glib/grand.c

   1 /* GLIB - Library of useful routines for C programming
   2  * Copyright (C) 1995-1997  Peter Mattis, Spencer Kimball and Josh MacDonald
   3  *
   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.
   8  *
   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.
  13  *
  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.
  18  */
  19
  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.
  26  */
  27
  28 /*
  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/.
  33  */
  34
  35 /*
  36  * MT safe
  37  */
  38
  39 #include "config.h"
  40
  41 #include <math.h>
  42 #include <errno.h>
  43 #include <stdio.h>
  44 #include <string.h>
  45 #include <sys/types.h>
  46 #ifdef HAVE_UNISTD_H
  47 #include <unistd.h>
  48 #endif
  49
  50 #include "glib.h"
  51 #include "gthreadprivate.h"
  52 #include "galias.h"
  53
  54 #ifdef G_OS_WIN32
  55 #include <process.h>            /* For getpid() */
  56 #endif
  57
  58 G_LOCK_DEFINE_STATIC (global_random);
  59 static GRand* global_random = NULL;
  60
  61 /* Period parameters */
  62 #define N 624
  63 #define M 397
  64 #define MATRIX_A 0x9908b0df   /* constant vector a */
  65 #define UPPER_MASK 0x80000000 /* most significant w-r bits */
  66 #define LOWER_MASK 0x7fffffff /* least significant r bits */
  67
  68 /* Tempering parameters */
  69 #define TEMPERING_MASK_B 0x9d2c5680
  70 #define TEMPERING_MASK_C 0xefc60000
  71 #define TEMPERING_SHIFT_U(y)  (y >> 11)
  72 #define TEMPERING_SHIFT_S(y)  (y << 7)
  73 #define TEMPERING_SHIFT_T(y)  (y << 15)
  74 #define TEMPERING_SHIFT_L(y)  (y >> 18)
  75
  76 static guint
  77 get_random_version (void)
  78 {
  79   static gboolean initialized = FALSE;
  80   static guint random_version;
  81
  82   if (!initialized)
  83     {
  84       const gchar *version_string = g_getenv ("G_RANDOM_VERSION");
  85       if (!version_string || version_string[0] == '\000' ||
  86           strcmp (version_string, "2.2") == 0)
  87         random_version = 22;
  88       else if (strcmp (version_string, "2.0") == 0)
  89         random_version = 20;
  90       else
  91         {
  92           g_warning ("Unknown G_RANDOM_VERSION \"%s\". Using version 2.2.",
  93                      version_string);
  94           random_version = 22;
  95         }
  96       initialized = TRUE;
  97     }
  98
  99   return random_version;
 100 }
 101
 102 /* This is called from g_thread_init(). It's used to
 103  * initialize some static data in a threadsafe way.
 104  */
 105 void
 106 _g_rand_thread_init (void)
 107 {
 108   (void)get_random_version ();
 109 }
 110
 111 struct _GRand
 112 {
 113   guint32 mt[N]; /* the array for the state vector  */
 114   guint mti;
 115 };
 116
 117 /**
 118  * g_rand_new_with_seed:
 119  * @seed: a value to initialize the random number generator.
 120  *
 121  * Creates a new random number generator initialized with @seed.
 122  *
 123  * Return value: the new #GRand.
 124  **/
 125 GRand*
 126 g_rand_new_with_seed (guint32 seed)
 127 {
 128   GRand *rand = g_new0 (GRand, 1);
 129   g_rand_set_seed (rand, seed);
 130   return rand;
 131 }
 132
 133 /**
 134  * g_rand_new_with_seed_array:
 135  * @seed: an array of seeds to initialize the random number generator.
 136  * @seed_length: an array of seeds to initialize the random number generator.
 137  *
 138  * Creates a new random number generator initialized with @seed.
 139  *
 140  * Return value: the new #GRand.
 141  *
 142  * Since: 2.4
 143  **/
 144 GRand*
 145 g_rand_new_with_seed_array (const guint32 *seed, guint seed_length)
 146 {
 147   GRand *rand = g_new0 (GRand, 1);
 148   g_rand_set_seed_array (rand, seed, seed_length);
 149   return rand;
 150 }
 151
 152 /**
 153  * g_rand_new:
 154  *
 155  * Creates a new random number generator initialized with a seed taken
 156  * either from <filename>/dev/urandom</filename> (if existing) or from
 157  * the current time (as a fallback).
