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.keio.ac.jp/~matumoto/emt.html
25 * This code was adapted to glib by Sebastian Wilhelmi <wilhelmi@ira.uka.de>.
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/.
43 G_LOCK_DEFINE_STATIC (global_random);
44 static GRand* global_random = NULL;
46 /* Period parameters */
49 #define MATRIX_A 0x9908b0df /* constant vector a */
50 #define UPPER_MASK 0x80000000 /* most significant w-r bits */
51 #define LOWER_MASK 0x7fffffff /* least significant r bits */
53 /* Tempering parameters */
54 #define TEMPERING_MASK_B 0x9d2c5680
55 #define TEMPERING_MASK_C 0xefc60000
56 #define TEMPERING_SHIFT_U(y) (y >> 11)
57 #define TEMPERING_SHIFT_S(y) (y << 7)
58 #define TEMPERING_SHIFT_T(y) (y << 15)
59 #define TEMPERING_SHIFT_L(y) (y >> 18)
62 get_random_version (void)
64 static gboolean initialized = FALSE;
65 static guint random_version;
69 const gchar *version_string = g_getenv ("G_RANDOM_VERSION");
70 if (!version_string || version_string[0] == '\000' ||
71 strcmp (version_string, "2.2") == 0)
73 else if (strcmp (version_string, "2.0") == 0)
77 g_warning ("Unknown G_RANDOM_VERSION \"%s\". Using version 2.2.",
84 return random_version;
87 /* This is called from g_thread_init(). It's used to
88 * initialize some static data in a threadsafe way.
93 (void)get_random_version ();
98 guint32 mt[N]; /* the array for the state vector */
103 * g_rand_new_with_seed:
104 * @seed: a value to initialize the random number generator.
106 * Creates a new random number generator initialized with @seed.
108 * Return value: the new #GRand.
111 g_rand_new_with_seed (guint32 seed)
113 GRand *rand = g_new0 (GRand, 1);
114 g_rand_set_seed (rand, seed);
121 * Creates a new random number generator initialized with a seed taken
122 * either from <filename>/dev/urandom</filename> (if existing) or from
123 * the current time (as a fallback).
125 * Return value: the new #GRand.
133 static gboolean dev_urandom_exists = TRUE;
135 if (dev_urandom_exists)
137 FILE* dev_urandom = fopen("/dev/urandom", "rb");
140 if (fread (&seed, sizeof (seed), 1, dev_urandom) != 1)
141 dev_urandom_exists = FALSE;
142 fclose (dev_urandom);
145 dev_urandom_exists = FALSE;
148 static gboolean dev_urandom_exists = FALSE;
151 if (!dev_urandom_exists)
153 g_get_current_time (&now);
154 seed = now.tv_sec ^ now.tv_usec;
157 return g_rand_new_with_seed (seed);
164 * Frees the memory allocated for the #GRand.
167 g_rand_free (GRand* rand)
169 g_return_if_fail (rand != NULL);
177 * @seed: a value to reinitialize the random number generator.
179 * Sets the seed for the random number generator #GRand to @seed.
182 g_rand_set_seed (GRand* rand, guint32 seed)
184 g_return_if_fail (rand != NULL);
186 switch (get_random_version ())
189 /* setting initial seeds to mt[N] using */
190 /* the generator Line 25 of Table 1 in */
191 /* [KNUTH 1981, The Art of Computer Programming */
192 /* Vol. 2 (2nd Ed.), pp102] */
194 if (seed == 0) /* This would make the PRNG procude only zeros */
195 seed = 0x6b842128; /* Just set it to another number */
198 for (rand->mti=1; rand->mti<N; rand->mti++)
199 rand->mt[rand->mti] = (69069 * rand->mt[rand->mti-1]);
203 /* See Knuth TAOCP Vol2. 3rd Ed. P.106 for multiplier. */
204 /* In the previous version (see above), MSBs of the */
205 /* seed affect only MSBs of the array mt[]. */
208 for (rand->mti=1; rand->mti<N; rand->mti++)
209 rand->mt[rand->mti] = 1812433253UL *
210 (rand->mt[rand->mti-1] ^ (rand->mt[rand->mti-1] >> 30)) + rand->mti;
213 g_assert_not_reached ();
221 * Returns the next random #guint32 from @rand_ equally distributed over
222 * the range [0..2^32-1].
224 * Return value: A random number.
