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"
57 #include "gthreadprivate.h"
60 #include <process.h> /* For getpid() */
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). It uses the Mersenne Twister
70 * PRNG, which was originally developed by Makoto Matsumoto and Takuji
71 * Nishimura. Further information can be found at
72 * <ulink url="http://www.math.sci.hiroshima-u.ac.jp/~m-mat/MT/emt.html">
73 * http://www.math.sci.hiroshima-u.ac.jp/~m-mat/MT/emt.html</ulink>.
75 * If you just need a random number, you simply call the
76 * <function>g_random_*</function> functions, which will create a
77 * globally used #GRand and use the according
78 * <function>g_rand_*</function> functions internally. Whenever you
79 * need a stream of reproducible random numbers, you better create a
80 * #GRand yourself and use the <function>g_rand_*</function> functions
81 * directly, which will also be slightly faster. Initializing a #GRand
82 * with a certain seed will produce exactly the same series of random
83 * numbers on all platforms. This can thus be used as a seed for e.g.
86 * The <function>g_rand*_range</function> functions will return high
87 * quality equally distributed random numbers, whereas for example the
88 * <literal>(g_random_int()%max)</literal> approach often
89 * doesn't yield equally distributed numbers.
91 * GLib changed the seeding algorithm for the pseudo-random number
92 * generator Mersenne Twister, as used by
93 * <structname>GRand</structname> and <structname>GRandom</structname>.
94 * This was necessary, because some seeds would yield very bad
95 * pseudo-random streams. Also the pseudo-random integers generated by
96 * <function>g_rand*_int_range()</function> will have a slightly better
97 * equal distribution with the new version of GLib.
99 * The original seeding and generation algorithms, as found in GLib
100 * 2.0.x, can be used instead of the new ones by setting the
101 * environment variable <envar>G_RANDOM_VERSION</envar> to the value of
102 * '2.0'. Use the GLib-2.0 algorithms only if you have sequences of
103 * numbers generated with Glib-2.0 that you need to reproduce exactly.
109 * The #GRand struct is an opaque data structure. It should only be
110 * accessed through the <function>g_rand_*</function> functions.
113 G_LOCK_DEFINE_STATIC (global_random);
114 static GRand* global_random = NULL;
116 /* Period parameters */
119 #define MATRIX_A 0x9908b0df /* constant vector a */
120 #define UPPER_MASK 0x80000000 /* most significant w-r bits */
121 #define LOWER_MASK 0x7fffffff /* least significant r bits */
123 /* Tempering parameters */
124 #define TEMPERING_MASK_B 0x9d2c5680
125 #define TEMPERING_MASK_C 0xefc60000
126 #define TEMPERING_SHIFT_U(y) (y >> 11)
127 #define TEMPERING_SHIFT_S(y) (y << 7)
128 #define TEMPERING_SHIFT_T(y) (y << 15)
129 #define TEMPERING_SHIFT_L(y) (y >> 18)
132 get_random_version (void)
134 static gsize initialized = FALSE;
135 static guint random_version;
137 if (g_once_init_enter (&initialized))
139 const gchar *version_string = g_getenv ("G_RANDOM_VERSION");
140 if (!version_string || version_string[0] == '\000' ||
141 strcmp (version_string, "2.2") == 0)
143 else if (strcmp (version_string, "2.0") == 0)
147 g_warning ("Unknown G_RANDOM_VERSION \"%s\". Using version 2.2.",
151 g_once_init_leave (&initialized, TRUE);
154 return random_version;
159 guint32 mt[N]; /* the array for the state vector */
164 * g_rand_new_with_seed:
165 * @seed: a value to initialize the random number generator.
167 * Creates a new random number generator initialized with @seed.
169 * Return value: the new #GRand.
172 g_rand_new_with_seed (guint32 seed)
174 GRand *rand = g_new0 (GRand, 1);
175 g_rand_set_seed (rand, seed);
180 * g_rand_new_with_seed_array:
181 * @seed: an array of seeds to initialize the random number generator.
