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/.
45 #include <sys/types.h>
55 #include "gtestutils.h"
59 #include <process.h> /* For getpid() */
63 * SECTION:random_numbers
64 * @title: Random Numbers
65 * @short_description: pseudo-random number generator
67 * The following functions allow you to use a portable, fast and good
68 * pseudo-random number generator (PRNG).
70 * <warning><para>Do not use this API for cryptographic purposes such as key
71 * generation, nonces, salts or one-time pads.</para></warning>
73 * This PRNG is suitable for non-cryptographic use such as in games
74 * (shuffling a card deck, generating levels), generating data for a
75 * test suite, etc. If you need random data for cryptographic
76 * purposes, it is recommended to use platform-specific APIs such as
77 * <literal>/dev/random</literal> on Unix, or CryptGenRandom() on
80 * GRand uses the Mersenne Twister PRNG, which was originally
81 * developed by Makoto Matsumoto and Takuji Nishimura. Further
82 * information can be found at <ulink
83 * url="http://www.math.sci.hiroshima-u.ac.jp/~m-mat/MT/emt.html">
84 * http://www.math.sci.hiroshima-u.ac.jp/~m-mat/MT/emt.html</ulink>.
86 * If you just need a random number, you simply call the
87 * <function>g_random_*</function> functions, which will create a
88 * globally used #GRand and use the according
89 * <function>g_rand_*</function> functions internally. Whenever you
90 * need a stream of reproducible random numbers, you better create a
91 * #GRand yourself and use the <function>g_rand_*</function> functions
92 * directly, which will also be slightly faster. Initializing a #GRand
93 * with a certain seed will produce exactly the same series of random
94 * numbers on all platforms. This can thus be used as a seed for e.g.
97 * The <function>g_rand*_range</function> functions will return high
98 * quality equally distributed random numbers, whereas for example the
99 * <literal>(g_random_int()%max)</literal> approach often
100 * doesn't yield equally distributed numbers.
102 * GLib changed the seeding algorithm for the pseudo-random number
103 * generator Mersenne Twister, as used by
104 * <structname>GRand</structname> and <structname>GRandom</structname>.
105 * This was necessary, because some seeds would yield very bad
106 * pseudo-random streams. Also the pseudo-random integers generated by
107 * <function>g_rand*_int_range()</function> will have a slightly better
108 * equal distribution with the new version of GLib.
110 * The original seeding and generation algorithms, as found in GLib
111 * 2.0.x, can be used instead of the new ones by setting the
112 * environment variable <envar>G_RANDOM_VERSION</envar> to the value of
113 * '2.0'. Use the GLib-2.0 algorithms only if you have sequences of
114 * numbers generated with Glib-2.0 that you need to reproduce exactly.
120 * The #GRand struct is an opaque data structure. It should only be
121 * accessed through the <function>g_rand_*</function> functions.
124 G_LOCK_DEFINE_STATIC (global_random);
125 static GRand* global_random = NULL;
127 /* Period parameters */
130 #define MATRIX_A 0x9908b0df /* constant vector a */
131 #define UPPER_MASK 0x80000000 /* most significant w-r bits */
132 #define LOWER_MASK 0x7fffffff /* least significant r bits */
134 /* Tempering parameters */
135 #define TEMPERING_MASK_B 0x9d2c5680
136 #define TEMPERING_MASK_C 0xefc60000
137 #define TEMPERING_SHIFT_U(y) (y >> 11)
138 #define TEMPERING_SHIFT_S(y) (y << 7)
139 #define TEMPERING_SHIFT_T(y) (y << 15)
140 #define TEMPERING_SHIFT_L(y) (y >> 18)
143 get_random_version (void)
145 static gsize initialized = FALSE;
146 static guint random_version;
148 if (g_once_init_enter (&initialized))
150 const gchar *version_string = g_getenv ("G_RANDOM_VERSION");
151 if (!version_string || version_string[0] == '\000' ||
152 strcmp (version_string, "2.2") == 0)
154 else if (strcmp (version_string, "2.0") == 0)
158 g_warning ("Unknown G_RANDOM_VERSION \"%s\". Using version 2.2.",
162 g_once_init_leave (&initialized, TRUE);
165 return random_version;
170 guint32 mt[N]; /* the array for the state vector */
175 * g_rand_new_with_seed:
176 * @seed: a value to initialize the random number generator.
178 * Creates a new random number generator initialized with @seed.
