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, see <http://www.gnu.org/licenses/>.
  16  */
  17
  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.
  24  */
  25
  26 /*
  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/.
  31  */
  32
  33 /*
  34  * MT safe
  35  */
  36
  37 #include "config.h"
  38 #define _CRT_RAND_S
  39
  40 #include <math.h>
  41 #include <errno.h>
  42 #include <stdio.h>
  43 #include <string.h>
  44 #include <sys/types.h>
  45 #include "grand.h"
  46
  47 #include "genviron.h"
  48 #include "gmain.h"
  49 #include "gmem.h"
  50 #include "gtestutils.h"
  51 #include "gthread.h"
  52
  53 #ifdef G_OS_UNIX
  54 #include <unistd.h>
  55 #endif
  56
  57 #ifdef G_OS_WIN32
  58 #include <stdlib.h>
  59 #include <process.h> /* For getpid() */
  60 #endif
  61
  62 /**
  63  * SECTION:random_numbers
  64  * @title: Random Numbers
  65  * @short_description: pseudo-random number generator
  66  *
  67  * The following functions allow you to use a portable, fast and good
  68  * pseudo-random number generator (PRNG).
  69  *
  70  * Do not use this API for cryptographic purposes such as key
  71  * generation, nonces, salts or one-time pads.
  72  *
  73  * This PRNG is suitable for non-cryptographic use such as in games
  74  * (shuffling a card deck, generating levels), generating data for
  75  * a test suite, etc. If you need random data for cryptographic
  76  * purposes, it is recommended to use platform-specific APIs such
  77  * as `/dev/random` on UNIX, or CryptGenRandom() on Windows.
  78  *
  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
  82  * [this page](http://www.math.sci.hiroshima-u.ac.jp/~m-mat/MT/emt.html).
  83  *
  84  * If you just need a random number, you simply call the g_random_*
  85  * functions, which will create a globally used #GRand and use the
  86  * according g_rand_* functions internally. Whenever you need a
  87  * stream of reproducible random numbers, you better create a
  88  * #GRand yourself and use the g_rand_* functions directly, which
  89  * will also be slightly faster. Initializing a #GRand with a
  90  * certain seed will produce exactly the same series of random
  91  * numbers on all platforms. This can thus be used as a seed for
  92  * e.g. games.
  93  *
  94  * The g_rand*_range functions will return high quality equally
  95  * distributed random numbers, whereas for example the
  96  * `(g_random_int()%max)` approach often
  97  * doesn't yield equally distributed numbers.
  98  *
  99  * GLib changed the seeding algorithm for the pseudo-random number
 100  * generator Mersenne Twister, as used by #GRand. This was necessary,
 101  * because some seeds would yield very bad pseudo-random streams.
 102  * Also the pseudo-random integers generated by g_rand*_int_range()
 103  * will have a slightly better equal distribution with the new
 104  * version of GLib.
 105  *
 106  * The original seeding and generation algorithms, as found in
 107  * GLib 2.0.x, can be used instead of the new ones by setting the
 108  * environment variable `G_RANDOM_VERSION` to the value of '2.0'.
 109  * Use the GLib-2.0 algorithms only if you have sequences of numbers
 110  * generated with Glib-2.0 that you need to reproduce exactly.
 111  */
 112
 113 /**
 114  * GRand:
 115  *
 116  * The GRand struct is an opaque data structure. It should only be
 117  * accessed through the g_rand_* functions.