182 * @seed_length: an array of seeds to initialize the random number generator.
184 * Creates a new random number generator initialized with @seed.
186 * Return value: the new #GRand.
191 g_rand_new_with_seed_array (const guint32 *seed, guint seed_length)
193 GRand *rand = g_new0 (GRand, 1);
194 g_rand_set_seed_array (rand, seed, seed_length);
201 * Creates a new random number generator initialized with a seed taken
202 * either from <filename>/dev/urandom</filename> (if existing) or from
203 * the current time (as a fallback).
205 * Return value: the new #GRand.
213 static gboolean dev_urandom_exists = TRUE;
215 if (dev_urandom_exists)
222 dev_urandom = fopen("/dev/urandom", "rb");
224 while G_UNLIKELY (errno == EINTR);
230 setvbuf (dev_urandom, NULL, _IONBF, 0);
234 r = fread (seed, sizeof (seed), 1, dev_urandom);
236 while G_UNLIKELY (errno == EINTR);
239 dev_urandom_exists = FALSE;
241 fclose (dev_urandom);
244 dev_urandom_exists = FALSE;
247 static gboolean dev_urandom_exists = FALSE;
250 if (!dev_urandom_exists)
252 g_get_current_time (&now);
253 seed[0] = now.tv_sec;
254 seed[1] = now.tv_usec;
257 seed[3] = getppid ();
263 return g_rand_new_with_seed_array (seed, 4);
270 * Frees the memory allocated for the #GRand.
273 g_rand_free (GRand* rand)
275 g_return_if_fail (rand != NULL);
284 * Copies a #GRand into a new one with the same exact state as before.
285 * This way you can take a snapshot of the random number generator for
288 * Return value: the new #GRand.
293 g_rand_copy (GRand* rand)
297 g_return_val_if_fail (rand != NULL, NULL);
299 new_rand = g_new0 (GRand, 1);
300 memcpy (new_rand, rand, sizeof (GRand));
308 * @seed: a value to reinitialize the random number generator.
310 * Sets the seed for the random number generator #GRand to @seed.
313 g_rand_set_seed (GRand* rand, guint32 seed)
315 g_return_if_fail (rand != NULL);
317 switch (get_random_version ())
320 /* setting initial seeds to mt[N] using */
321 /* the generator Line 25 of Table 1 in */
322 /* [KNUTH 1981, The Art of Computer Programming */
323 /* Vol. 2 (2nd Ed.), pp102] */
325 if (seed == 0) /* This would make the PRNG procude only zeros */
326 seed = 0x6b842128; /* Just set it to another number */
329 for (rand->mti=1; rand->mti<N; rand->mti++)
330 rand->mt[rand->mti] = (69069 * rand->mt[rand->mti-1]);
334 /* See Knuth TAOCP Vol2. 3rd Ed. P.106 for multiplier. */
335 /* In the previous version (see above), MSBs of the */
336 /* seed affect only MSBs of the array mt[]. */
339 for (rand->mti=1; rand->mti<N; rand->mti++)
340 rand->mt[rand->mti] = 1812433253UL *
341 (rand->mt[rand->mti-1] ^ (rand->mt[rand->mti-1] >> 30)) + rand->mti;
344 g_assert_not_reached ();
349 * g_rand_set_seed_array:
351 * @seed: array to initialize with
352 * @seed_length: length of array
354 * Initializes the random number generator by an array of
355 * longs. Array can be of arbitrary size, though only the
356 * first 624 values are taken. This function is useful
357 * if you have many low entropy seeds, or if you require more then
358 * 32bits of actual entropy for your application.
