1 /* GLIB - Library of useful routines for C programming
2 * Copyright (C) 1995-1997 Peter Mattis, Spencer Kimball and Josh MacDonald
4 * This library is free software; you can redistribute it and/or
5 * modify it under the terms of the GNU Lesser General Public
6 * License as published by the Free Software Foundation; either
7 * version 2 of the License, or (at your option) any later version.
9 * This library is distributed in the hope that it will be useful,
10 * but WITHOUT ANY WARRANTY; without even the implied warranty of
11 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE. See the GNU
12 * Lesser General Public License for more details.
14 * You should have received a copy of the GNU Lesser General Public
15 * License along with this library; if not, see <http://www.gnu.org/licenses/>.
18 /* Originally developed and coded by Makoto Matsumoto and Takuji
19 * Nishimura. Please mail <matumoto@math.keio.ac.jp>, if you're using
20 * code from this file in your own programs or libraries.
21 * Further information on the Mersenne Twister can be found at
22 * http://www.math.sci.hiroshima-u.ac.jp/~m-mat/MT/emt.html
23 * This code was adapted to glib by Sebastian Wilhelmi.
27 * Modified by the GLib Team and others 1997-2000. See the AUTHORS
28 * file for a list of people on the GLib Team. See the ChangeLog
29 * files for a list of changes. These files are distributed with
30 * GLib at ftp://ftp.gtk.org/pub/gtk/.
44 #include <sys/types.h>
50 #include "gtestutils.h"
62 * SECTION:random_numbers
63 * @title: Random Numbers
64 * @short_description: pseudo-random number generator
66 * The following functions allow you to use a portable, fast and good
67 * pseudo-random number generator (PRNG).
69 * Do not use this API for cryptographic purposes such as key
70 * generation, nonces, salts or one-time pads.
72 * This PRNG is suitable for non-cryptographic use such as in games
73 * (shuffling a card deck, generating levels), generating data for a
74 * test suite, etc. If you need random data for cryptographic
75 * purposes, it is recommended to use platform-specific APIs such as
76 * <literal>/dev/random</literal> on Unix, or CryptGenRandom() on
79 * GRand uses the Mersenne Twister PRNG, which was originally
80 * developed by Makoto Matsumoto and Takuji Nishimura. Further
81 * information can be found at
82 * [this page](http://www.math.sci.hiroshima-u.ac.jp/~m-mat/MT/emt.html).
84 * If you just need a random number, you simply call the g_random_*
85 * functions, which will create a globally used #GRand and use the
86 * according g_rand_* functions internally. Whenever you need a
87 * stream of reproducible random numbers, you better create a
88 * #GRand yourself and use the g_rand_* functions directly, which
89 * will also be slightly faster. Initializing a #GRand with a
90 * certain seed will produce exactly the same series of random
91 * numbers on all platforms. This can thus be used as a seed for
94 * The g_rand*_range functions will return high quality equally
95 * distributed random numbers, whereas for example the
96 * <literal>(g_random_int()%max)</literal> approach often
97 * doesn't yield equally distributed numbers.
99 * GLib changed the seeding algorithm for the pseudo-random number
100 * generator Mersenne Twister, as used by #GRand. This was necessary,
101 * because some seeds would yield very bad pseudo-random streams.
102 * Also the pseudo-random integers generated by g_rand*_int_range()
103 * will have a slightly better equal distribution with the new
106 * The original seeding and generation algorithms, as found in
107 * GLib 2.0.x, can be used instead of the new ones by setting the
108 * environment variable `G_RANDOM_VERSION` to the value of '2.0'.
109 * Use the GLib-2.0 algorithms only if you have sequences of numbers
110 * generated with Glib-2.0 that you need to reproduce exactly.
116 * The GRand struct is an opaque data structure. It should only be
117 * accessed through the g_rand_* functions.
