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 <ulink
82 * url="http://www.math.sci.hiroshima-u.ac.jp/~m-mat/MT/emt.html">
83 * http://www.math.sci.hiroshima-u.ac.jp/~m-mat/MT/emt.html</ulink>.
85 * If you just need a random number, you simply call the g_random_*
86 * functions, which will create a globally used #GRand and use the
87 * according g_rand_* functions internally. Whenever you
88 * need a stream of reproducible random numbers, you better create a
89 * #GRand yourself and use the g_rand_* functions directly, which will
90 * also be slightly faster. Initializing a #GRand with a certain seed
91 * will produce exactly the same series of random numbers on all
92 * platforms. This can thus be used as a seed for e.g. games.
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 and #GRandom.
101 * This was necessary, because some seeds would yield very bad
102 * pseudo-random streams. Also the pseudo-random integers generated
103 * by g_rand*_int_range() will have a slightly better equal
104 * distribution with the new version of GLib.
106 * The original seeding and generation algorithms, as found in GLib
107 * 2.0.x, can be used instead of the new ones by setting the
108 * environment variable <envar>G_RANDOM_VERSION</envar> to the value of
109 * '2.0'. Use the GLib-2.0 algorithms only if you have sequences of
110 * numbers 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 generator.
190 * Creates a new random number generator initialized with @seed.
192 * Return value: the new #GRand.
197 g_rand_new_with_seed_array (const guint32 *seed, guint seed_length)
199 GRand *rand = g_new0 (GRand, 1);
200 g_rand_set_seed_array (rand, seed, seed_length);
207 * Creates a new random number generator initialized with a seed taken
208 * either from <filename>/dev/urandom</filename> (if existing) or from
209 * the current time (as a fallback). On Windows, the seed is taken from
212 * Return value: the new #GRand.
219 static gboolean dev_urandom_exists = TRUE;
222 if (dev_urandom_exists)
228 dev_urandom = fopen("/dev/urandom", "rb");
230 while G_UNLIKELY (dev_urandom == NULL && errno == EINTR);
236 setvbuf (dev_urandom, NULL, _IONBF, 0);
240 r = fread (seed, sizeof (seed), 1, dev_urandom);
242 while G_UNLIKELY (errno == EINTR);
245 dev_urandom_exists = FALSE;
247 fclose (dev_urandom);
250 dev_urandom_exists = FALSE;
253 if (!dev_urandom_exists)
255 g_get_current_time (&now);
256 seed[0] = now.tv_sec;
257 seed[1] = now.tv_usec;
259 seed[3] = getppid ();
261 #else /* G_OS_WIN32 */
264 for (i = 0; i < G_N_ELEMENTS (seed); i++)
268 return g_rand_new_with_seed_array (seed, 4);
275 * Frees the memory allocated for the #GRand.
278 g_rand_free (GRand* rand)
280 g_return_if_fail (rand != NULL);
289 * Copies a #GRand into a new one with the same exact state as before.
290 * This way you can take a snapshot of the random number generator for
293 * Return value: the new #GRand.
298 g_rand_copy (GRand* rand)
302 g_return_val_if_fail (rand != NULL, NULL);
304 new_rand = g_new0 (GRand, 1);
305 memcpy (new_rand, rand, sizeof (GRand));
313 * @seed: a value to reinitialize the random number generator.
315 * Sets the seed for the random number generator #GRand to @seed.
318 g_rand_set_seed (GRand* rand, guint32 seed)
320 g_return_if_fail (rand != NULL);
322 switch (get_random_version ())
325 /* setting initial seeds to mt[N] using */
326 /* the generator Line 25 of Table 1 in */
327 /* [KNUTH 1981, The Art of Computer Programming */
328 /* Vol. 2 (2nd Ed.), pp102] */
330 if (seed == 0) /* This would make the PRNG produce only zeros */
331 seed = 0x6b842128; /* Just set it to another number */
334 for (rand->mti=1; rand->mti<N; rand->mti++)
335 rand->mt[rand->mti] = (69069 * rand->mt[rand->mti-1]);
339 /* See Knuth TAOCP Vol2. 3rd Ed. P.106 for multiplier. */
340 /* In the previous version (see above), MSBs of the */
341 /* seed affect only MSBs of the array mt[]. */
344 for (rand->mti=1; rand->mti<N; rand->mti++)
345 rand->mt[rand->mti] = 1812433253UL *
346 (rand->mt[rand->mti-1] ^ (rand->mt[rand->mti-1] >> 30)) + rand->mti;
349 g_assert_not_reached ();
354 * g_rand_set_seed_array:
356 * @seed: array to initialize with
357 * @seed_length: length of array
359 * Initializes the random number generator by an array of longs.