 118  **/
 119
 120 G_LOCK_DEFINE_STATIC (global_random);
 121
 122 /* Period parameters */
 123 #define N 624
 124 #define M 397
 125 #define MATRIX_A 0x9908b0df   /* constant vector a */
 126 #define UPPER_MASK 0x80000000 /* most significant w-r bits */
 127 #define LOWER_MASK 0x7fffffff /* least significant r bits */
 128
 129 /* Tempering parameters */
 130 #define TEMPERING_MASK_B 0x9d2c5680
 131 #define TEMPERING_MASK_C 0xefc60000
 132 #define TEMPERING_SHIFT_U(y)  (y >> 11)
 133 #define TEMPERING_SHIFT_S(y)  (y << 7)
 134 #define TEMPERING_SHIFT_T(y)  (y << 15)
 135 #define TEMPERING_SHIFT_L(y)  (y >> 18)
 136
 137 static guint
 138 get_random_version (void)
 139 {
 140   static gsize initialized = FALSE;
 141   static guint random_version;
 142
 143   if (g_once_init_enter (&initialized))
 144     {
 145       const gchar *version_string = g_getenv ("G_RANDOM_VERSION");
 146       if (!version_string || version_string[0] == '\000' ||
 147           strcmp (version_string, "2.2") == 0)
 148         random_version = 22;
 149       else if (strcmp (version_string, "2.0") == 0)
 150         random_version = 20;
 151       else
 152         {
 153           g_warning ("Unknown G_RANDOM_VERSION \"%s\". Using version 2.2.",
 154                      version_string);
 155           random_version = 22;
 156         }
 157       g_once_init_leave (&initialized, TRUE);
 158     }
 159
 160   return random_version;
 161 }
 162
 163 struct _GRand
 164 {
 165   guint32 mt[N]; /* the array for the state vector  */
 166   guint mti;
 167 };
 168
 169 /**
 170  * g_rand_new_with_seed:
 171  * @seed: a value to initialize the random number generator
 172  *
 173  * Creates a new random number generator initialized with @seed.
 174  *
 175  * Returns: the new #GRand
 176  **/
 177 GRand*
 178 g_rand_new_with_seed (guint32 seed)
 179 {
 180   GRand *rand = g_new0 (GRand, 1);
 181   g_rand_set_seed (rand, seed);
 182   return rand;
 183 }
 184
 185 /**
 186  * g_rand_new_with_seed_array:
 187  * @seed: an array of seeds to initialize the random number generator
 188  * @seed_length: an array of seeds to initialize the random number
 189  *     generator
 190  *
 191  * Creates a new random number generator initialized with @seed.
 192  *
 193  * Returns: the new #GRand
 194  *
 195  * Since: 2.4
 196  */
 197 GRand*
 198 g_rand_new_with_seed_array (const guint32 *seed,
 199                             guint          seed_length)
 200 {
 201   GRand *rand = g_new0 (GRand, 1);
 202   g_rand_set_seed_array (rand, seed, seed_length);
 203   return rand;
 204 }
 205
 206 /**
 207  * g_rand_new:
 208  *
 209  * Creates a new random number generator initialized with a seed taken
 210  * either from `/dev/urandom` (if existing) or from the current time
 211  * (as a fallback).
 212  *
 213  * On Windows, the seed is taken from rand_s().
 214  *
 215  * Returns: the new #GRand
 216  */
 217 GRand*
 218 g_rand_new (void)
 219 {
 220   guint32 seed[4];
 221 #ifdef G_OS_UNIX
 222   static gboolean dev_urandom_exists = TRUE;
 223   GTimeVal now;
 224
 225   if (dev_urandom_exists)
 226     {
 227       FILE* dev_urandom;
 228
 229       do
 230         {
 231           dev_urandom = fopen("/dev/urandom", "rb");
 232         }
 233       while G_UNLIKELY (dev_urandom == NULL && errno == EINTR);
 234
 235       if (dev_urandom)
 236         {
 237           int r;
 238
 239           setvbuf (dev_urandom, NULL, _IONBF, 0);
 240           do
 241             {
 242               errno = 0;
 243               r = fread (seed, sizeof (seed), 1, dev_urandom);
 244             }
 245           while G_UNLIKELY (errno == EINTR);
 246
 247           if (r != 1)
 248             dev_urandom_exists = FALSE;
 249
 250           fclose (dev_urandom);
 251         }
 252       else
 253         dev_urandom_exists = FALSE;
 254     }
 255
 256   if (!dev_urandom_exists)
 257     {
 258       g_get_current_time (&now);
 259       seed[0] = now.tv_sec;
 260       seed[1] = now.tv_usec;
 261       seed[2] = getpid ();
 262       seed[3] = getppid ();
 263     }
 264 #else /* G_OS_WIN32 */
 265   /* rand_s() is only available since Visual Studio 2005 */
 266 #if defined(_MSC_VER) && _MSC_VER >= 1400
 267   gint i;
 268
 269   for (i = 0; i < G_N_ELEMENTS (seed); i++)
 270     rand_s (&seed[i]);
 271 #else
 272 #warning Using insecure seed for random number generation because of missing rand_s() in Windows XP
 273   GTimeVal now;
 274
 275   g_get_current_time (&now);
 276   seed[0] = now.tv_sec;
 277   seed[1] = now.tv_usec;
 278   seed[2] = getpid ();
 279   seed[3] = 0;
 280 #endif
 281
 282 #endif
 283
 284   return g_rand_new_with_seed_array (seed, 4);
 285 }
 286
 287 /**
 288  * g_rand_free:
 289  * @rand_: a #GRand
 290  *
 291  * Frees the memory allocated for the #GRand.
