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
74 * a test suite, etc. If you need random data for cryptographic
75 * purposes, it is recommended to use platform-specific APIs such
76 * as `/dev/random` on UNIX, or CryptGenRandom() on Windows.
78 * GRand uses the Mersenne Twister PRNG, which was originally
79 * developed by Makoto Matsumoto and Takuji Nishimura. Further
80 * information can be found at
81 * [this page](http://www.math.sci.hiroshima-u.ac.jp/~m-mat/MT/emt.html).
83 * If you just need a random number, you simply call the g_random_*
84 * functions, which will create a globally used #GRand and use the
85 * according g_rand_* functions internally. Whenever you need a
86 * stream of reproducible random numbers, you better create a
87 * #GRand yourself and use the g_rand_* functions directly, which
88 * will also be slightly faster. Initializing a #GRand with a
89 * certain seed will produce exactly the same series of random
90 * numbers on all platforms. This can thus be used as a seed for
93 * The g_rand*_range functions will return high quality equally
94 * distributed random numbers, whereas for example the
95 * `(g_random_int()%max)` approach often
96 * doesn't yield equally distributed numbers.
98 * GLib changed the seeding algorithm for the pseudo-random number
99 * generator Mersenne Twister, as used by #GRand. This was necessary,
100 * because some seeds would yield very bad pseudo-random streams.
101 * Also the pseudo-random integers generated by g_rand*_int_range()
102 * will have a slightly better equal distribution with the new
105 * The original seeding and generation algorithms, as found in
106 * GLib 2.0.x, can be used instead of the new ones by setting the
107 * environment variable `G_RANDOM_VERSION` to the value of '2.0'.
108 * Use the GLib-2.0 algorithms only if you have sequences of numbers
109 * generated with Glib-2.0 that you need to reproduce exactly.
115 * The GRand struct is an opaque data structure. It should only be
116 * accessed through the g_rand_* functions.
119 G_LOCK_DEFINE_STATIC (global_random);
121 /* Period parameters */
124 #define MATRIX_A 0x9908b0df /* constant vector a */
125 #define UPPER_MASK 0x80000000 /* most significant w-r bits */
126 #define LOWER_MASK 0x7fffffff /* least significant r bits */
128 /* Tempering parameters */
129 #define TEMPERING_MASK_B 0x9d2c5680
130 #define TEMPERING_MASK_C 0xefc60000
131 #define TEMPERING_SHIFT_U(y) (y >> 11)
132 #define TEMPERING_SHIFT_S(y) (y << 7)
133 #define TEMPERING_SHIFT_T(y) (y << 15)
134 #define TEMPERING_SHIFT_L(y) (y >> 18)
137 get_random_version (void)
139 static gsize initialized = FALSE;
140 static guint random_version;
142 if (g_once_init_enter (&initialized))
144 const gchar *version_string = g_getenv ("G_RANDOM_VERSION");
145 if (!version_string || version_string[0] == '\000' ||
146 strcmp (version_string, "2.2") == 0)
148 else if (strcmp (version_string, "2.0") == 0)
152 g_warning ("Unknown G_RANDOM_VERSION \"%s\". Using version 2.2.",
156 g_once_init_leave (&initialized, TRUE);
159 return random_version;
164 guint32 mt[N]; /* the array for the state vector */
169 * g_rand_new_with_seed:
170 * @seed: a value to initialize the random number generator
172 * Creates a new random number generator initialized with @seed.
174 * Returns: the new #GRand
177 g_rand_new_with_seed (guint32 seed)
179 GRand *rand = g_new0 (GRand, 1);
180 g_rand_set_seed (rand, seed);
185 * g_rand_new_with_seed_array:
186 * @seed: an array of seeds to initialize the random number generator
187 * @seed_length: an array of seeds to initialize the random number
190 * Creates a new random number generator initialized with @seed.
192 * Returns: the new #GRand
197 g_rand_new_with_seed_array (const guint32 *seed,
200 GRand *rand = g_new0 (GRand, 1);
201 g_rand_set_seed_array (rand, seed, seed_length);
208 * Creates a new random number generator initialized with a seed taken
209 * either from `/dev/urandom` (if existing) or from the current time
212 * On Windows, the seed is taken from rand_s().
214 * Returns: the new #GRand
221 static gboolean dev_urandom_exists = TRUE;
224 if (dev_urandom_exists)
230 dev_urandom = fopen("/dev/urandom", "rb");
232 while G_UNLIKELY (dev_urandom == NULL && errno == EINTR);
238 setvbuf (dev_urandom, NULL, _IONBF, 0);
242 r = fread (seed, sizeof (seed), 1, dev_urandom);
244 while G_UNLIKELY (errno == EINTR);
247 dev_urandom_exists = FALSE;
249 fclose (dev_urandom);
252 dev_urandom_exists = FALSE;
255 if (!dev_urandom_exists)
257 g_get_current_time (&now);
258 seed[0] = now.tv_sec;
259 seed[1] = now.tv_usec;
261 seed[3] = getppid ();
263 #else /* G_OS_WIN32 */
266 for (i = 0; i < G_N_ELEMENTS (seed); i++)
270 return g_rand_new_with_seed_array (seed, 4);
277 * Frees the memory allocated for the #GRand.
