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 * <warning><para>Do not use this API for cryptographic purposes such as key
70 * generation, nonces, salts or one-time pads.</para></warning>
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
86 * <function>g_random_*</function> functions, which will create a
87 * globally used #GRand and use the according
88 * <function>g_rand_*</function> functions internally. Whenever you
89 * need a stream of reproducible random numbers, you better create a
90 * #GRand yourself and use the <function>g_rand_*</function> functions
91 * directly, which will also be slightly faster. Initializing a #GRand
92 * with a certain seed will produce exactly the same series of random
93 * numbers on all platforms. This can thus be used as a seed for e.g.
96 * The <function>g_rand*_range</function> functions will return high
97 * quality equally distributed random numbers, whereas for example the
98 * <literal>(g_random_int()%max)</literal> approach often
99 * doesn't yield equally distributed numbers.
101 * GLib changed the seeding algorithm for the pseudo-random number
102 * generator Mersenne Twister, as used by #GRand and #GRandom.
103 * This was necessary, because some seeds would yield very bad
104 * pseudo-random streams. Also the pseudo-random integers generated by
105 * <function>g_rand*_int_range()</function> will have a slightly better
106 * equal distribution with the new version of GLib.
108 * The original seeding and generation algorithms, as found in GLib
109 * 2.0.x, can be used instead of the new ones by setting the
110 * environment variable <envar>G_RANDOM_VERSION</envar> to the value of
111 * '2.0'. Use the GLib-2.0 algorithms only if you have sequences of
112 * numbers generated with Glib-2.0 that you need to reproduce exactly.
118 * The #GRand struct is an opaque data structure. It should only be
119 * accessed through the <function>g_rand_*</function> functions.
122 G_LOCK_DEFINE_STATIC (global_random);
124 /* Period parameters */
127 #define MATRIX_A 0x9908b0df /* constant vector a */
128 #define UPPER_MASK 0x80000000 /* most significant w-r bits */
129 #define LOWER_MASK 0x7fffffff /* least significant r bits */
131 /* Tempering parameters */
132 #define TEMPERING_MASK_B 0x9d2c5680
133 #define TEMPERING_MASK_C 0xefc60000
134 #define TEMPERING_SHIFT_U(y) (y >> 11)
135 #define TEMPERING_SHIFT_S(y) (y << 7)
136 #define TEMPERING_SHIFT_T(y) (y << 15)
137 #define TEMPERING_SHIFT_L(y) (y >> 18)
140 get_random_version (void)
142 static gsize initialized = FALSE;
143 static guint random_version;
145 if (g_once_init_enter (&initialized))
147 const gchar *version_string = g_getenv ("G_RANDOM_VERSION");
148 if (!version_string || version_string[0] == '\000' ||
149 strcmp (version_string, "2.2") == 0)
151 else if (strcmp (version_string, "2.0") == 0)
155 g_warning ("Unknown G_RANDOM_VERSION \"%s\". Using version 2.2.",
159 g_once_init_leave (&initialized, TRUE);
162 return random_version;
167 guint32 mt[N]; /* the array for the state vector */
172 * g_rand_new_with_seed:
173 * @seed: a value to initialize the random number generator.
175 * Creates a new random number generator initialized with @seed.
177 * Return value: the new #GRand.
180 g_rand_new_with_seed (guint32 seed)
182 GRand *rand = g_new0 (GRand, 1);
183 g_rand_set_seed (rand, seed);
188 * g_rand_new_with_seed_array:
189 * @seed: an array of seeds to initialize the random number generator.
190 * @seed_length: an array of seeds to initialize the random number generator.
192 * Creates a new random number generator initialized with @seed.
194 * Return value: the new #GRand.
199 g_rand_new_with_seed_array (const guint32 *seed, guint seed_length)
201 GRand *rand = g_new0 (GRand, 1);
202 g_rand_set_seed_array (rand, seed, seed_length);
209 * Creates a new random number generator initialized with a seed taken
210 * either from <filename>/dev/urandom</filename> (if existing) or from
211 * the current time (as a fallback). On Windows, the seed is taken from
214 * Return value: the new #GRand.
221 static gboolean dev_urandom_exists = TRUE;
224 if (dev_urandom_exists)
230 dev_urandom = fopen("/dev/urandom", "rb");
232 while G_UNLIKELY (dev_urandom == NULL && errno == EINTR);
238 setvbuf (dev_urandom, NULL, _IONBF, 0);
242 r = fread (seed, sizeof (seed), 1, dev_urandom);
244 while G_UNLIKELY (errno == EINTR);
247 dev_urandom_exists = FALSE;
249 fclose (dev_urandom);
252 dev_urandom_exists = FALSE;
255 if (!dev_urandom_exists)
257 g_get_current_time (&now);
258 seed[0] = now.tv_sec;
259 seed[1] = now.tv_usec;
261 seed[3] = getppid ();
263 #else /* G_OS_WIN32 */
266 for (i = 0; i < G_N_ELEMENTS (seed); i++)
270 return g_rand_new_with_seed_array (seed, 4);
277 * Frees the memory allocated for the #GRand.