227 g_rand_int (GRand* rand)
230 static const guint32 mag01[2]={0x0, MATRIX_A};
231 /* mag01[x] = x * MATRIX_A for x=0,1 */
233 g_return_val_if_fail (rand != NULL, 0);
235 if (rand->mti >= N) { /* generate N words at one time */
238 for (kk=0;kk<N-M;kk++) {
239 y = (rand->mt[kk]&UPPER_MASK)|(rand->mt[kk+1]&LOWER_MASK);
240 rand->mt[kk] = rand->mt[kk+M] ^ (y >> 1) ^ mag01[y & 0x1];
243 y = (rand->mt[kk]&UPPER_MASK)|(rand->mt[kk+1]&LOWER_MASK);
244 rand->mt[kk] = rand->mt[kk+(M-N)] ^ (y >> 1) ^ mag01[y & 0x1];
246 y = (rand->mt[N-1]&UPPER_MASK)|(rand->mt[0]&LOWER_MASK);
247 rand->mt[N-1] = rand->mt[M-1] ^ (y >> 1) ^ mag01[y & 0x1];
252 y = rand->mt[rand->mti++];
253 y ^= TEMPERING_SHIFT_U(y);
254 y ^= TEMPERING_SHIFT_S(y) & TEMPERING_MASK_B;
255 y ^= TEMPERING_SHIFT_T(y) & TEMPERING_MASK_C;
256 y ^= TEMPERING_SHIFT_L(y);
261 /* transform [0..2^32] -> [0..1] */
262 #define G_RAND_DOUBLE_TRANSFORM 2.3283064365386962890625e-10
267 * @begin: lower closed bound of the interval.
268 * @end: upper open bound of the interval.
270 * Returns the next random #gint32 from @rand_ equally distributed over
271 * the range [@begin..@end-1].
273 * Return value: A random number.
276 g_rand_int_range (GRand* rand, gint32 begin, gint32 end)
278 guint32 dist = end - begin;
281 g_return_val_if_fail (rand != NULL, begin);
282 g_return_val_if_fail (end > begin, begin);
284 /* All tricks doing modulo calculations do not have a perfect
285 * distribution -> We must use the slower way through gdouble for
286 * maximal quality. */
288 if (dist <= 0x10000L) /* 2^16 */
290 /* This method, which only calls g_rand_int once is only good
291 * for (end - begin) <= 2^16, because we only have 32 bits set
292 * from the one call to g_rand_int (). */
294 /* we are using (trans + trans * trans), because g_rand_int only
295 * covers [0..2^32-1] and thus g_rand_int * trans only covers
296 * [0..1-2^-32], but the biggest double < 1 is 1-2^-52.
299 gdouble double_rand = g_rand_int (rand) *
300 (G_RAND_DOUBLE_TRANSFORM +
301 G_RAND_DOUBLE_TRANSFORM * G_RAND_DOUBLE_TRANSFORM);
303 random = (gint32) (double_rand * dist);
307 /* Now we use g_rand_double_range (), which will set 52 bits for
308 us, so that it is safe to round and still get a decent
310 random = (gint32) g_rand_double_range (rand, 0, dist);
313 return begin + random;
320 * Returns the next random #gdouble from @rand_ equally distributed over
323 * Return value: A random number.
326 g_rand_double (GRand* rand)
328 /* We set all 52 bits after the point for this, not only the first
329 32. Thats why we need two calls to g_rand_int */
330 gdouble retval = g_rand_int (rand) * G_RAND_DOUBLE_TRANSFORM;
331 retval = (retval + g_rand_int (rand)) * G_RAND_DOUBLE_TRANSFORM;
333 /* The following might happen due to very bad rounding luck, but
334 * actually this should be more than rare, we just try again then */
336 return g_rand_double (rand);
342 * g_rand_double_range:
344 * @begin: lower closed bound of the interval.
345 * @end: upper open bound of the interval.
347 * Returns the next random #gdouble from @rand_ equally distributed over
348 * the range [@begin..@end).
350 * Return value: A random number.
353 g_rand_double_range (GRand* rand, gdouble begin, gdouble end)
355 return g_rand_double (rand) * (end - begin) + begin;
361 * Return a random #guint32 equally distributed over the range
364 * Return value: A random number.
370 G_LOCK (global_random);
372 global_random = g_rand_new ();
374 result = g_rand_int (global_random);
375 G_UNLOCK (global_random);
380 * g_random_int_range:
381 * @begin: lower closed bound of the interval.
382 * @end: upper open bound of the interval.
384 * Returns a random #gint32 equally distributed over the range
387 * Return value: A random number.
390 g_random_int_range (gint32 begin, gint32 end)
393 G_LOCK (global_random);
395 global_random = g_rand_new ();
397 result = g_rand_int_range (global_random, begin, end);
398 G_UNLOCK (global_random);
405 * Returns a random #gdouble equally distributed over the range [0..1).
407 * Return value: A random number.
410 g_random_double (void)
413 G_LOCK (global_random);
415 global_random = g_rand_new ();
417 result = g_rand_double (global_random);
418 G_UNLOCK (global_random);
423 * g_random_double_range:
424 * @begin: lower closed bound of the interval.
425 * @end: upper open bound of the interval.
427 * Returns a random #gdouble equally distributed over the range [@begin..@end).
429 * Return value: A random number.
432 g_random_double_range (gdouble begin, gdouble end)
435 G_LOCK (global_random);
437 global_random = g_rand_new ();
439 result = g_rand_double_range (global_random, begin, end);
440 G_UNLOCK (global_random);
446 * @seed: a value to reinitialize the global random number generator.
448 * Sets the seed for the global random number generator, which is used
449 * by the <function>g_random_*</function> functions, to @seed.
452 g_random_set_seed (guint32 seed)
454 G_LOCK (global_random);
456 global_random = g_rand_new_with_seed (seed);
458 g_rand_set_seed (global_random, seed);
459 G_UNLOCK (global_random);