 292  */
 293 void
 294 g_rand_free (GRand *rand)
 295 {
 296   g_return_if_fail (rand != NULL);
 297
 298   g_free (rand);
 299 }
 300
 301 /**
 302  * g_rand_copy:
 303  * @rand_: a #GRand
 304  *
 305  * Copies a #GRand into a new one with the same exact state as before.
 306  * This way you can take a snapshot of the random number generator for
 307  * replaying later.
 308  *
 309  * Returns: the new #GRand
 310  *
 311  * Since: 2.4
 312  */
 313 GRand*
 314 g_rand_copy (GRand *rand)
 315 {
 316   GRand* new_rand;
 317
 318   g_return_val_if_fail (rand != NULL, NULL);
 319
 320   new_rand = g_new0 (GRand, 1);
 321   memcpy (new_rand, rand, sizeof (GRand));
 322
 323   return new_rand;
 324 }
 325
 326 /**
 327  * g_rand_set_seed:
 328  * @rand_: a #GRand
 329  * @seed: a value to reinitialize the random number generator
 330  *
 331  * Sets the seed for the random number generator #GRand to @seed.
 332  */
 333 void
 334 g_rand_set_seed (GRand   *rand,
 335                  guint32  seed)
 336 {
 337   g_return_if_fail (rand != NULL);
 338
 339   switch (get_random_version ())
 340     {
 341     case 20:
 342       /* setting initial seeds to mt[N] using         */
 343       /* the generator Line 25 of Table 1 in          */
 344       /* [KNUTH 1981, The Art of Computer Programming */
 345       /*    Vol. 2 (2nd Ed.), pp102]                  */
 346
 347       if (seed == 0) /* This would make the PRNG produce only zeros */
 348         seed = 0x6b842128; /* Just set it to another number */
 349
 350       rand->mt[0]= seed;
 351       for (rand->mti=1; rand->mti<N; rand->mti++)
 352         rand->mt[rand->mti] = (69069 * rand->mt[rand->mti-1]);
 353
 354       break;
 355     case 22:
 356       /* See Knuth TAOCP Vol2. 3rd Ed. P.106 for multiplier. */
 357       /* In the previous version (see above), MSBs of the    */
 358       /* seed affect only MSBs of the array mt[].            */
 359
 360       rand->mt[0]= seed;
 361       for (rand->mti=1; rand->mti<N; rand->mti++)
 362         rand->mt[rand->mti] = 1812433253UL *
 363           (rand->mt[rand->mti-1] ^ (rand->mt[rand->mti-1] >> 30)) + rand->mti;
 364       break;
 365     default:
 366       g_assert_not_reached ();
 367     }
 368 }
 369
 370 /**
 371  * g_rand_set_seed_array:
 372  * @rand_: a #GRand
 373  * @seed: array to initialize with
 374  * @seed_length: length of array
 375  *
 376  * Initializes the random number generator by an array of longs.
