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>
52 #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 #GRand and #GRandom.
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);
126 /* Period parameters */
129 #define MATRIX_A 0x9908b0df /* constant vector a */
130 #define UPPER_MASK 0x80000000 /* most significant w-r bits */
131 #define LOWER_MASK 0x7fffffff /* least significant r bits */
133 /* Tempering parameters */
134 #define TEMPERING_MASK_B 0x9d2c5680
135 #define TEMPERING_MASK_C 0xefc60000
136 #define TEMPERING_SHIFT_U(y) (y >> 11)
137 #define TEMPERING_SHIFT_S(y) (y << 7)
138 #define TEMPERING_SHIFT_T(y) (y << 15)
139 #define TEMPERING_SHIFT_L(y) (y >> 18)
142 get_random_version (void)
144 static gsize initialized = FALSE;
145 static guint random_version;
147 if (g_once_init_enter (&initialized))
149 const gchar *version_string = g_getenv ("G_RANDOM_VERSION");
150 if (!version_string || version_string[0] == '\000' ||
151 strcmp (version_string, "2.2") == 0)
153 else if (strcmp (version_string, "2.0") == 0)
157 g_warning ("Unknown G_RANDOM_VERSION \"%s\". Using version 2.2.",
161 g_once_init_leave (&initialized, TRUE);
164 return random_version;
169 guint32 mt[N]; /* the array for the state vector */
174 * g_rand_new_with_seed:
175 * @seed: a value to initialize the random number generator.
177 * Creates a new random number generator initialized with @seed.
179 * Return value: the new #GRand.
182 g_rand_new_with_seed (guint32 seed)
184 GRand *rand = g_new0 (GRand, 1);
185 g_rand_set_seed (rand, seed);
190 * g_rand_new_with_seed_array:
191 * @seed: an array of seeds to initialize the random number generator.
192 * @seed_length: an array of seeds to initialize the random number generator.
194 * Creates a new random number generator initialized with @seed.
196 * Return value: the new #GRand.
201 g_rand_new_with_seed_array (const guint32 *seed, guint seed_length)
203 GRand *rand = g_new0 (GRand, 1);
204 g_rand_set_seed_array (rand, seed, seed_length);
211 * Creates a new random number generator initialized with a seed taken
212 * either from <filename>/dev/urandom</filename> (if existing) or from
213 * the current time (as a fallback). On Windows, the seed is taken from
216 * Return value: the new #GRand.
223 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 if (!dev_urandom_exists)
259 g_get_current_time (&now);
260 seed[0] = now.tv_sec;
261 seed[1] = now.tv_usec;
263 seed[3] = getppid ();
265 #else /* G_OS_WIN32 */
268 for (i = 0; i < G_N_ELEMENTS (seed); i++)
272 return g_rand_new_with_seed_array (seed, 4);
279 * Frees the memory allocated for the #GRand.
282 g_rand_free (GRand* rand)
284 g_return_if_fail (rand != NULL);
293 * Copies a #GRand into a new one with the same exact state as before.
294 * This way you can take a snapshot of the random number generator for
297 * Return value: the new #GRand.
302 g_rand_copy (GRand* rand)
306 g_return_val_if_fail (rand != NULL, NULL);
308 new_rand = g_new0 (GRand, 1);
309 memcpy (new_rand, rand, sizeof (GRand));
317 * @seed: a value to reinitialize the random number generator.
319 * Sets the seed for the random number generator #GRand to @seed.
322 g_rand_set_seed (GRand* rand, guint32 seed)
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
364 * longs. Array can be of arbitrary size, though only the
365 * first 624 values are taken. This function is useful
366 * if you have many low entropy seeds, or if you require more then
367 * 32bits of actual entropy for your application.
