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, write to the
16 * Free Software Foundation, Inc., 59 Temple Place - Suite 330,
17 * Boston, MA 02111-1307, USA.
20 /* Originally developed and coded by Makoto Matsumoto and Takuji
21 * Nishimura. Please mail <matumoto@math.keio.ac.jp>, if you're using
22 * code from this file in your own programs or libraries.
23 * Further information on the Mersenne Twister can be found at
24 * http://www.math.sci.hiroshima-u.ac.jp/~m-mat/MT/emt.html
25 * This code was adapted to glib by Sebastian Wilhelmi.
29 * Modified by the GLib Team and others 1997-2000. See the AUTHORS
30 * file for a list of people on the GLib Team. See the ChangeLog
31 * files for a list of changes. These files are distributed with
32 * GLib at ftp://ftp.gtk.org/pub/gtk/.
46 #include <sys/types.h>
56 #include "gtestutils.h"
64 * SECTION:random_numbers
65 * @title: Random Numbers
66 * @short_description: pseudo-random number generator
68 * The following functions allow you to use a portable, fast and good
69 * pseudo-random number generator (PRNG).
71 * <warning><para>Do not use this API for cryptographic purposes such as key
72 * generation, nonces, salts or one-time pads.</para></warning>
74 * This PRNG is suitable for non-cryptographic use such as in games
75 * (shuffling a card deck, generating levels), generating data for a
76 * test suite, etc. If you need random data for cryptographic
77 * purposes, it is recommended to use platform-specific APIs such as
78 * <literal>/dev/random</literal> on Unix, or CryptGenRandom() on
81 * GRand uses the Mersenne Twister PRNG, which was originally
82 * developed by Makoto Matsumoto and Takuji Nishimura. Further
83 * information can be found at <ulink
84 * url="http://www.math.sci.hiroshima-u.ac.jp/~m-mat/MT/emt.html">
85 * http://www.math.sci.hiroshima-u.ac.jp/~m-mat/MT/emt.html</ulink>.
87 * If you just need a random number, you simply call the
88 * <function>g_random_*</function> functions, which will create a
89 * globally used #GRand and use the according
90 * <function>g_rand_*</function> functions internally. Whenever you
91 * need a stream of reproducible random numbers, you better create a
92 * #GRand yourself and use the <function>g_rand_*</function> functions
93 * directly, which will also be slightly faster. Initializing a #GRand
94 * with a certain seed will produce exactly the same series of random
95 * numbers on all platforms. This can thus be used as a seed for e.g.
98 * The <function>g_rand*_range</function> functions will return high
99 * quality equally distributed random numbers, whereas for example the
100 * <literal>(g_random_int()%max)</literal> approach often
101 * doesn't yield equally distributed numbers.
103 * GLib changed the seeding algorithm for the pseudo-random number
104 * generator Mersenne Twister, as used by
105 * <structname>GRand</structname> and <structname>GRandom</structname>.
106 * This was necessary, because some seeds would yield very bad
107 * pseudo-random streams. Also the pseudo-random integers generated by
108 * <function>g_rand*_int_range()</function> will have a slightly better
109 * equal distribution with the new version of GLib.
111 * The original seeding and generation algorithms, as found in GLib
112 * 2.0.x, can be used instead of the new ones by setting the
113 * environment variable <envar>G_RANDOM_VERSION</envar> to the value of
114 * '2.0'. Use the GLib-2.0 algorithms only if you have sequences of
115 * numbers generated with Glib-2.0 that you need to reproduce exactly.
121 * The #GRand struct is an opaque data structure. It should only be
122 * accessed through the <function>g_rand_*</function> functions.
125 G_LOCK_DEFINE_STATIC (global_random);
126 static GRand* global_random = NULL;
128 /* Period parameters */
131 #define MATRIX_A 0x9908b0df /* constant vector a */
132 #define UPPER_MASK 0x80000000 /* most significant w-r bits */
133 #define LOWER_MASK 0x7fffffff /* least significant r bits */
135 /* Tempering parameters */
136 #define TEMPERING_MASK_B 0x9d2c5680
137 #define TEMPERING_MASK_C 0xefc60000
138 #define TEMPERING_SHIFT_U(y) (y >> 11)
139 #define TEMPERING_SHIFT_S(y) (y << 7)
140 #define TEMPERING_SHIFT_T(y) (y << 15)
141 #define TEMPERING_SHIFT_L(y) (y >> 18)
144 get_random_version (void)
146 static gsize initialized = FALSE;
147 static guint random_version;
149 if (g_once_init_enter (&initialized))
151 const gchar *version_string = g_getenv ("G_RANDOM_VERSION");
152 if (!version_string || version_string[0] == '\000' ||
153 strcmp (version_string, "2.2") == 0)
155 else if (strcmp (version_string, "2.0") == 0)
159 g_warning ("Unknown G_RANDOM_VERSION \"%s\". Using version 2.2.",
163 g_once_init_leave (&initialized, TRUE);
166 return random_version;
171 guint32 mt[N]; /* the array for the state vector */
176 * g_rand_new_with_seed:
177 * @seed: a value to initialize the random number generator.