360 * Array can be of arbitrary size, though only the
361 * first 624 values are taken. This function is useful
362 * if you have many low entropy seeds, or if you require more then
363 * 32 bits of actual entropy for your application.
368 g_rand_set_seed_array (GRand* rand, const guint32 *seed, guint seed_length)
372 g_return_if_fail (rand != NULL);
373 g_return_if_fail (seed_length >= 1);
375 g_rand_set_seed (rand, 19650218UL);
378 k = (N>seed_length ? N : seed_length);
381 rand->mt[i] = (rand->mt[i] ^
382 ((rand->mt[i-1] ^ (rand->mt[i-1] >> 30)) * 1664525UL))
383 + seed[j] + j; /* non linear */
384 rand->mt[i] &= 0xffffffffUL; /* for WORDSIZE > 32 machines */
388 rand->mt[0] = rand->mt[N-1];
396 rand->mt[i] = (rand->mt[i] ^
397 ((rand->mt[i-1] ^ (rand->mt[i-1] >> 30)) * 1566083941UL))
398 - i; /* non linear */
399 rand->mt[i] &= 0xffffffffUL; /* for WORDSIZE > 32 machines */
403 rand->mt[0] = rand->mt[N-1];
408 rand->mt[0] = 0x80000000UL; /* MSB is 1; assuring non-zero initial array */
415 * Returns a random #gboolean from @rand_. This corresponds to a
416 * unbiased coin toss.
418 * Returns: a random #gboolean.
424 * Returns the next random #guint32 from @rand_ equally distributed over
425 * the range [0..2^32-1].
427 * Return value: A random number.
430 g_rand_int (GRand* rand)
433 static const guint32 mag01[2]={0x0, MATRIX_A};
434 /* mag01[x] = x * MATRIX_A for x=0,1 */
436 g_return_val_if_fail (rand != NULL, 0);
438 if (rand->mti >= N) { /* generate N words at one time */
441 for (kk=0;kk<N-M;kk++) {
442 y = (rand->mt[kk]&UPPER_MASK)|(rand->mt[kk+1]&LOWER_MASK);
443 rand->mt[kk] = rand->mt[kk+M] ^ (y >> 1) ^ mag01[y & 0x1];
446 y = (rand->mt[kk]&UPPER_MASK)|(rand->mt[kk+1]&LOWER_MASK);
447 rand->mt[kk] = rand->mt[kk+(M-N)] ^ (y >> 1) ^ mag01[y & 0x1];
449 y = (rand->mt[N-1]&UPPER_MASK)|(rand->mt[0]&LOWER_MASK);
450 rand->mt[N-1] = rand->mt[M-1] ^ (y >> 1) ^ mag01[y & 0x1];
455 y = rand->mt[rand->mti++];
456 y ^= TEMPERING_SHIFT_U(y);
457 y ^= TEMPERING_SHIFT_S(y) & TEMPERING_MASK_B;
458 y ^= TEMPERING_SHIFT_T(y) & TEMPERING_MASK_C;
459 y ^= TEMPERING_SHIFT_L(y);
464 /* transform [0..2^32] -> [0..1] */
465 #define G_RAND_DOUBLE_TRANSFORM 2.3283064365386962890625e-10
470 * @begin: lower closed bound of the interval.
471 * @end: upper open bound of the interval.
473 * Returns the next random #gint32 from @rand_ equally distributed over
474 * the range [@begin..@end-1].
476 * Return value: A random number.
479 g_rand_int_range (GRand* rand, gint32 begin, gint32 end)
481 guint32 dist = end - begin;
484 g_return_val_if_fail (rand != NULL, begin);
485 g_return_val_if_fail (end > begin, begin);
487 switch (get_random_version ())
490 if (dist <= 0x10000L) /* 2^16 */
492 /* This method, which only calls g_rand_int once is only good
493 * for (end - begin) <= 2^16, because we only have 32 bits set
494 * from the one call to g_rand_int (). */
496 /* we are using (trans + trans * trans), because g_rand_int only
497 * covers [0..2^32-1] and thus g_rand_int * trans only covers
498 * [0..1-2^-32], but the biggest double < 1 is 1-2^-52.