280 g_rand_free (GRand *rand)
282 g_return_if_fail (rand != NULL);
291 * Copies a #GRand into a new one with the same exact state as before.
292 * This way you can take a snapshot of the random number generator for
295 * Returns: the new #GRand
300 g_rand_copy (GRand *rand)
304 g_return_val_if_fail (rand != NULL, NULL);
306 new_rand = g_new0 (GRand, 1);
307 memcpy (new_rand, rand, sizeof (GRand));
315 * @seed: a value to reinitialize the random number generator
317 * Sets the seed for the random number generator #GRand to @seed.
320 g_rand_set_seed (GRand *rand,
323 g_return_if_fail (rand != NULL);
325 switch (get_random_version ())
328 /* setting initial seeds to mt[N] using */
329 /* the generator Line 25 of Table 1 in */
330 /* [KNUTH 1981, The Art of Computer Programming */
331 /* Vol. 2 (2nd Ed.), pp102] */
333 if (seed == 0) /* This would make the PRNG produce only zeros */
334 seed = 0x6b842128; /* Just set it to another number */
337 for (rand->mti=1; rand->mti<N; rand->mti++)
338 rand->mt[rand->mti] = (69069 * rand->mt[rand->mti-1]);
342 /* See Knuth TAOCP Vol2. 3rd Ed. P.106 for multiplier. */
343 /* In the previous version (see above), MSBs of the */
344 /* seed affect only MSBs of the array mt[]. */
347 for (rand->mti=1; rand->mti<N; rand->mti++)
348 rand->mt[rand->mti] = 1812433253UL *
349 (rand->mt[rand->mti-1] ^ (rand->mt[rand->mti-1] >> 30)) + rand->mti;
352 g_assert_not_reached ();
357 * g_rand_set_seed_array:
359 * @seed: array to initialize with
360 * @seed_length: length of array
362 * Initializes the random number generator by an array of longs.
363 * Array can be of arbitrary size, though only the first 624 values
364 * are taken. This function is useful if you have many low entropy
365 * seeds, or if you require more then 32 bits of actual entropy for
371 g_rand_set_seed_array (GRand *rand,
377 g_return_if_fail (rand != NULL);
378 g_return_if_fail (seed_length >= 1);
380 g_rand_set_seed (rand, 19650218UL);
383 k = (N>seed_length ? N : seed_length);
386 rand->mt[i] = (rand->mt[i] ^
387 ((rand->mt[i-1] ^ (rand->mt[i-1] >> 30)) * 1664525UL))
388 + seed[j] + j; /* non linear */
389 rand->mt[i] &= 0xffffffffUL; /* for WORDSIZE > 32 machines */
393 rand->mt[0] = rand->mt[N-1];
401 rand->mt[i] = (rand->mt[i] ^
402 ((rand->mt[i-1] ^ (rand->mt[i-1] >> 30)) * 1566083941UL))
403 - i; /* non linear */
404 rand->mt[i] &= 0xffffffffUL; /* for WORDSIZE > 32 machines */
408 rand->mt[0] = rand->mt[N-1];
413 rand->mt[0] = 0x80000000UL; /* MSB is 1; assuring non-zero initial array */
420 * Returns a random #gboolean from @rand_.
421 * This corresponds to a unbiased coin toss.
423 * Returns: a random #gboolean
429 * Returns the next random #guint32 from @rand_ equally distributed over
430 * the range [0..2^32-1].
432 * Returns: a random number
435 g_rand_int (GRand *rand)
438 static const guint32 mag01[2]={0x0, MATRIX_A};
439 /* mag01[x] = x * MATRIX_A for x=0,1 */
441 g_return_val_if_fail (rand != NULL, 0);
443 if (rand->mti >= N) { /* generate N words at one time */
446 for (kk = 0; kk < N - M; kk++) {
447 y = (rand->mt[kk]&UPPER_MASK)|(rand->mt[kk+1]&LOWER_MASK);
448 rand->mt[kk] = rand->mt[kk+M] ^ (y >> 1) ^ mag01[y & 0x1];
450 for (; kk < N - 1; kk++) {
451 y = (rand->mt[kk]&UPPER_MASK)|(rand->mt[kk+1]&LOWER_MASK);
452 rand->mt[kk] = rand->mt[kk+(M-N)] ^ (y >> 1) ^ mag01[y & 0x1];
454 y = (rand->mt[N-1]&UPPER_MASK)|(rand->mt[0]&LOWER_MASK);
455 rand->mt[N-1] = rand->mt[M-1] ^ (y >> 1) ^ mag01[y & 0x1];
460 y = rand->mt[rand->mti++];
461 y ^= TEMPERING_SHIFT_U(y);
462 y ^= TEMPERING_SHIFT_S(y) & TEMPERING_MASK_B;
463 y ^= TEMPERING_SHIFT_T(y) & TEMPERING_MASK_C;
464 y ^= TEMPERING_SHIFT_L(y);
469 /* transform [0..2^32] -> [0..1] */
470 #define G_RAND_DOUBLE_TRANSFORM 2.3283064365386962890625e-10
475 * @begin: lower closed bound of the interval
476 * @end: upper open bound of the interval
478 * Returns the next random #gint32 from @rand_ equally distributed over
479 * the range [@begin..@end-1].