363 g_rand_set_seed_array (GRand* rand, const guint32 *seed, guint seed_length)
367 g_return_if_fail (rand != NULL);
368 g_return_if_fail (seed_length >= 1);
370 g_rand_set_seed (rand, 19650218UL);
373 k = (N>seed_length ? N : seed_length);
376 rand->mt[i] = (rand->mt[i] ^
377 ((rand->mt[i-1] ^ (rand->mt[i-1] >> 30)) * 1664525UL))
378 + seed[j] + j; /* non linear */
379 rand->mt[i] &= 0xffffffffUL; /* for WORDSIZE > 32 machines */
383 rand->mt[0] = rand->mt[N-1];
391 rand->mt[i] = (rand->mt[i] ^
392 ((rand->mt[i-1] ^ (rand->mt[i-1] >> 30)) * 1566083941UL))
393 - i; /* non linear */
394 rand->mt[i] &= 0xffffffffUL; /* for WORDSIZE > 32 machines */
398 rand->mt[0] = rand->mt[N-1];
403 rand->mt[0] = 0x80000000UL; /* MSB is 1; assuring non-zero initial array */
409 * @Returns: a random #gboolean.
411 * Returns a random #gboolean from @rand_. This corresponds to a
412 * unbiased coin toss.
418 * Returns the next random #guint32 from @rand_ equally distributed over
419 * the range [0..2^32-1].
421 * Return value: A random number.
424 g_rand_int (GRand* rand)
427 static const guint32 mag01[2]={0x0, MATRIX_A};
428 /* mag01[x] = x * MATRIX_A for x=0,1 */
430 g_return_val_if_fail (rand != NULL, 0);
432 if (rand->mti >= N) { /* generate N words at one time */
435 for (kk=0;kk<N-M;kk++) {
436 y = (rand->mt[kk]&UPPER_MASK)|(rand->mt[kk+1]&LOWER_MASK);
437 rand->mt[kk] = rand->mt[kk+M] ^ (y >> 1) ^ mag01[y & 0x1];
440 y = (rand->mt[kk]&UPPER_MASK)|(rand->mt[kk+1]&LOWER_MASK);
441 rand->mt[kk] = rand->mt[kk+(M-N)] ^ (y >> 1) ^ mag01[y & 0x1];
443 y = (rand->mt[N-1]&UPPER_MASK)|(rand->mt[0]&LOWER_MASK);
444 rand->mt[N-1] = rand->mt[M-1] ^ (y >> 1) ^ mag01[y & 0x1];
449 y = rand->mt[rand->mti++];
450 y ^= TEMPERING_SHIFT_U(y);
451 y ^= TEMPERING_SHIFT_S(y) & TEMPERING_MASK_B;
452 y ^= TEMPERING_SHIFT_T(y) & TEMPERING_MASK_C;
453 y ^= TEMPERING_SHIFT_L(y);
458 /* transform [0..2^32] -> [0..1] */
459 #define G_RAND_DOUBLE_TRANSFORM 2.3283064365386962890625e-10
464 * @begin: lower closed bound of the interval.
465 * @end: upper open bound of the interval.
467 * Returns the next random #gint32 from @rand_ equally distributed over
468 * the range [@begin..@end-1].
470 * Return value: A random number.
473 g_rand_int_range (GRand* rand, gint32 begin, gint32 end)
475 guint32 dist = end - begin;
478 g_return_val_if_fail (rand != NULL, begin);
479 g_return_val_if_fail (end > begin, begin);
481 switch (get_random_version ())
484 if (dist <= 0x10000L) /* 2^16 */
486 /* This method, which only calls g_rand_int once is only good
487 * for (end - begin) <= 2^16, because we only have 32 bits set
488 * from the one call to g_rand_int (). */
490 /* we are using (trans + trans * trans), because g_rand_int only
491 * covers [0..2^32-1] and thus g_rand_int * trans only covers
492 * [0..1-2^-32], but the biggest double < 1 is 1-2^-52.