 158  *
 159  * Return value: the new #GRand.
 160  **/
 161 GRand*
 162 g_rand_new (void)
 163 {
 164   guint32 seed[4];
 165   GTimeVal now;
 166 #ifdef G_OS_UNIX
 167   static gboolean dev_urandom_exists = TRUE;
 168
 169   if (dev_urandom_exists)
 170     {
 171       FILE* dev_urandom;
 172
 173       do
 174         {
 175           errno = 0;
 176           dev_urandom = fopen("/dev/urandom", "rb");
 177         }
 178       while G_UNLIKELY (errno == EINTR);
 179
 180       if (dev_urandom)
 181         {
 182           int r;
 183
 184           do
 185             {
 186               errno = 0;
 187               r = fread (seed, sizeof (seed), 1, dev_urandom);
 188             }
 189           while G_UNLIKELY (errno == EINTR);
 190
 191           if (r != 1)
 192             dev_urandom_exists = FALSE;
 193
 194           fclose (dev_urandom);
 195         }
 196       else
 197         dev_urandom_exists = FALSE;
 198     }
 199 #else
 200   static gboolean dev_urandom_exists = FALSE;
 201 #endif
 202
 203   if (!dev_urandom_exists)
 204     {
 205       g_get_current_time (&now);
 206       seed[0] = now.tv_sec;
 207       seed[1] = now.tv_usec;
 208       seed[2] = getpid ();
 209 #ifdef G_OS_UNIX
 210       seed[3] = getppid ();
 211 #else
 212       seed[3] = 0;
 213 #endif
 214     }
 215
 216   return g_rand_new_with_seed_array (seed, 4);
 217 }
 218
 219 /**
 220  * g_rand_free:
 221  * @rand_: a #GRand.
 222  *
 223  * Frees the memory allocated for the #GRand.
 224  **/
 225 void
 226 g_rand_free (GRand* rand)
 227 {
 228   g_return_if_fail (rand != NULL);
 229
 230   g_free (rand);
 231 }
 232
 233 /**
 234  * g_rand_copy:
 235  * @rand_: a #GRand.
 236  *
 237  * Copies a #GRand into a new one with the same exact state as before.
 238  * This way you can take a snapshot of the random number generator for
 239  * replaying later.
 240  *
 241  * Return value: the new #GRand.
 242  *
 243  * Since: 2.4
 244  **/
 245 GRand *
 246 g_rand_copy (GRand* rand)
 247 {
 248   GRand* new_rand;
 249
 250   g_return_val_if_fail (rand != NULL, NULL);
 251
 252   new_rand = g_new0 (GRand, 1);
 253   memcpy (new_rand, rand, sizeof (GRand));
 254
 255   return new_rand;
 256 }
 257
 258 /**
 259  * g_rand_set_seed:
 260  * @rand_: a #GRand.
 261  * @seed: a value to reinitialize the random number generator.
 262  *
 263  * Sets the seed for the random number generator #GRand to @seed.
 264  **/
 265 void
 266 g_rand_set_seed (GRand* rand, guint32 seed)
 267 {
 268   g_return_if_fail (rand != NULL);
 269
 270   switch (get_random_version ())
 271     {
 272     case 20:
 273       /* setting initial seeds to mt[N] using         */
 274       /* the generator Line 25 of Table 1 in          */
 275       /* [KNUTH 1981, The Art of Computer Programming */
 276       /*    Vol. 2 (2nd Ed.), pp102]                  */
 277
 278       if (seed == 0) /* This would make the PRNG procude only zeros */
 279         seed = 0x6b842128; /* Just set it to another number */
 280
 281       rand->mt[0]= seed;
 282       for (rand->mti=1; rand->mti<N; rand->mti++)
 283         rand->mt[rand->mti] = (69069 * rand->mt[rand->mti-1]);
 284
 285       break;
 286     case 22:
 287       /* See Knuth TAOCP Vol2. 3rd Ed. P.106 for multiplier. */
 288       /* In the previous version (see above), MSBs of the    */
 289       /* seed affect only MSBs of the array mt[].            */
 290
 291       rand->mt[0]= seed;
 292       for (rand->mti=1; rand->mti<N; rand->mti++)
 293         rand->mt[rand->mti] = 1812433253UL *
 294           (rand->mt[rand->mti-1] ^ (rand->mt[rand->mti-1] >> 30)) + rand->mti;
 295       break;
 296     default:
 297       g_assert_not_reached ();
 298     }
 299 }
 300
 301 /**
 302  * g_rand_set_seed_array:
 303  * @rand_: a #GRand.