481 * Returns: a random number
484 g_rand_int_range (GRand *rand,
488 guint32 dist = end - begin;
491 g_return_val_if_fail (rand != NULL, begin);
492 g_return_val_if_fail (end > begin, begin);
494 switch (get_random_version ())
497 if (dist <= 0x10000L) /* 2^16 */
499 /* This method, which only calls g_rand_int once is only good
500 * for (end - begin) <= 2^16, because we only have 32 bits set
501 * from the one call to g_rand_int ().
503 * We are using (trans + trans * trans), because g_rand_int only
504 * covers [0..2^32-1] and thus g_rand_int * trans only covers
505 * [0..1-2^-32], but the biggest double < 1 is 1-2^-52.
508 gdouble double_rand = g_rand_int (rand) *
509 (G_RAND_DOUBLE_TRANSFORM +
510 G_RAND_DOUBLE_TRANSFORM * G_RAND_DOUBLE_TRANSFORM);
512 random = (gint32) (double_rand * dist);
516 /* Now we use g_rand_double_range (), which will set 52 bits
517 * for us, so that it is safe to round and still get a decent
520 random = (gint32) g_rand_double_range (rand, 0, dist);
528 /* maxvalue is set to the predecessor of the greatest
529 * multiple of dist less or equal 2^32.
532 if (dist <= 0x80000000u) /* 2^31 */
534 /* maxvalue = 2^32 - 1 - (2^32 % dist) */
535 guint32 leftover = (0x80000000u % dist) * 2;
536 if (leftover >= dist) leftover -= dist;
537 maxvalue = 0xffffffffu - leftover;
543 random = g_rand_int (rand);
544 while (random > maxvalue);
550 random = 0; /* Quiet GCC */
551 g_assert_not_reached ();
554 return begin + random;
561 * Returns the next random #gdouble from @rand_ equally distributed over
564 * Returns: a random number
567 g_rand_double (GRand *rand)
569 /* We set all 52 bits after the point for this, not only the first
570 32. Thats why we need two calls to g_rand_int */
571 gdouble retval = g_rand_int (rand) * G_RAND_DOUBLE_TRANSFORM;
572 retval = (retval + g_rand_int (rand)) * G_RAND_DOUBLE_TRANSFORM;
574 /* The following might happen due to very bad rounding luck, but
575 * actually this should be more than rare, we just try again then */
577 return g_rand_double (rand);
583 * g_rand_double_range:
585 * @begin: lower closed bound of the interval
586 * @end: upper open bound of the interval
588 * Returns the next random #gdouble from @rand_ equally distributed over
589 * the range [@begin..@end).
591 * Returns: a random number
594 g_rand_double_range (GRand *rand,
600 r = g_rand_double (rand);
602 return r * end - (r - 1) * begin;
606 get_global_random (void)
608 static GRand *global_random;
610 /* called while locked */
612 global_random = g_rand_new ();
614 return global_random;
620 * Returns a random #gboolean.
621 * This corresponds to a unbiased coin toss.
623 * Returns: a random #gboolean
628 * Return a random #guint32 equally distributed over the range
631 * Returns: a random number
637 G_LOCK (global_random);
638 result = g_rand_int (get_global_random ());
639 G_UNLOCK (global_random);
644 * g_random_int_range:
645 * @begin: lower closed bound of the interval
646 * @end: upper open bound of the interval
648 * Returns a random #gint32 equally distributed over the range
651 * Returns: a random number
654 g_random_int_range (gint32 begin,
658 G_LOCK (global_random);
659 result = g_rand_int_range (get_global_random (), begin, end);
660 G_UNLOCK (global_random);
667 * Returns a random #gdouble equally distributed over the range [0..1).
669 * Returns: a random number
672 g_random_double (void)
675 G_LOCK (global_random);
676 result = g_rand_double (get_global_random ());
677 G_UNLOCK (global_random);
682 * g_random_double_range:
683 * @begin: lower closed bound of the interval
684 * @end: upper open bound of the interval
686 * Returns a random #gdouble equally distributed over the range
689 * Returns: a random number
692 g_random_double_range (gdouble begin,
696 G_LOCK (global_random);
697 result = g_rand_double_range (get_global_random (), begin, end);
698 G_UNLOCK (global_random);
704 * @seed: a value to reinitialize the global random number generator
706 * Sets the seed for the global random number generator, which is used
707 * by the g_random_* functions, to @seed.
710 g_random_set_seed (guint32 seed)
712 G_LOCK (global_random);
713 g_rand_set_seed (get_global_random (), seed);
714 G_UNLOCK (global_random);