180 * Return value: the new #GRand.
183 g_rand_new_with_seed (guint32 seed)
185 GRand *rand = g_new0 (GRand, 1);
186 g_rand_set_seed (rand, seed);
191 * g_rand_new_with_seed_array:
192 * @seed: an array of seeds to initialize the random number generator.
193 * @seed_length: an array of seeds to initialize the random number generator.
195 * Creates a new random number generator initialized with @seed.
197 * Return value: the new #GRand.
202 g_rand_new_with_seed_array (const guint32 *seed, guint seed_length)
204 GRand *rand = g_new0 (GRand, 1);
205 g_rand_set_seed_array (rand, seed, seed_length);
212 * Creates a new random number generator initialized with a seed taken
213 * either from <filename>/dev/urandom</filename> (if existing) or from
214 * the current time (as a fallback).
216 * Return value: the new #GRand.
224 static gboolean dev_urandom_exists = TRUE;
226 if (dev_urandom_exists)
232 dev_urandom = fopen("/dev/urandom", "rb");
234 while G_UNLIKELY (dev_urandom == NULL && errno == EINTR);
240 setvbuf (dev_urandom, NULL, _IONBF, 0);
244 r = fread (seed, sizeof (seed), 1, dev_urandom);
246 while G_UNLIKELY (errno == EINTR);
249 dev_urandom_exists = FALSE;
251 fclose (dev_urandom);
254 dev_urandom_exists = FALSE;
257 static gboolean dev_urandom_exists = FALSE;
260 if (!dev_urandom_exists)
262 g_get_current_time (&now);
263 seed[0] = now.tv_sec;
264 seed[1] = now.tv_usec;
267 seed[3] = getppid ();
273 return g_rand_new_with_seed_array (seed, 4);
280 * Frees the memory allocated for the #GRand.
283 g_rand_free (GRand* rand)
285 g_return_if_fail (rand != NULL);
294 * Copies a #GRand into a new one with the same exact state as before.
295 * This way you can take a snapshot of the random number generator for
298 * Return value: the new #GRand.
303 g_rand_copy (GRand* rand)
307 g_return_val_if_fail (rand != NULL, NULL);
309 new_rand = g_new0 (GRand, 1);
310 memcpy (new_rand, rand, sizeof (GRand));
318 * @seed: a value to reinitialize the random number generator.
320 * Sets the seed for the random number generator #GRand to @seed.
323 g_rand_set_seed (GRand* rand, guint32 seed)
325 g_return_if_fail (rand != NULL);
327 switch (get_random_version ())
330 /* setting initial seeds to mt[N] using */
331 /* the generator Line 25 of Table 1 in */
332 /* [KNUTH 1981, The Art of Computer Programming */
333 /* Vol. 2 (2nd Ed.), pp102] */
335 if (seed == 0) /* This would make the PRNG produce only zeros */
336 seed = 0x6b842128; /* Just set it to another number */
339 for (rand->mti=1; rand->mti<N; rand->mti++)
340 rand->mt[rand->mti] = (69069 * rand->mt[rand->mti-1]);
344 /* See Knuth TAOCP Vol2. 3rd Ed. P.106 for multiplier. */
345 /* In the previous version (see above), MSBs of the */
346 /* seed affect only MSBs of the array mt[]. */
349 for (rand->mti=1; rand->mti<N; rand->mti++)
350 rand->mt[rand->mti] = 1812433253UL *
351 (rand->mt[rand->mti-1] ^ (rand->mt[rand->mti-1] >> 30)) + rand->mti;
354 g_assert_not_reached ();
359 * g_rand_set_seed_array:
361 * @seed: array to initialize with
362 * @seed_length: length of array
364 * Initializes the random number generator by an array of
365 * longs. Array can be of arbitrary size, though only the
366 * first 624 values are taken. This function is useful
367 * if you have many low entropy seeds, or if you require more then
368 * 32bits of actual entropy for your application.
373 g_rand_set_seed_array (GRand* rand, const guint32 *seed, guint seed_length)
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_. This corresponds to a
421 * 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 * Return value: 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];
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 * Return value: A random number.
