * unsigned int internally and we assume this type to be at least 32 |
| 43 | * bits wide. |
| 44 | */ |
| 45 | |
| 46 | /* Internal state of the random number generator. */ |
| 47 | struct gg_rand_state { |
| 48 | unsigned int x[25]; /* Internal state. */ |
| 49 | int k; /* Word counter. */ |
| 50 | }; |
| 51 | |
| 52 | /* Seed the random number generator. If an unsigned int is larger than |
| 53 | * 32 bits, only the 32 least significant bits are used for seeding. |
| 54 | */ |
| 55 | void gg_srand(unsigned int seed); |
| 56 | |
| 57 | /* Obtain one random integer value in the interval [0, 2^31-1]. */ |
| 58 | int gg_rand(void); |
| 59 | |
| 60 | /* Obtain one random integer value in the interval [0, 2^32-1]. */ |
| 61 | unsigned int gg_urand(void); |
| 62 | |
| 63 | /* Obtain one random floating point value in the half open interval |
| 64 | * [0.0, 1.0). |
| 65 | * |
| 66 | * If the value is converted to a floating point type with less than |
| 67 | * 32 bits mantissa (or if the double type should happen to be |
| 68 | * unusually short), the value 1.0 may be attained. |
| 69 | */ |
| 70 | double gg_drand(void); |
| 71 | |
| 72 | /* Retrieve the internal state of the random generator. */ |
| 73 | void gg_get_rand_state(struct gg_rand_state *state); |
| 74 | |
| 75 | /* Set the internal state of the random number generator. */ |
| 76 | void gg_set_rand_state(struct gg_rand_state *state); |
| 77 | |
| 78 | |
| 79 | #endif /* _RANDOM_H_ */ |
| 80 | |
| 81 | |
| 82 | /* |
| 83 | * Local Variables: |
| 84 | * tab-width: 8 |
| 85 | * c-basic-offset: 2 |
| 86 | * End: |
| 87 | */ |