501 gdouble double_rand = g_rand_int (rand) *
502 (G_RAND_DOUBLE_TRANSFORM +
503 G_RAND_DOUBLE_TRANSFORM * G_RAND_DOUBLE_TRANSFORM);
505 random = (gint32) (double_rand * dist);
509 /* Now we use g_rand_double_range (), which will set 52 bits for
510 us, so that it is safe to round and still get a decent
512 random = (gint32) g_rand_double_range (rand, 0, dist);
520 /* maxvalue is set to the predecessor of the greatest
521 * multiple of dist less or equal 2^32. */
523 if (dist <= 0x80000000u) /* 2^31 */
525 /* maxvalue = 2^32 - 1 - (2^32 % dist) */
526 guint32 leftover = (0x80000000u % dist) * 2;
527 if (leftover >= dist) leftover -= dist;
528 maxvalue = 0xffffffffu - leftover;
534 random = g_rand_int (rand);
535 while (random > maxvalue);
541 random = 0; /* Quiet GCC */
542 g_assert_not_reached ();
545 return begin + random;
552 * Returns the next random #gdouble from @rand_ equally distributed over
555 * Return value: A random number.
558 g_rand_double (GRand* rand)
560 /* We set all 52 bits after the point for this, not only the first
561 32. Thats why we need two calls to g_rand_int */
562 gdouble retval = g_rand_int (rand) * G_RAND_DOUBLE_TRANSFORM;
563 retval = (retval + g_rand_int (rand)) * G_RAND_DOUBLE_TRANSFORM;
565 /* The following might happen due to very bad rounding luck, but
566 * actually this should be more than rare, we just try again then */
568 return g_rand_double (rand);
574 * g_rand_double_range:
576 * @begin: lower closed bound of the interval.
577 * @end: upper open bound of the interval.
579 * Returns the next random #gdouble from @rand_ equally distributed over
580 * the range [@begin..@end).
582 * Return value: A random number.
585 g_rand_double_range (GRand* rand, gdouble begin, gdouble end)
589 r = g_rand_double (rand);
591 return r * end - (r - 1) * begin;
595 get_global_random (void)
597 static GRand *global_random;
599 /* called while locked */
601 global_random = g_rand_new ();
603 return global_random;
609 * Returns a random #gboolean. This corresponds to a unbiased coin toss.
611 * Returns: a random #gboolean.
616 * Return a random #guint32 equally distributed over the range
619 * Return value: A random number.
625 G_LOCK (global_random);
626 result = g_rand_int (get_global_random ());
627 G_UNLOCK (global_random);
632 * g_random_int_range:
633 * @begin: lower closed bound of the interval.
634 * @end: upper open bound of the interval.
636 * Returns a random #gint32 equally distributed over the range
639 * Return value: A random number.
642 g_random_int_range (gint32 begin, gint32 end)
645 G_LOCK (global_random);
646 result = g_rand_int_range (get_global_random (), begin, end);
647 G_UNLOCK (global_random);
654 * Returns a random #gdouble equally distributed over the range [0..1).
656 * Return value: A random number.
659 g_random_double (void)
662 G_LOCK (global_random);
663 result = g_rand_double (get_global_random ());
664 G_UNLOCK (global_random);
669 * g_random_double_range:
670 * @begin: lower closed bound of the interval.
671 * @end: upper open bound of the interval.
673 * Returns a random #gdouble equally distributed over the range [@begin..@end).
675 * Return value: A random number.
678 g_random_double_range (gdouble begin, gdouble end)
681 G_LOCK (global_random);
682 result = g_rand_double_range (get_global_random (), begin, end);
683 G_UNLOCK (global_random);
689 * @seed: a value to reinitialize the global random number generator.
691 * Sets the seed for the global random number generator, which is used
692 * by the g_random_* functions, to @seed.
695 g_random_set_seed (guint32 seed)
697 G_LOCK (global_random);
698 g_rand_set_seed (get_global_random (), seed);
699 G_UNLOCK (global_random);