280 g_rand_free (GRand* rand)
282 g_return_if_fail (rand != NULL);
291 * Copies a #GRand into a new one with the same exact state as before.
292 * This way you can take a snapshot of the random number generator for
295 * Return value: the new #GRand.
300 g_rand_copy (GRand* rand)
304 g_return_val_if_fail (rand != NULL, NULL);
306 new_rand = g_new0 (GRand, 1);
307 memcpy (new_rand, rand, sizeof (GRand));
315 * @seed: a value to reinitialize the random number generator.
317 * Sets the seed for the random number generator #GRand to @seed.
320 g_rand_set_seed (GRand* rand, guint32 seed)
322 g_return_if_fail (rand != NULL);
324 switch (get_random_version ())
327 /* setting initial seeds to mt[N] using */
328 /* the generator Line 25 of Table 1 in */
329 /* [KNUTH 1981, The Art of Computer Programming */
330 /* Vol. 2 (2nd Ed.), pp102] */
332 if (seed == 0) /* This would make the PRNG produce only zeros */
333 seed = 0x6b842128; /* Just set it to another number */
336 for (rand->mti=1; rand->mti<N; rand->mti++)
337 rand->mt[rand->mti] = (69069 * rand->mt[rand->mti-1]);
341 /* See Knuth TAOCP Vol2. 3rd Ed. P.106 for multiplier. */
342 /* In the previous version (see above), MSBs of the */
343 /* seed affect only MSBs of the array mt[]. */
346 for (rand->mti=1; rand->mti<N; rand->mti++)
347 rand->mt[rand->mti] = 1812433253UL *
348 (rand->mt[rand->mti-1] ^ (rand->mt[rand->mti-1] >> 30)) + rand->mti;
351 g_assert_not_reached ();
356 * g_rand_set_seed_array:
358 * @seed: array to initialize with
359 * @seed_length: length of array
361 * Initializes the random number generator by an array of
362 * longs. Array can be of arbitrary size, though only the
363 * first 624 values are taken. This function is useful
364 * if you have many low entropy seeds, or if you require more then
365 * 32bits of actual entropy for your application.
370 g_rand_set_seed_array (GRand* rand, const guint32 *seed, guint seed_length)
374 g_return_if_fail (rand != NULL);
375 g_return_if_fail (seed_length >= 1);
377 g_rand_set_seed (rand, 19650218UL);
380 k = (N>seed_length ? N : seed_length);
383 rand->mt[i] = (rand->mt[i] ^
384 ((rand->mt[i-1] ^ (rand->mt[i-1] >> 30)) * 1664525UL))
385 + seed[j] + j; /* non linear */
386 rand->mt[i] &= 0xffffffffUL; /* for WORDSIZE > 32 machines */
390 rand->mt[0] = rand->mt[N-1];
398 rand->mt[i] = (rand->mt[i] ^
399 ((rand->mt[i-1] ^ (rand->mt[i-1] >> 30)) * 1566083941UL))
400 - i; /* non linear */
401 rand->mt[i] &= 0xffffffffUL; /* for WORDSIZE > 32 machines */
405 rand->mt[0] = rand->mt[N-1];
410 rand->mt[0] = 0x80000000UL; /* MSB is 1; assuring non-zero initial array */
417 * Returns a random #gboolean from @rand_. This corresponds to a
418 * unbiased coin toss.
420 * Returns: a random #gboolean.
426 * Returns the next random #guint32 from @rand_ equally distributed over
427 * the range [0..2^32-1].
429 * Return value: A random number.
432 g_rand_int (GRand* rand)
435 static const guint32 mag01[2]={0x0, MATRIX_A};
436 /* mag01[x] = x * MATRIX_A for x=0,1 */
438 g_return_val_if_fail (rand != NULL, 0);
440 if (rand->mti >= N) { /* generate N words at one time */
443 for (kk=0;kk<N-M;kk++) {
444 y = (rand->mt[kk]&UPPER_MASK)|(rand->mt[kk+1]&LOWER_MASK);
445 rand->mt[kk] = rand->mt[kk+M] ^ (y >> 1) ^ mag01[y & 0x1];
448 y = (rand->mt[kk]&UPPER_MASK)|(rand->mt[kk+1]&LOWER_MASK);
449 rand->mt[kk] = rand->mt[kk+(M-N)] ^ (y >> 1) ^ mag01[y & 0x1];
451 y = (rand->mt[N-1]&UPPER_MASK)|(rand->mt[0]&LOWER_MASK);
452 rand->mt[N-1] = rand->mt[M-1] ^ (y >> 1) ^ mag01[y & 0x1];
457 y = rand->mt[rand->mti++];
458 y ^= TEMPERING_SHIFT_U(y);
459 y ^= TEMPERING_SHIFT_S(y) & TEMPERING_MASK_B;
460 y ^= TEMPERING_SHIFT_T(y) & TEMPERING_MASK_C;
461 y ^= TEMPERING_SHIFT_L(y);
466 /* transform [0..2^32] -> [0..1] */
467 #define G_RAND_DOUBLE_TRANSFORM 2.3283064365386962890625e-10
472 * @begin: lower closed bound of the interval.