179 * Creates a new random number generator initialized with @seed.
181 * Return value: the new #GRand.
184 g_rand_new_with_seed (guint32 seed)
186 GRand *rand = g_new0 (GRand, 1);
187 g_rand_set_seed (rand, seed);
192 * g_rand_new_with_seed_array:
193 * @seed: an array of seeds to initialize the random number generator.
194 * @seed_length: an array of seeds to initialize the random number generator.
196 * Creates a new random number generator initialized with @seed.
198 * Return value: the new #GRand.
203 g_rand_new_with_seed_array (const guint32 *seed, guint seed_length)
205 GRand *rand = g_new0 (GRand, 1);
206 g_rand_set_seed_array (rand, seed, seed_length);
213 * Creates a new random number generator initialized with a seed taken
214 * either from <filename>/dev/urandom</filename> (if existing) or from
215 * the current time (as a fallback). On Windows, the seed is taken from
218 * Return value: the new #GRand.
225 static gboolean dev_urandom_exists = TRUE;
228 if (dev_urandom_exists)
234 dev_urandom = fopen("/dev/urandom", "rb");
236 while G_UNLIKELY (dev_urandom == NULL && errno == EINTR);
242 setvbuf (dev_urandom, NULL, _IONBF, 0);
246 r = fread (seed, sizeof (seed), 1, dev_urandom);
248 while G_UNLIKELY (errno == EINTR);
251 dev_urandom_exists = FALSE;
253 fclose (dev_urandom);
256 dev_urandom_exists = FALSE;
259 if (!dev_urandom_exists)
261 g_get_current_time (&now);
262 seed[0] = now.tv_sec;
263 seed[1] = now.tv_usec;
265 seed[3] = getppid ();
267 #else /* G_OS_WIN32 */
270 for (i = 0; i < G_N_ELEMENTS (seed); i++)
274 return g_rand_new_with_seed_array (seed, 4);
281 * Frees the memory allocated for the #GRand.
284 g_rand_free (GRand* rand)
286 g_return_if_fail (rand != NULL);
295 * Copies a #GRand into a new one with the same exact state as before.
296 * This way you can take a snapshot of the random number generator for
299 * Return value: the new #GRand.
304 g_rand_copy (GRand* rand)
308 g_return_val_if_fail (rand != NULL, NULL);
310 new_rand = g_new0 (GRand, 1);
311 memcpy (new_rand, rand, sizeof (GRand));
319 * @seed: a value to reinitialize the random number generator.
321 * Sets the seed for the random number generator #GRand to @seed.
324 g_rand_set_seed (GRand* rand, guint32 seed)
326 g_return_if_fail (rand != NULL);
328 switch (get_random_version ())
331 /* setting initial seeds to mt[N] using */
332 /* the generator Line 25 of Table 1 in */
333 /* [KNUTH 1981, The Art of Computer Programming */
334 /* Vol. 2 (2nd Ed.), pp102] */
336 if (seed == 0) /* This would make the PRNG produce only zeros */
337 seed = 0x6b842128; /* Just set it to another number */
340 for (rand->mti=1; rand->mti<N; rand->mti++)
341 rand->mt[rand->mti] = (69069 * rand->mt[rand->mti-1]);
345 /* See Knuth TAOCP Vol2. 3rd Ed. P.106 for multiplier. */
346 /* In the previous version (see above), MSBs of the */
347 /* seed affect only MSBs of the array mt[]. */
350 for (rand->mti=1; rand->mti<N; rand->mti++)
351 rand->mt[rand->mti] = 1812433253UL *
352 (rand->mt[rand->mti-1] ^ (rand->mt[rand->mti-1] >> 30)) + rand->mti;
355 g_assert_not_reached ();
360 * g_rand_set_seed_array:
362 * @seed: array to initialize with
363 * @seed_length: length of array
365 * Initializes the random number generator by an array of
366 * longs. Array can be of arbitrary size, though only the
367 * first 624 values are taken. This function is useful
368 * if you have many low entropy seeds, or if you require more then
369 * 32bits of actual entropy for your application.