495 gdouble double_rand = g_rand_int (rand) *
496 (G_RAND_DOUBLE_TRANSFORM +
497 G_RAND_DOUBLE_TRANSFORM * G_RAND_DOUBLE_TRANSFORM);
499 random = (gint32) (double_rand * dist);
503 /* Now we use g_rand_double_range (), which will set 52 bits for
504 us, so that it is safe to round and still get a decent
506 random = (gint32) g_rand_double_range (rand, 0, dist);
514 /* maxvalue is set to the predecessor of the greatest
515 * multiple of dist less or equal 2^32. */
517 if (dist <= 0x80000000u) /* 2^31 */
519 /* maxvalue = 2^32 - 1 - (2^32 % dist) */
520 guint32 leftover = (0x80000000u % dist) * 2;
521 if (leftover >= dist) leftover -= dist;
522 maxvalue = 0xffffffffu - leftover;
528 random = g_rand_int (rand);
529 while (random > maxvalue);
535 random = 0; /* Quiet GCC */
536 g_assert_not_reached ();
539 return begin + random;
546 * Returns the next random #gdouble from @rand_ equally distributed over
549 * Return value: A random number.
552 g_rand_double (GRand* rand)
554 /* We set all 52 bits after the point for this, not only the first
555 32. Thats why we need two calls to g_rand_int */
556 gdouble retval = g_rand_int (rand) * G_RAND_DOUBLE_TRANSFORM;
557 retval = (retval + g_rand_int (rand)) * G_RAND_DOUBLE_TRANSFORM;
559 /* The following might happen due to very bad rounding luck, but
560 * actually this should be more than rare, we just try again then */
562 return g_rand_double (rand);
568 * g_rand_double_range:
570 * @begin: lower closed bound of the interval.
571 * @end: upper open bound of the interval.
573 * Returns the next random #gdouble from @rand_ equally distributed over
574 * the range [@begin..@end).
576 * Return value: A random number.
579 g_rand_double_range (GRand* rand, gdouble begin, gdouble end)
583 r = g_rand_double (rand);
585 return r * end - (r - 1) * begin;
590 * @Returns: a random #gboolean.
592 * Returns a random #gboolean. This corresponds to a unbiased coin toss.
597 * Return a random #guint32 equally distributed over the range
600 * Return value: A random number.
606 G_LOCK (global_random);
608 global_random = g_rand_new ();
610 result = g_rand_int (global_random);
611 G_UNLOCK (global_random);
616 * g_random_int_range:
617 * @begin: lower closed bound of the interval.
618 * @end: upper open bound of the interval.
620 * Returns a random #gint32 equally distributed over the range
623 * Return value: A random number.
626 g_random_int_range (gint32 begin, gint32 end)
629 G_LOCK (global_random);
631 global_random = g_rand_new ();
633 result = g_rand_int_range (global_random, begin, end);
634 G_UNLOCK (global_random);
641 * Returns a random #gdouble equally distributed over the range [0..1).
643 * Return value: A random number.
646 g_random_double (void)
649 G_LOCK (global_random);
651 global_random = g_rand_new ();
653 result = g_rand_double (global_random);
654 G_UNLOCK (global_random);
659 * g_random_double_range:
660 * @begin: lower closed bound of the interval.
661 * @end: upper open bound of the interval.
663 * Returns a random #gdouble equally distributed over the range [@begin..@end).
665 * Return value: A random number.
668 g_random_double_range (gdouble begin, gdouble end)
671 G_LOCK (global_random);
673 global_random = g_rand_new ();
675 result = g_rand_double_range (global_random, begin, end);
676 G_UNLOCK (global_random);
682 * @seed: a value to reinitialize the global random number generator.
684 * Sets the seed for the global random number generator, which is used
685 * by the <function>g_random_*</function> functions, to @seed.
688 g_random_set_seed (guint32 seed)
690 G_LOCK (global_random);
692 global_random = g_rand_new_with_seed (seed);
694 g_rand_set_seed (global_random, seed);
695 G_UNLOCK (global_random);