 304  * @seed: array to initialize with
 305  * @seed_length: length of array
 306  *
 307  * Initializes the random number generator by an array of
 308  * longs.  Array can be of arbitrary size, though only the
 309  * first 624 values are taken.  This function is useful
 310  * if you have many low entropy seeds, or if you require more then
 311  * 32bits of actual entropy for your application.
 312  *
 313  * Since: 2.4
 314  **/
 315 void
 316 g_rand_set_seed_array (GRand* rand, const guint32 *seed, guint seed_length)
 317 {
 318   int i, j, k;
 319
 320   g_return_if_fail (rand != NULL);
 321   g_return_if_fail (seed_length >= 1);
 322
 323   g_rand_set_seed (rand, 19650218UL);
 324
 325   i=1; j=0;
 326   k = (N>seed_length ? N : seed_length);
 327   for (; k; k--)
 328     {
 329       rand->mt[i] = (rand->mt[i] ^
 330                      ((rand->mt[i-1] ^ (rand->mt[i-1] >> 30)) * 1664525UL))
 331               + seed[j] + j; /* non linear */
 332       rand->mt[i] &= 0xffffffffUL; /* for WORDSIZE > 32 machines */
 333       i++; j++;
 334       if (i>=N)
 335         {
 336           rand->mt[0] = rand->mt[N-1];
 337           i=1;
 338         }
 339       if (j>=seed_length)
 340         j=0;
 341     }
 342   for (k=N-1; k; k--)
 343     {
 344       rand->mt[i] = (rand->mt[i] ^
 345                      ((rand->mt[i-1] ^ (rand->mt[i-1] >> 30)) * 1566083941UL))
 346               - i; /* non linear */
 347       rand->mt[i] &= 0xffffffffUL; /* for WORDSIZE > 32 machines */
 348       i++;
 349       if (i>=N)
 350         {
 351           rand->mt[0] = rand->mt[N-1];
 352           i=1;
 353         }
 354     }
 355
 356   rand->mt[0] = 0x80000000UL; /* MSB is 1; assuring non-zero initial array */
 357 }
 358
 359 /**
 360  * g_rand_int:
 361  * @rand_: a #GRand.
 362  *
 363  * Returns the next random #guint32 from @rand_ equally distributed over
 364  * the range [0..2^32-1].
 365  *
 366  * Return value: A random number.
 367  **/
 368 guint32
 369 g_rand_int (GRand* rand)
 370 {
 371   guint32 y;
 372   static const guint32 mag01[2]={0x0, MATRIX_A};
 373   /* mag01[x] = x * MATRIX_A  for x=0,1 */
 374
 375   g_return_val_if_fail (rand != NULL, 0);
 376
 377   if (rand->mti >= N) { /* generate N words at one time */
 378     int kk;
 379
 380     for (kk=0;kk<N-M;kk++) {
 381       y = (rand->mt[kk]&UPPER_MASK)|(rand->mt[kk+1]&LOWER_MASK);
 382       rand->mt[kk] = rand->mt[kk+M] ^ (y >> 1) ^ mag01[y & 0x1];
 383     }
 384     for (;kk<N-1;kk++) {
 385       y = (rand->mt[kk]&UPPER_MASK)|(rand->mt[kk+1]&LOWER_MASK);
 386       rand->mt[kk] = rand->mt[kk+(M-N)] ^ (y >> 1) ^ mag01[y & 0x1];
 387     }
 388     y = (rand->mt[N-1]&UPPER_MASK)|(rand->mt[0]&LOWER_MASK);
 389     rand->mt[N-1] = rand->mt[M-1] ^ (y >> 1) ^ mag01[y & 0x1];
 390
 391     rand->mti = 0;
 392   }
 393
 394   y = rand->mt[rand->mti++];
 395   y ^= TEMPERING_SHIFT_U(y);
 396   y ^= TEMPERING_SHIFT_S(y) & TEMPERING_MASK_B;
 397   y ^= TEMPERING_SHIFT_T(y) & TEMPERING_MASK_C;
 398   y ^= TEMPERING_SHIFT_L(y);
 399
 400   return y;
 401 }
 402
 403 /* transform [0..2^32] -> [0..1] */
 404 #define G_RAND_DOUBLE_TRANSFORM 2.3283064365386962890625e-10
 405
 406 /**
 407  * g_rand_int_range:
 408  * @rand_: a #GRand.