120 G_LOCK_DEFINE_STATIC (global_random);
122 /* Period parameters */
125 #define MATRIX_A 0x9908b0df /* constant vector a */
126 #define UPPER_MASK 0x80000000 /* most significant w-r bits */
127 #define LOWER_MASK 0x7fffffff /* least significant r bits */
129 /* Tempering parameters */
130 #define TEMPERING_MASK_B 0x9d2c5680
131 #define TEMPERING_MASK_C 0xefc60000
132 #define TEMPERING_SHIFT_U(y) (y >> 11)
133 #define TEMPERING_SHIFT_S(y) (y << 7)
134 #define TEMPERING_SHIFT_T(y) (y << 15)
135 #define TEMPERING_SHIFT_L(y) (y >> 18)
138 get_random_version (void)
140 static gsize initialized = FALSE;
141 static guint random_version;
143 if (g_once_init_enter (&initialized))
145 const gchar *version_string = g_getenv ("G_RANDOM_VERSION");
146 if (!version_string || version_string[0] == '\000' ||
147 strcmp (version_string, "2.2") == 0)
149 else if (strcmp (version_string, "2.0") == 0)
153 g_warning ("Unknown G_RANDOM_VERSION \"%s\". Using version 2.2.",
157 g_once_init_leave (&initialized, TRUE);
160 return random_version;
165 guint32 mt[N]; /* the array for the state vector */
170 * g_rand_new_with_seed:
171 * @seed: a value to initialize the random number generator
173 * Creates a new random number generator initialized with @seed.
175 * Return value: the new #GRand
178 g_rand_new_with_seed (guint32 seed)
180 GRand *rand = g_new0 (GRand, 1);
181 g_rand_set_seed (rand, seed);
186 * g_rand_new_with_seed_array:
187 * @seed: an array of seeds to initialize the random number generator
188 * @seed_length: an array of seeds to initialize the random number
191 * Creates a new random number generator initialized with @seed.
193 * Return value: the new #GRand
198 g_rand_new_with_seed_array (const guint32 *seed,
201 GRand *rand = g_new0 (GRand, 1);
202 g_rand_set_seed_array (rand, seed, seed_length);
209 * Creates a new random number generator initialized with a seed taken
210 * either from `/dev/urandom` (if existing) or from the current time
213 * On Windows, the seed is taken from rand_s().
215 * Return value: the new #GRand
222 static gboolean dev_urandom_exists = TRUE;
225 if (dev_urandom_exists)
231 dev_urandom = fopen("/dev/urandom", "rb");
233 while G_UNLIKELY (dev_urandom == NULL && errno == EINTR);
239 setvbuf (dev_urandom, NULL, _IONBF, 0);
243 r = fread (seed, sizeof (seed), 1, dev_urandom);
245 while G_UNLIKELY (errno == EINTR);
248 dev_urandom_exists = FALSE;
250 fclose (dev_urandom);
253 dev_urandom_exists = FALSE;
256 if (!dev_urandom_exists)
258 g_get_current_time (&now);
259 seed[0] = now.tv_sec;
260 seed[1] = now.tv_usec;
262 seed[3] = getppid ();
264 #else /* G_OS_WIN32 */
267 for (i = 0; i < G_N_ELEMENTS (seed); i++)
271 return g_rand_new_with_seed_array (seed, 4);
278 * Frees the memory allocated for the #GRand.
281 g_rand_free (GRand *rand)
283 g_return_if_fail (rand != NULL);
292 * Copies a #GRand into a new one with the same exact state as before.
293 * This way you can take a snapshot of the random number generator for
296 * Return value: the new #GRand
301 g_rand_copy (GRand *rand)
305 g_return_val_if_fail (rand != NULL, NULL);
307 new_rand = g_new0 (GRand, 1);
308 memcpy (new_rand, rand, sizeof (GRand));
316 * @seed: a value to reinitialize the random number generator
318 * Sets the seed for the random number generator #GRand to @seed.
321 g_rand_set_seed (GRand *rand,
324 g_return_if_fail (rand != NULL);
326 switch (get_random_version ())
329 /* setting initial seeds to mt[N] using */
330 /* the generator Line 25 of Table 1 in */
331 /* [KNUTH 1981, The Art of Computer Programming */
332 /* Vol. 2 (2nd Ed.), pp102] */
334 if (seed == 0) /* This would make the PRNG produce only zeros */
335 seed = 0x6b842128; /* Just set it to another number */
338 for (rand->mti=1; rand->mti<N; rand->mti++)
339 rand->mt[rand->mti] = (69069 * rand->mt[rand->mti-1]);
343 /* See Knuth TAOCP Vol2. 3rd Ed. P.106 for multiplier. */
344 /* In the previous version (see above), MSBs of the */
345 /* seed affect only MSBs of the array mt[]. */
348 for (rand->mti=1; rand->mti<N; rand->mti++)
349 rand->mt[rand->mti] = 1812433253UL *
350 (rand->mt[rand->mti-1] ^ (rand->mt[rand->mti-1] >> 30)) + rand->mti;
353 g_assert_not_reached ();
358 * g_rand_set_seed_array:
360 * @seed: array to initialize with
361 * @seed_length: length of array
363 * Initializes the random number generator by an array of longs.