473 * @end: upper open bound of the interval.
475 * Returns the next random #gint32 from @rand_ equally distributed over
476 * the range [@begin..@end-1].
478 * Return value: A random number.
481 g_rand_int_range (GRand* rand, gint32 begin, gint32 end)
483 guint32 dist = end - begin;
486 g_return_val_if_fail (rand != NULL, begin);
487 g_return_val_if_fail (end > begin, begin);
489 switch (get_random_version ())
492 if (dist <= 0x10000L) /* 2^16 */
494 /* This method, which only calls g_rand_int once is only good
495 * for (end - begin) <= 2^16, because we only have 32 bits set
496 * from the one call to g_rand_int (). */
498 /* we are using (trans + trans * trans), because g_rand_int only
499 * covers [0..2^32-1] and thus g_rand_int * trans only covers
500 * [0..1-2^-32], but the biggest double < 1 is 1-2^-52.
503 gdouble double_rand = g_rand_int (rand) *
504 (G_RAND_DOUBLE_TRANSFORM +
505 G_RAND_DOUBLE_TRANSFORM * G_RAND_DOUBLE_TRANSFORM);
507 random = (gint32) (double_rand * dist);
511 /* Now we use g_rand_double_range (), which will set 52 bits for
512 us, so that it is safe to round and still get a decent
514 random = (gint32) g_rand_double_range (rand, 0, dist);
522 /* maxvalue is set to the predecessor of the greatest
523 * multiple of dist less or equal 2^32. */
525 if (dist <= 0x80000000u) /* 2^31 */
527 /* maxvalue = 2^32 - 1 - (2^32 % dist) */
528 guint32 leftover = (0x80000000u % dist) * 2;
529 if (leftover >= dist) leftover -= dist;
530 maxvalue = 0xffffffffu - leftover;
536 random = g_rand_int (rand);
537 while (random > maxvalue);
543 random = 0; /* Quiet GCC */
544 g_assert_not_reached ();
547 return begin + random;
554 * Returns the next random #gdouble from @rand_ equally distributed over
557 * Return value: A random number.
560 g_rand_double (GRand* rand)
562 /* We set all 52 bits after the point for this, not only the first
563 32. Thats why we need two calls to g_rand_int */
564 gdouble retval = g_rand_int (rand) * G_RAND_DOUBLE_TRANSFORM;
565 retval = (retval + g_rand_int (rand)) * G_RAND_DOUBLE_TRANSFORM;
567 /* The following might happen due to very bad rounding luck, but
568 * actually this should be more than rare, we just try again then */
570 return g_rand_double (rand);
576 * g_rand_double_range:
578 * @begin: lower closed bound of the interval.
579 * @end: upper open bound of the interval.
581 * Returns the next random #gdouble from @rand_ equally distributed over
582 * the range [@begin..@end).
584 * Return value: A random number.
587 g_rand_double_range (GRand* rand, gdouble begin, gdouble end)
591 r = g_rand_double (rand);
593 return r * end - (r - 1) * begin;
597 get_global_random (void)
599 static GRand *global_random;
601 /* called while locked */
603 global_random = g_rand_new ();
605 return global_random;
611 * Returns a random #gboolean. This corresponds to a unbiased coin toss.
613 * Returns: a random #gboolean.
618 * Return a random #guint32 equally distributed over the range
621 * Return value: A random number.
627 G_LOCK (global_random);
628 result = g_rand_int (get_global_random ());
629 G_UNLOCK (global_random);
634 * g_random_int_range:
635 * @begin: lower closed bound of the interval.
636 * @end: upper open bound of the interval.
638 * Returns a random #gint32 equally distributed over the range
641 * Return value: A random number.
644 g_random_int_range (gint32 begin, gint32 end)
647 G_LOCK (global_random);
648 result = g_rand_int_range (get_global_random (), begin, end);
649 G_UNLOCK (global_random);
656 * Returns a random #gdouble equally distributed over the range [0..1).
658 * Return value: A random number.
661 g_random_double (void)
664 G_LOCK (global_random);
665 result = g_rand_double (get_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);
684 result = g_rand_double_range (get_global_random (), begin, end);
685 G_UNLOCK (global_random);
691 * @seed: a value to reinitialize the global random number generator.
693 * Sets the seed for the global random number generator, which is used
694 * by the <function>g_random_*</function> functions, to @seed.
697 g_random_set_seed (guint32 seed)
699 G_LOCK (global_random);
700 g_rand_set_seed (get_global_random (), seed);
701 G_UNLOCK (global_random);