 377  * Array can be of arbitrary size, though only the first 624 values
 378  * are taken.  This function is useful if you have many low entropy
 379  * seeds, or if you require more then 32 bits of actual entropy for
 380  * your application.
 381  *
 382  * Since: 2.4
 383  */
 384 void
 385 g_rand_set_seed_array (GRand         *rand,
 386                        const guint32 *seed,
 387                        guint          seed_length)
 388 {
 389   int i, j, k;
 390
 391   g_return_if_fail (rand != NULL);
 392   g_return_if_fail (seed_length >= 1);
 393
 394   g_rand_set_seed (rand, 19650218UL);
 395
 396   i=1; j=0;
 397   k = (N>seed_length ? N : seed_length);
 398   for (; k; k--)
 399     {
 400       rand->mt[i] = (rand->mt[i] ^
 401                      ((rand->mt[i-1] ^ (rand->mt[i-1] >> 30)) * 1664525UL))
 402               + seed[j] + j; /* non linear */
 403       rand->mt[i] &= 0xffffffffUL; /* for WORDSIZE > 32 machines */
 404       i++; j++;
 405       if (i>=N)
 406         {
 407           rand->mt[0] = rand->mt[N-1];
 408           i=1;
 409         }
 410       if (j>=seed_length)
 411         j=0;
 412     }
 413   for (k=N-1; k; k--)
 414     {
 415       rand->mt[i] = (rand->mt[i] ^
 416                      ((rand->mt[i-1] ^ (rand->mt[i-1] >> 30)) * 1566083941UL))
 417               - i; /* non linear */
 418       rand->mt[i] &= 0xffffffffUL; /* for WORDSIZE > 32 machines */
 419       i++;
 420       if (i>=N)
 421         {
 422           rand->mt[0] = rand->mt[N-1];
 423           i=1;
 424         }
 425     }
 426
 427   rand->mt[0] = 0x80000000UL; /* MSB is 1; assuring non-zero initial array */
 428 }
 429
 430 /**
 431  * g_rand_boolean:
 432  * @rand_: a #GRand
 433  *
 434  * Returns a random #gboolean from @rand_.
 435  * This corresponds to a unbiased coin toss.
 436  *
 437  * Returns: a random #gboolean
 438  */
 439 /**
 440  * g_rand_int:
 441  * @rand_: a #GRand
 442  *
 443  * Returns the next random #guint32 from @rand_ equally distributed over
 444  * the range [0..2^32-1].
 445  *
 446  * Returns: a random number
 447  */
 448 guint32
 449 g_rand_int (GRand *rand)
 450 {
 451   guint32 y;
 452   static const guint32 mag01[2]={0x0, MATRIX_A};
 453   /* mag01[x] = x * MATRIX_A  for x=0,1 */
 454
 455   g_return_val_if_fail (rand != NULL, 0);
 456
 457   if (rand->mti >= N) { /* generate N words at one time */
 458     int kk;
 459
 460     for (kk = 0; kk < N - M; kk++) {
 461       y = (rand->mt[kk]&UPPER_MASK)|(rand->mt[kk+1]&LOWER_MASK);
 462       rand->mt[kk] = rand->mt[kk+M] ^ (y >> 1) ^ mag01[y & 0x1];
 463     }
 464     for (; kk < N - 1; kk++) {
 465       y = (rand->mt[kk]&UPPER_MASK)|(rand->mt[kk+1]&LOWER_MASK);
 466       rand->mt[kk] = rand->mt[kk+(M-N)] ^ (y >> 1) ^ mag01[y & 0x1];
 467     }
 468     y = (rand->mt[N-1]&UPPER_MASK)|(rand->mt[0]&LOWER_MASK);
 469     rand->mt[N-1] = rand->mt[M-1] ^ (y >> 1) ^ mag01[y & 0x1];
 470
 471     rand->mti = 0;
 472   }
 473
 474   y = rand->mt[rand->mti++];
 475   y ^= TEMPERING_SHIFT_U(y);
 476   y ^= TEMPERING_SHIFT_S(y) & TEMPERING_MASK_B;
 477   y ^= TEMPERING_SHIFT_T(y) & TEMPERING_MASK_C;
 478   y ^= TEMPERING_SHIFT_L(y);
 479
 480   return y;
 481 }
 482
 483 /* transform [0..2^32] -> [0..1] */
 484 #define G_RAND_DOUBLE_TRANSFORM 2.3283064365386962890625e-10
 485
 486 /**
 487  * g_rand_int_range:
 488  * @rand_: a #GRand
 489  * @begin: lower closed bound of the interval
 490  * @end: upper open bound of the interval
 491  *
 492  * Returns the next random #gint32 from @rand_ equally distributed over
 493  * the range [@begin..@end-1].