372 g_rand_set_seed_array (GRand* rand, const guint32 *seed, guint seed_length)
376 g_return_if_fail (rand != NULL);
377 g_return_if_fail (seed_length >= 1);
379 g_rand_set_seed (rand, 19650218UL);
382 k = (N>seed_length ? N : seed_length);
385 rand->mt[i] = (rand->mt[i] ^
386 ((rand->mt[i-1] ^ (rand->mt[i-1] >> 30)) * 1664525UL))
387 + seed[j] + j; /* non linear */
388 rand->mt[i] &= 0xffffffffUL; /* for WORDSIZE > 32 machines */
392 rand->mt[0] = rand->mt[N-1];
400 rand->mt[i] = (rand->mt[i] ^
401 ((rand->mt[i-1] ^ (rand->mt[i-1] >> 30)) * 1566083941UL))
402 - i; /* non linear */
403 rand->mt[i] &= 0xffffffffUL; /* for WORDSIZE > 32 machines */
407 rand->mt[0] = rand->mt[N-1];
412 rand->mt[0] = 0x80000000UL; /* MSB is 1; assuring non-zero initial array */
419 * Returns a random #gboolean from @rand_. This corresponds to a
420 * unbiased coin toss.
422 * Returns: a random #gboolean.
428 * Returns the next random #guint32 from @rand_ equally distributed over
429 * the range [0..2^32-1].
431 * Return value: A random number.
434 g_rand_int (GRand* rand)
437 static const guint32 mag01[2]={0x0, MATRIX_A};
438 /* mag01[x] = x * MATRIX_A for x=0,1 */
440 g_return_val_if_fail (rand != NULL, 0);
442 if (rand->mti >= N) { /* generate N words at one time */
445 for (kk=0;kk<N-M;kk++) {
446 y = (rand->mt[kk]&UPPER_MASK)|(rand->mt[kk+1]&LOWER_MASK);
447 rand->mt[kk] = rand->mt[kk+M] ^ (y >> 1) ^ mag01[y & 0x1];
450 y = (rand->mt[kk]&UPPER_MASK)|(rand->mt[kk+1]&LOWER_MASK);
451 rand->mt[kk] = rand->mt[kk+(M-N)] ^ (y >> 1) ^ mag01[y & 0x1];
453 y = (rand->mt[N-1]&UPPER_MASK)|(rand->mt[0]&LOWER_MASK);
454 rand->mt[N-1] = rand->mt[M-1] ^ (y >> 1) ^ mag01[y & 0x1];
459 y = rand->mt[rand->mti++];
460 y ^= TEMPERING_SHIFT_U(y);
461 y ^= TEMPERING_SHIFT_S(y) & TEMPERING_MASK_B;
462 y ^= TEMPERING_SHIFT_T(y) & TEMPERING_MASK_C;
463 y ^= TEMPERING_SHIFT_L(y);
468 /* transform [0..2^32] -> [0..1] */
469 #define G_RAND_DOUBLE_TRANSFORM 2.3283064365386962890625e-10
474 * @begin: lower closed bound of the interval.
475 * @end: upper open bound of the interval.
477 * Returns the next random #gint32 from @rand_ equally distributed over
478 * the range [@begin..@end-1].
480 * Return value: A random number.
483 g_rand_int_range (GRand* rand, gint32 begin, gint32 end)
485 guint32 dist = end - begin;
488 g_return_val_if_fail (rand != NULL, begin);
489 g_return_val_if_fail (end > begin, begin);
491 switch (get_random_version ())
494 if (dist <= 0x10000L) /* 2^16 */
496 /* This method, which only calls g_rand_int once is only good
497 * for (end - begin) <= 2^16, because we only have 32 bits set
498 * from the one call to g_rand_int (). */
500 /* we are using (trans + trans * trans), because g_rand_int only
501 * covers [0..2^32-1] and thus g_rand_int * trans only covers
502 * [0..1-2^-32], but the biggest double < 1 is 1-2^-52.