364 * Array can be of arbitrary size, though only the first 624 values
365 * are taken. This function is useful if you have many low entropy
366 * seeds, or if you require more then 32 bits of actual entropy for
372 g_rand_set_seed_array (GRand *rand,
378 g_return_if_fail (rand != NULL);
379 g_return_if_fail (seed_length >= 1);
381 g_rand_set_seed (rand, 19650218UL);
384 k = (N>seed_length ? N : seed_length);
387 rand->mt[i] = (rand->mt[i] ^
388 ((rand->mt[i-1] ^ (rand->mt[i-1] >> 30)) * 1664525UL))
389 + seed[j] + j; /* non linear */
390 rand->mt[i] &= 0xffffffffUL; /* for WORDSIZE > 32 machines */
394 rand->mt[0] = rand->mt[N-1];
402 rand->mt[i] = (rand->mt[i] ^
403 ((rand->mt[i-1] ^ (rand->mt[i-1] >> 30)) * 1566083941UL))
404 - i; /* non linear */
405 rand->mt[i] &= 0xffffffffUL; /* for WORDSIZE > 32 machines */
409 rand->mt[0] = rand->mt[N-1];
414 rand->mt[0] = 0x80000000UL; /* MSB is 1; assuring non-zero initial array */
421 * Returns a random #gboolean from @rand_.
422 * This corresponds to a unbiased coin toss.
424 * Returns: a random #gboolean
430 * Returns the next random #guint32 from @rand_ equally distributed over
431 * the range [0..2^32-1].
433 * Return value: a random number
436 g_rand_int (GRand *rand)
439 static const guint32 mag01[2]={0x0, MATRIX_A};
440 /* mag01[x] = x * MATRIX_A for x=0,1 */
442 g_return_val_if_fail (rand != NULL, 0);
444 if (rand->mti >= N) { /* generate N words at one time */
447 for (kk = 0; kk < N - M; kk++) {
448 y = (rand->mt[kk]&UPPER_MASK)|(rand->mt[kk+1]&LOWER_MASK);
449 rand->mt[kk] = rand->mt[kk+M] ^ (y >> 1) ^ mag01[y & 0x1];
451 for (; kk < N - 1; kk++) {
452 y = (rand->mt[kk]&UPPER_MASK)|(rand->mt[kk+1]&LOWER_MASK);
453 rand->mt[kk] = rand->mt[kk+(M-N)] ^ (y >> 1) ^ mag01[y & 0x1];
455 y = (rand->mt[N-1]&UPPER_MASK)|(rand->mt[0]&LOWER_MASK);
456 rand->mt[N-1] = rand->mt[M-1] ^ (y >> 1) ^ mag01[y & 0x1];
461 y = rand->mt[rand->mti++];
462 y ^= TEMPERING_SHIFT_U(y);
463 y ^= TEMPERING_SHIFT_S(y) & TEMPERING_MASK_B;
464 y ^= TEMPERING_SHIFT_T(y) & TEMPERING_MASK_C;
465 y ^= TEMPERING_SHIFT_L(y);
470 /* transform [0..2^32] -> [0..1] */
471 #define G_RAND_DOUBLE_TRANSFORM 2.3283064365386962890625e-10
476 * @begin: lower closed bound of the interval
477 * @end: upper open bound of the interval
479 * Returns the next random #gint32 from @rand_ equally distributed over
480 * the range [@begin..@end-1].
482 * Return value: a random number
485 g_rand_int_range (GRand *rand,
489 guint32 dist = end - begin;
492 g_return_val_if_fail (rand != NULL, begin);
493 g_return_val_if_fail (end > begin, begin);
495 switch (get_random_version ())
498 if (dist <= 0x10000L) /* 2^16 */
500 /* This method, which only calls g_rand_int once is only good
501 * for (end - begin) <= 2^16, because we only have 32 bits set
502 * from the one call to g_rand_int ().