 494  *
 495  * Returns: a random number
 496  */
 497 gint32
 498 g_rand_int_range (GRand  *rand,
 499                   gint32  begin,
 500                   gint32  end)
 501 {
 502   guint32 dist = end - begin;
 503   guint32 random;
 504
 505   g_return_val_if_fail (rand != NULL, begin);
 506   g_return_val_if_fail (end > begin, begin);
 507
 508   switch (get_random_version ())
 509     {
 510     case 20:
 511       if (dist <= 0x10000L) /* 2^16 */
 512         {
 513           /* This method, which only calls g_rand_int once is only good
 514            * for (end - begin) <= 2^16, because we only have 32 bits set
 515            * from the one call to g_rand_int ().
 516            *
 517            * We are using (trans + trans * trans), because g_rand_int only
 518            * covers [0..2^32-1] and thus g_rand_int * trans only covers
 519            * [0..1-2^-32], but the biggest double < 1 is 1-2^-52.
 520            */
 521
 522           gdouble double_rand = g_rand_int (rand) *
 523             (G_RAND_DOUBLE_TRANSFORM +
 524              G_RAND_DOUBLE_TRANSFORM * G_RAND_DOUBLE_TRANSFORM);
 525
 526           random = (gint32) (double_rand * dist);
 527         }
 528       else
 529         {
 530           /* Now we use g_rand_double_range (), which will set 52 bits
 531            * for us, so that it is safe to round and still get a decent
 532            * distribution
 533            */
 534           random = (gint32) g_rand_double_range (rand, 0, dist);
 535         }
 536       break;
 537     case 22:
 538       if (dist == 0)
 539         random = 0;
 540       else
 541         {
 542           /* maxvalue is set to the predecessor of the greatest
 543            * multiple of dist less or equal 2^32.
 544            */
 545           guint32 maxvalue;
 546           if (dist <= 0x80000000u) /* 2^31 */
 547             {
 548               /* maxvalue = 2^32 - 1 - (2^32 % dist) */
 549               guint32 leftover = (0x80000000u % dist) * 2;
 550               if (leftover >= dist) leftover -= dist;
 551               maxvalue = 0xffffffffu - leftover;
 552             }
 553           else
 554             maxvalue = dist - 1;
 555
 556           do
 557             random = g_rand_int (rand);
 558           while (random > maxvalue);
 559
 560           random %= dist;
 561         }
 562       break;
 563     default:
 564       random = 0;               /* Quiet GCC */
 565       g_assert_not_reached ();
 566     }
 567
 568   return begin + random;
 569 }
 570
 571 /**
 572  * g_rand_double:
 573  * @rand_: a #GRand
 574  *
 575  * Returns the next random #gdouble from @rand_ equally distributed over
 576  * the range [0..1).