374 g_rand_set_seed_array (GRand* rand, const guint32 *seed, guint seed_length)
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_. This corresponds to a
422 * 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];
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, gint32 begin, gint32 end)
487 guint32 dist = end - begin;
490 g_return_val_if_fail (rand != NULL, begin);
491 g_return_val_if_fail (end > begin, begin);
493 switch (get_random_version ())
496 if (dist <= 0x10000L) /* 2^16 */
498 /* This method, which only calls g_rand_int once is only good
499 * for (end - begin) <= 2^16, because we only have 32 bits set
500 * from the one call to g_rand_int (). */
502 /* we are using (trans + trans * trans), because g_rand_int only
503 * covers [0..2^32-1] and thus g_rand_int * trans only covers
504 * [0..1-2^-32], but the biggest double < 1 is 1-2^-52.
507 gdouble double_rand = g_rand_int (rand) *
508 (G_RAND_DOUBLE_TRANSFORM +
509 G_RAND_DOUBLE_TRANSFORM * G_RAND_DOUBLE_TRANSFORM);
511 random = (gint32) (double_rand * dist);
515 /* Now we use g_rand_double_range (), which will set 52 bits for
516 us, so that it is safe to round and still get a decent
518 random = (gint32) g_rand_double_range (rand, 0, dist);
526 /* maxvalue is set to the predecessor of the greatest
527 * multiple of dist less or equal 2^32. */
529 if (dist <= 0x80000000u) /* 2^31 */
531 /* maxvalue = 2^32 - 1 - (2^32 % dist) */
532 guint32 leftover = (0x80000000u % dist) * 2;
533 if (leftover >= dist) leftover -= dist;
534 maxvalue = 0xffffffffu - leftover;
540 random = g_rand_int (rand);
541 while (random > maxvalue);
547 random = 0; /* Quiet GCC */
548 g_assert_not_reached ();
551 return begin + random;
558 * Returns the next random #gdouble from @rand_ equally distributed over
561 * Return value: A random number.
564 g_rand_double (GRand* rand)
566 /* We set all 52 bits after the point for this, not only the first
567 32. Thats why we need two calls to g_rand_int */
568 gdouble retval = g_rand_int (rand) * G_RAND_DOUBLE_TRANSFORM;
569 retval = (retval + g_rand_int (rand)) * G_RAND_DOUBLE_TRANSFORM;
571 /* The following might happen due to very bad rounding luck, but
572 * actually this should be more than rare, we just try again then */
574 return g_rand_double (rand);
580 * g_rand_double_range:
582 * @begin: lower closed bound of the interval.
583 * @end: upper open bound of the interval.
585 * Returns the next random #gdouble from @rand_ equally distributed over
586 * the range [@begin..@end).
588 * Return value: A random number.
591 g_rand_double_range (GRand* rand, gdouble begin, gdouble end)
595 r = g_rand_double (rand);
597 return r * end - (r - 1) * begin;
603 * Returns a random #gboolean. This corresponds to a unbiased coin toss.
605 * Returns: a random #gboolean.
610 * Return a random #guint32 equally distributed over the range
613 * Return value: A random number.
619 G_LOCK (global_random);
621 global_random = g_rand_new ();
623 result = g_rand_int (global_random);
624 G_UNLOCK (global_random);
629 * g_random_int_range:
630 * @begin: lower closed bound of the interval.
631 * @end: upper open bound of the interval.
633 * Returns a random #gint32 equally distributed over the range
636 * Return value: A random number.
639 g_random_int_range (gint32 begin, gint32 end)
642 G_LOCK (global_random);
644 global_random = g_rand_new ();
646 result = g_rand_int_range (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);
664 global_random = g_rand_new ();
666 result = g_rand_double (global_random);
667 G_UNLOCK (global_random);
672 * g_random_double_range:
673 * @begin: lower closed bound of the interval.
674 * @end: upper open bound of the interval.
676 * Returns a random #gdouble equally distributed over the range [@begin..@end).
678 * Return value: A random number.
681 g_random_double_range (gdouble begin, gdouble end)
684 G_LOCK (global_random);
686 global_random = g_rand_new ();
688 result = g_rand_double_range (global_random, begin, end);
689 G_UNLOCK (global_random);
695 * @seed: a value to reinitialize the global random number generator.
697 * Sets the seed for the global random number generator, which is used
698 * by the <function>g_random_*</function> functions, to @seed.
701 g_random_set_seed (guint32 seed)
703 G_LOCK (global_random);
705 global_random = g_rand_new_with_seed (seed);
707 g_rand_set_seed (global_random, seed);
708 G_UNLOCK (global_random);