484 g_rand_int_range (GRand* rand, gint32 begin, gint32 end)
486 guint32 dist = end - begin;
489 g_return_val_if_fail (rand != NULL, begin);
490 g_return_val_if_fail (end > begin, begin);
492 switch (get_random_version ())
495 if (dist <= 0x10000L) /* 2^16 */
497 /* This method, which only calls g_rand_int once is only good
498 * for (end - begin) <= 2^16, because we only have 32 bits set
499 * from the one call to g_rand_int (). */
501 /* we are using (trans + trans * trans), because g_rand_int only
502 * covers [0..2^32-1] and thus g_rand_int * trans only covers
503 * [0..1-2^-32], but the biggest double < 1 is 1-2^-52.
506 gdouble double_rand = g_rand_int (rand) *
507 (G_RAND_DOUBLE_TRANSFORM +
508 G_RAND_DOUBLE_TRANSFORM * G_RAND_DOUBLE_TRANSFORM);
510 random = (gint32) (double_rand * dist);
514 /* Now we use g_rand_double_range (), which will set 52 bits for
515 us, so that it is safe to round and still get a decent
517 random = (gint32) g_rand_double_range (rand, 0, dist);
525 /* maxvalue is set to the predecessor of the greatest
526 * multiple of dist less or equal 2^32. */
528 if (dist <= 0x80000000u) /* 2^31 */
530 /* maxvalue = 2^32 - 1 - (2^32 % dist) */
531 guint32 leftover = (0x80000000u % dist) * 2;
532 if (leftover >= dist) leftover -= dist;
533 maxvalue = 0xffffffffu - leftover;
539 random = g_rand_int (rand);
540 while (random > maxvalue);
546 random = 0; /* Quiet GCC */
547 g_assert_not_reached ();
550 return begin + random;
557 * Returns the next random #gdouble from @rand_ equally distributed over
560 * Return value: A random number.
563 g_rand_double (GRand* rand)
565 /* We set all 52 bits after the point for this, not only the first
566 32. Thats why we need two calls to g_rand_int */
567 gdouble retval = g_rand_int (rand) * G_RAND_DOUBLE_TRANSFORM;
568 retval = (retval + g_rand_int (rand)) * G_RAND_DOUBLE_TRANSFORM;
570 /* The following might happen due to very bad rounding luck, but
571 * actually this should be more than rare, we just try again then */
573 return g_rand_double (rand);
579 * g_rand_double_range:
581 * @begin: lower closed bound of the interval.
582 * @end: upper open bound of the interval.
584 * Returns the next random #gdouble from @rand_ equally distributed over
585 * the range [@begin..@end).
587 * Return value: A random number.
590 g_rand_double_range (GRand* rand, gdouble begin, gdouble end)
594 r = g_rand_double (rand);
596 return r * end - (r - 1) * begin;
602 * Returns a random #gboolean. This corresponds to a unbiased coin toss.
604 * Returns: a random #gboolean.
609 * Return a random #guint32 equally distributed over the range
612 * Return value: A random number.
618 G_LOCK (global_random);
620 global_random = g_rand_new ();
622 result = g_rand_int (global_random);
623 G_UNLOCK (global_random);
628 * g_random_int_range:
629 * @begin: lower closed bound of the interval.
630 * @end: upper open bound of the interval.
632 * Returns a random #gint32 equally distributed over the range
635 * Return value: A random number.
638 g_random_int_range (gint32 begin, gint32 end)
641 G_LOCK (global_random);
643 global_random = g_rand_new ();
645 result = g_rand_int_range (global_random, begin, end);
646 G_UNLOCK (global_random);
653 * Returns a random #gdouble equally distributed over the range [0..1).
655 * Return value: A random number.
658 g_random_double (void)
661 G_LOCK (global_random);
663 global_random = g_rand_new ();
665 result = g_rand_double (global_random);
666 G_UNLOCK (global_random);
671 * g_random_double_range:
672 * @begin: lower closed bound of the interval.
673 * @end: upper open bound of the interval.
675 * Returns a random #gdouble equally distributed over the range [@begin..@end).
677 * Return value: A random number.
680 g_random_double_range (gdouble begin, gdouble end)
683 G_LOCK (global_random);
685 global_random = g_rand_new ();
687 result = g_rand_double_range (global_random, begin, end);
688 G_UNLOCK (global_random);
694 * @seed: a value to reinitialize the global random number generator.
696 * Sets the seed for the global random number generator, which is used
697 * by the <function>g_random_*</function> functions, to @seed.
700 g_random_set_seed (guint32 seed)
702 G_LOCK (global_random);
704 global_random = g_rand_new_with_seed (seed);
706 g_rand_set_seed (global_random, seed);
707 G_UNLOCK (global_random);