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/* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * *\
* This is GNU Go, a Go program. Contact gnugo@gnu.org, or see *
* http://www.gnu.org/software/gnugo/ for more information. *
* *
* Copyright 1999, 2000, 2001, 2002, 2003, 2004, 2005, 2006, 2007, *
* 2008 and 2009 by the Free Software Foundation. *
* *
* This program is free software; you can redistribute it and/or *
* modify it under the terms of the GNU General Public License as *
* published by the Free Software Foundation - version 3 or *
* (at your option) any later version. *
* *
* This program is distributed in the hope that it will be useful, *
* but WITHOUT ANY WARRANTY; without even the implied warranty of *
* MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the *
* GNU General Public License in file COPYING for more details. *
* *
* You should have received a copy of the GNU General Public *
* License along with this program; if not, write to the Free *
* Software Foundation, Inc., 51 Franklin Street, Fifth Floor, *
* Boston, MA 02111, USA. *
\* * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * */
#ifndef _RANDOM_H_
#define _RANDOM_H_
/* This random number generator produces 32 bit unsigned integers, no
* more, no less. Internally in the algorithm and for storing the
* state we need a type that is at least 32 bits wide. A longer type
* doesn't hurt but means a waste of bits.
*
* ISO C guarantees that an unsigned long always is at least 32 bits.
* It is not uncommon, however, that it is longer. An unsigned int is
* not guaranteed to be more than 16 bits wide, but on modern
* platforms we can be certain that this type too is 32 bits (or
* more). Also the GNU Coding Standards explicitly state that the
* possibility of ints shorter than 32 bits should be ignored.
*
* We could make a typedef here to choose exactly which type to use.
* In order to avoid various complications in the interface to the
* random number generator, however, we prefer to consistently use
* unsigned int internally and we assume this type to be at least 32
* bits wide.
*/
/* Internal state of the random number generator. */
struct gg_rand_state {
unsigned int x[25]; /* Internal state. */
int k; /* Word counter. */
};
/* Seed the random number generator. If an unsigned int is larger than
* 32 bits, only the 32 least significant bits are used for seeding.
*/
void gg_srand(unsigned int seed);
/* Obtain one random integer value in the interval [0, 2^31-1]. */
int gg_rand(void);
/* Obtain one random integer value in the interval [0, 2^32-1]. */
unsigned int gg_urand(void);
/* Obtain one random floating point value in the half open interval
* [0.0, 1.0).
*
* If the value is converted to a floating point type with less than
* 32 bits mantissa (or if the double type should happen to be
* unusually short), the value 1.0 may be attained.
*/
double gg_drand(void);
/* Retrieve the internal state of the random generator. */
void gg_get_rand_state(struct gg_rand_state *state);
/* Set the internal state of the random number generator. */
void gg_set_rand_state(struct gg_rand_state *state);
#endif /* _RANDOM_H_ */
/*
* Local Variables:
* tab-width: 8
* c-basic-offset: 2
* End:
*/
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