504 * We are using (trans + trans * trans), because g_rand_int only
505 * covers [0..2^32-1] and thus g_rand_int * trans only covers
506 * [0..1-2^-32], but the biggest double < 1 is 1-2^-52.
509 gdouble double_rand = g_rand_int (rand) *
510 (G_RAND_DOUBLE_TRANSFORM +
511 G_RAND_DOUBLE_TRANSFORM * G_RAND_DOUBLE_TRANSFORM);
513 random = (gint32) (double_rand * dist);
517 /* Now we use g_rand_double_range (), which will set 52 bits
518 * for us, so that it is safe to round and still get a decent
521 random = (gint32) g_rand_double_range (rand, 0, dist);
529 /* maxvalue is set to the predecessor of the greatest
530 * multiple of dist less or equal 2^32.
533 if (dist <= 0x80000000u) /* 2^31 */
535 /* maxvalue = 2^32 - 1 - (2^32 % dist) */
536 guint32 leftover = (0x80000000u % dist) * 2;
537 if (leftover >= dist) leftover -= dist;
538 maxvalue = 0xffffffffu - leftover;
544 random = g_rand_int (rand);
545 while (random > maxvalue);
551 random = 0; /* Quiet GCC */
552 g_assert_not_reached ();
555 return begin + random;
562 * Returns the next random #gdouble from @rand_ equally distributed over
565 * Return value: a random number
568 g_rand_double (GRand *rand)
570 /* We set all 52 bits after the point for this, not only the first
571 32. Thats why we need two calls to g_rand_int */
572 gdouble retval = g_rand_int (rand) * G_RAND_DOUBLE_TRANSFORM;
573 retval = (retval + g_rand_int (rand)) * G_RAND_DOUBLE_TRANSFORM;
575 /* The following might happen due to very bad rounding luck, but
576 * actually this should be more than rare, we just try again then */
578 return g_rand_double (rand);
584 * g_rand_double_range:
586 * @begin: lower closed bound of the interval
587 * @end: upper open bound of the interval
589 * Returns the next random #gdouble from @rand_ equally distributed over
590 * the range [@begin..@end).
592 * Return value: a random number
595 g_rand_double_range (GRand *rand,
601 r = g_rand_double (rand);
603 return r * end - (r - 1) * begin;
607 get_global_random (void)
609 static GRand *global_random;
611 /* called while locked */
613 global_random = g_rand_new ();
615 return global_random;
621 * Returns a random #gboolean.
622 * This corresponds to a unbiased coin toss.
624 * Returns: a random #gboolean
629 * Return a random #guint32 equally distributed over the range
632 * Return value: a random number
638 G_LOCK (global_random);
639 result = g_rand_int (get_global_random ());
640 G_UNLOCK (global_random);
645 * g_random_int_range:
646 * @begin: lower closed bound of the interval
647 * @end: upper open bound of the interval
649 * Returns a random #gint32 equally distributed over the range
652 * Return value: a random number
655 g_random_int_range (gint32 begin,
659 G_LOCK (global_random);
660 result = g_rand_int_range (get_global_random (), begin, end);
661 G_UNLOCK (global_random);
668 * Returns a random #gdouble equally distributed over the range [0..1).
670 * Return value: a random number
673 g_random_double (void)
676 G_LOCK (global_random);
677 result = g_rand_double (get_global_random ());
678 G_UNLOCK (global_random);
683 * g_random_double_range:
684 * @begin: lower closed bound of the interval
685 * @end: upper open bound of the interval
687 * Returns a random #gdouble equally distributed over the range
690 * Return value: a random number
693 g_random_double_range (gdouble begin,
697 G_LOCK (global_random);
698 result = g_rand_double_range (get_global_random (), begin, end);
699 G_UNLOCK (global_random);
705 * @seed: a value to reinitialize the global random number generator
707 * Sets the seed for the global random number generator, which is used
708 * by the g_random_* functions, to @seed.
711 g_random_set_seed (guint32 seed)
713 G_LOCK (global_random);
714 g_rand_set_seed (get_global_random (), seed);
715 G_UNLOCK (global_random);