 409  * @begin: lower closed bound of the interval.
 410  * @end: upper open bound of the interval.
 411  *
 412  * Returns the next random #gint32 from @rand_ equally distributed over
 413  * the range [@begin..@end-1].
 414  *
 415  * Return value: A random number.
 416  **/
 417 gint32
 418 g_rand_int_range (GRand* rand, gint32 begin, gint32 end)
 419 {
 420   guint32 dist = end - begin;
 421   guint32 random;
 422
 423   g_return_val_if_fail (rand != NULL, begin);
 424   g_return_val_if_fail (end > begin, begin);
 425
 426   switch (get_random_version ())
 427     {
 428     case 20:
 429       if (dist <= 0x10000L) /* 2^16 */
 430         {
 431           /* This method, which only calls g_rand_int once is only good
 432            * for (end - begin) <= 2^16, because we only have 32 bits set
 433            * from the one call to g_rand_int (). */
 434
 435           /* we are using (trans + trans * trans), because g_rand_int only
 436            * covers [0..2^32-1] and thus g_rand_int * trans only covers
 437            * [0..1-2^-32], but the biggest double < 1 is 1-2^-52.
 438            */
 439
 440           gdouble double_rand = g_rand_int (rand) *
 441             (G_RAND_DOUBLE_TRANSFORM +
 442              G_RAND_DOUBLE_TRANSFORM * G_RAND_DOUBLE_TRANSFORM);
 443
 444           random = (gint32) (double_rand * dist);
 445         }
 446       else
 447         {
 448           /* Now we use g_rand_double_range (), which will set 52 bits for
 449              us, so that it is safe to round and still get a decent
 450              distribution */
 451           random = (gint32) g_rand_double_range (rand, 0, dist);
 452         }
 453       break;
 454     case 22:
 455       if (dist == 0)
 456         random = 0;
 457       else
 458         {
 459           /* maxvalue is set to the predecessor of the greatest
 460            * multiple of dist less or equal 2^32. */
 461           guint32 maxvalue;
 462           if (dist <= 0x80000000u) /* 2^31 */
 463             {
 464               /* maxvalue = 2^32 - 1 - (2^32 % dist) */
 465               guint32 leftover = (0x80000000u % dist) * 2;
 466               if (leftover >= dist) leftover -= dist;
 467               maxvalue = 0xffffffffu - leftover;
 468             }
 469           else
 470             maxvalue = dist - 1;
 471
 472           do
 473             random = g_rand_int (rand);
 474           while (random > maxvalue);
 475
 476           random %= dist;
 477         }
 478       break;
 479     default:
 480       random = 0;               /* Quiet GCC */
 481       g_assert_not_reached ();
 482     }
 483
 484   return begin + random;
 485 }
 486
 487 /**
 488  * g_rand_double:
 489  * @rand_: a #GRand.
 490  *
 491  * Returns the next random #gdouble from @rand_ equally distributed over
 492  * the range [0..1).
 493  *
 494  * Return value: A random number.