 577  *
 578  * Returns: a random number
 579  */
 580 gdouble
 581 g_rand_double (GRand *rand)
 582 {
 583   /* We set all 52 bits after the point for this, not only the first
 584      32. Thats why we need two calls to g_rand_int */
 585   gdouble retval = g_rand_int (rand) * G_RAND_DOUBLE_TRANSFORM;
 586   retval = (retval + g_rand_int (rand)) * G_RAND_DOUBLE_TRANSFORM;
 587
 588   /* The following might happen due to very bad rounding luck, but
 589    * actually this should be more than rare, we just try again then */
 590   if (retval >= 1.0)
 591     return g_rand_double (rand);
 592
 593   return retval;
 594 }
 595
 596 /**
 597  * g_rand_double_range:
 598  * @rand_: a #GRand
 599  * @begin: lower closed bound of the interval
 600  * @end: upper open bound of the interval
 601  *
 602  * Returns the next random #gdouble from @rand_ equally distributed over
 603  * the range [@begin..@end).
 604  *
 605  * Returns: a random number
 606  */
 607 gdouble
 608 g_rand_double_range (GRand   *rand,
 609                      gdouble  begin,
 610                      gdouble  end)
 611 {
 612   gdouble r;
 613
 614   r = g_rand_double (rand);
 615
 616   return r * end - (r - 1) * begin;
 617 }
 618
 619 static GRand *
 620 get_global_random (void)
 621 {
 622   static GRand *global_random;
 623
 624   /* called while locked */
 625   if (!global_random)
 626     global_random = g_rand_new ();
 627
 628   return global_random;
 629 }
 630
 631 /**
 632  * g_random_boolean:
 633  *
 634  * Returns a random #gboolean.
 635  * This corresponds to a unbiased coin toss.
 636  *
 637  * Returns: a random #gboolean
 638  */
 639 /**
 640  * g_random_int:
 641  *
 642  * Return a random #guint32 equally distributed over the range
 643  * [0..2^32-1].
 644  *
 645  * Returns: a random number
 646  */
 647 guint32
 648 g_random_int (void)
 649 {
 650   guint32 result;
 651   G_LOCK (global_random);
 652   result = g_rand_int (get_global_random ());
 653   G_UNLOCK (global_random);
 654   return result;
 655 }
 656
 657 /**
 658  * g_random_int_range:
 659  * @begin: lower closed bound of the interval
 660  * @end: upper open bound of the interval
 661  *
 662  * Returns a random #gint32 equally distributed over the range
 663  * [@begin..@end-1].
 664  *
 665  * Returns: a random number
 666  */
 667 gint32
 668 g_random_int_range (gint32 begin,
 669                     gint32 end)
 670 {
 671   gint32 result;
 672   G_LOCK (global_random);
 673   result = g_rand_int_range (get_global_random (), begin, end);
 674   G_UNLOCK (global_random);
 675   return result;
 676 }
 677
 678 /**
 679  * g_random_double:
 680  *
 681  * Returns a random #gdouble equally distributed over the range [0..1).
 682  *
 683  * Returns: a random number
 684  */
 685 gdouble
 686 g_random_double (void)
 687 {
 688   double result;
 689   G_LOCK (global_random);
 690   result = g_rand_double (get_global_random ());
 691   G_UNLOCK (global_random);
 692   return result;
 693 }
 694
 695 /**
 696  * g_random_double_range:
 697  * @begin: lower closed bound of the interval
 698  * @end: upper open bound of the interval
 699  *
 700  * Returns a random #gdouble equally distributed over the range
 701  * [@begin..@end).
 702  *
 703  * Returns: a random number
 704  */
 705 gdouble
 706 g_random_double_range (gdouble begin,
 707                        gdouble end)
 708 {
 709   double result;
 710   G_LOCK (global_random);
 711   result = g_rand_double_range (get_global_random (), begin, end);
 712   G_UNLOCK (global_random);
 713   return result;
 714 }
 715
 716 /**
 717  * g_random_set_seed:
 718  * @seed: a value to reinitialize the global random number generator
 719  *
 720  * Sets the seed for the global random number generator, which is used
 721  * by the g_random_* functions, to @seed.
 722  */
 723 void
 724 g_random_set_seed (guint32 seed)
 725 {
 726   G_LOCK (global_random);
 727   g_rand_set_seed (get_global_random (), seed);
 728   G_UNLOCK (global_random);
 729 }