505 gdouble double_rand = g_rand_int (rand) *
506 (G_RAND_DOUBLE_TRANSFORM +
507 G_RAND_DOUBLE_TRANSFORM * G_RAND_DOUBLE_TRANSFORM);
509 random = (gint32) (double_rand * dist);
513 /* Now we use g_rand_double_range (), which will set 52 bits for
514 us, so that it is safe to round and still get a decent
516 random = (gint32) g_rand_double_range (rand, 0, dist);
524 /* maxvalue is set to the predecessor of the greatest
525 * multiple of dist less or equal 2^32. */
527 if (dist <= 0x80000000u) /* 2^31 */
529 /* maxvalue = 2^32 - 1 - (2^32 % dist) */
530 guint32 leftover = (0x80000000u % dist) * 2;
531 if (leftover >= dist) leftover -= dist;
532 maxvalue = 0xffffffffu - leftover;
538 random = g_rand_int (rand);
539 while (random > maxvalue);
545 random = 0; /* Quiet GCC */
546 g_assert_not_reached ();
549 return begin + random;
556 * Returns the next random #gdouble from @rand_ equally distributed over
559 * Return value: A random number.
562 g_rand_double (GRand* rand)
564 /* We set all 52 bits after the point for this, not only the first
565 32. Thats why we need two calls to g_rand_int */
566 gdouble retval = g_rand_int (rand) * G_RAND_DOUBLE_TRANSFORM;
567 retval = (retval + g_rand_int (rand)) * G_RAND_DOUBLE_TRANSFORM;
569 /* The following might happen due to very bad rounding luck, but
570 * actually this should be more than rare, we just try again then */
572 return g_rand_double (rand);
578 * g_rand_double_range:
580 * @begin: lower closed bound of the interval.
581 * @end: upper open bound of the interval.
583 * Returns the next random #gdouble from @rand_ equally distributed over
584 * the range [@begin..@end).
586 * Return value: A random number.
589 g_rand_double_range (GRand* rand, gdouble begin, gdouble end)
593 r = g_rand_double (rand);
595 return r * end - (r - 1) * begin;
599 get_global_random (void)
601 static GRand *global_random;
603 /* called while locked */
605 global_random = g_rand_new ();
607 return global_random;
613 * Returns a random #gboolean. This corresponds to a unbiased coin toss.
615 * Returns: a random #gboolean.
620 * Return a random #guint32 equally distributed over the range
623 * Return value: A random number.
629 G_LOCK (global_random);
630 result = g_rand_int (get_global_random ());
631 G_UNLOCK (global_random);
636 * g_random_int_range:
637 * @begin: lower closed bound of the interval.
638 * @end: upper open bound of the interval.
640 * Returns a random #gint32 equally distributed over the range
643 * Return value: A random number.
646 g_random_int_range (gint32 begin, gint32 end)
649 G_LOCK (global_random);
650 result = g_rand_int_range (get_global_random (), begin, end);
651 G_UNLOCK (global_random);
658 * Returns a random #gdouble equally distributed over the range [0..1).
660 * Return value: A random number.
663 g_random_double (void)
666 G_LOCK (global_random);
667 result = g_rand_double (get_global_random ());
668 G_UNLOCK (global_random);
673 * g_random_double_range:
674 * @begin: lower closed bound of the interval.
675 * @end: upper open bound of the interval.
677 * Returns a random #gdouble equally distributed over the range [@begin..@end).
679 * Return value: A random number.
682 g_random_double_range (gdouble begin, gdouble end)
685 G_LOCK (global_random);
686 result = g_rand_double_range (get_global_random (), begin, end);
687 G_UNLOCK (global_random);
693 * @seed: a value to reinitialize the global random number generator.
695 * Sets the seed for the global random number generator, which is used
696 * by the <function>g_random_*</function> functions, to @seed.
699 g_random_set_seed (guint32 seed)
701 G_LOCK (global_random);
702 g_rand_set_seed (get_global_random (), seed);
703 G_UNLOCK (global_random);