 495  **/
 496 gdouble
 497 g_rand_double (GRand* rand)
 498 {
 499   /* We set all 52 bits after the point for this, not only the first
 500      32. Thats why we need two calls to g_rand_int */
 501   gdouble retval = g_rand_int (rand) * G_RAND_DOUBLE_TRANSFORM;
 502   retval = (retval + g_rand_int (rand)) * G_RAND_DOUBLE_TRANSFORM;
 503
 504   /* The following might happen due to very bad rounding luck, but
 505    * actually this should be more than rare, we just try again then */
 506   if (retval >= 1.0)
 507     return g_rand_double (rand);
 508
 509   return retval;
 510 }
 511
 512 /**
 513  * g_rand_double_range:
 514  * @rand_: a #GRand.
 515  * @begin: lower closed bound of the interval.
 516  * @end: upper open bound of the interval.
 517  *
 518  * Returns the next random #gdouble from @rand_ equally distributed over
 519  * the range [@begin..@end).
 520  *
 521  * Return value: A random number.
 522  **/
 523 gdouble
 524 g_rand_double_range (GRand* rand, gdouble begin, gdouble end)
 525 {
 526   return g_rand_double (rand) * (end - begin) + begin;
 527 }
 528
 529 /**
 530  * g_random_int:
 531  *
 532  * Return a random #guint32 equally distributed over the range
 533  * [0..2^32-1].
 534  *
 535  * Return value: A random number.
 536  **/
 537 guint32
 538 g_random_int (void)
 539 {
 540   guint32 result;
 541   G_LOCK (global_random);
 542   if (!global_random)
 543     global_random = g_rand_new ();
 544
 545   result = g_rand_int (global_random);
 546   G_UNLOCK (global_random);
 547   return result;
 548 }
 549
 550 /**
 551  * g_random_int_range:
 552  * @begin: lower closed bound of the interval.
 553  * @end: upper open bound of the interval.
 554  *
 555  * Returns a random #gint32 equally distributed over the range
 556  * [@begin..@end-1].
 557  *
 558  * Return value: A random number.
 559  **/
 560 gint32
 561 g_random_int_range (gint32 begin, gint32 end)
 562 {
 563   gint32 result;
 564   G_LOCK (global_random);
 565   if (!global_random)
 566     global_random = g_rand_new ();
 567
 568   result = g_rand_int_range (global_random, begin, end);
 569   G_UNLOCK (global_random);
 570   return result;
 571 }
 572
 573 /**
 574  * g_random_double:
 575  *
 576  * Returns a random #gdouble equally distributed over the range [0..1).
 577  *
 578  * Return value: A random number.
 579  **/
 580 gdouble
 581 g_random_double (void)
 582 {
 583   double result;
 584   G_LOCK (global_random);
 585   if (!global_random)
 586     global_random = g_rand_new ();
 587
 588   result = g_rand_double (global_random);
 589   G_UNLOCK (global_random);
 590   return result;
 591 }
 592
 593 /**
 594  * g_random_double_range:
 595  * @begin: lower closed bound of the interval.
 596  * @end: upper open bound of the interval.
 597  *
 598  * Returns a random #gdouble equally distributed over the range [@begin..@end).
 599  *
 600  * Return value: A random number.
 601  **/
 602 gdouble
 603 g_random_double_range (gdouble begin, gdouble end)
 604 {
 605   double result;
 606   G_LOCK (global_random);
 607   if (!global_random)
 608     global_random = g_rand_new ();
 609
 610   result = g_rand_double_range (global_random, begin, end);
 611   G_UNLOCK (global_random);
 612   return result;
 613 }
 614
 615 /**
 616  * g_random_set_seed:
 617  * @seed: a value to reinitialize the global random number generator.
 618  *
 619  * Sets the seed for the global random number generator, which is used
 620  * by the <function>g_random_*</function> functions, to @seed.
 621  **/
 622 void
 623 g_random_set_seed (guint32 seed)
 624 {
 625   G_LOCK (global_random);
 626   if (!global_random)
 627     global_random = g_rand_new_with_seed (seed);
 628   else
 629     g_rand_set_seed (global_random, seed);
 630   G_UNLOCK (global_random);
 631 }
 632
 633
 634 #define __G_RAND_C__
 635 #include "galiasdef.c"