random.c

   1 /**********************************************************************
   2
   3   random.c -
   4
   5   $Author$
   6   created at: Fri Dec 24 16:39:21 JST 1993
   7
   8   Copyright (C) 1993-2007 Yukihiro Matsumoto
   9
  10 **********************************************************************/
  11
  12 /*
  13 This is based on trimmed version of MT19937.  To get the original version,
  14 contact <http://www.math.sci.hiroshima-u.ac.jp/~m-mat/MT/emt.html>.
  15
  16 The original copyright notice follows.
  17
  18    A C-program for MT19937, with initialization improved 2002/2/10.
  19    Coded by Takuji Nishimura and Makoto Matsumoto.
  20    This is a faster version by taking Shawn Cokus's optimization,
  21    Matthe Bellew's simplification, Isaku Wada's real version.
  22
  23    Before using, initialize the state by using init_genrand(mt, seed)
  24    or init_by_array(mt, init_key, key_length).
  25
  26    Copyright (C) 1997 - 2002, Makoto Matsumoto and Takuji Nishimura,
  27    All rights reserved.
  28
  29    Redistribution and use in source and binary forms, with or without
  30    modification, are permitted provided that the following conditions
  31    are met:
  32
  33      1. Redistributions of source code must retain the above copyright
  34         notice, this list of conditions and the following disclaimer.
  35
  36      2. Redistributions in binary form must reproduce the above copyright
  37         notice, this list of conditions and the following disclaimer in the
  38         documentation and/or other materials provided with the distribution.
  39
  40      3. The names of its contributors may not be used to endorse or promote
  41         products derived from this software without specific prior written
  42         permission.
  43
  44    THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  45    "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  46    LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR
  47    A PARTICULAR PURPOSE ARE DISCLAIMED.  IN NO EVENT SHALL THE COPYRIGHT OWNER OR
  48    CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL,
  49    EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO,
  50    PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR
  51    PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF
  52    LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING
  53    NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT OF THE USE OF THIS
  54    SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
  55
  56
  57    Any feedback is very welcome.
  58    http://www.math.keio.ac.jp/matumoto/emt.html
  59    email: matumoto@math.keio.ac.jp
  60 */
  61
  62 /* Period parameters */
  63 #define N 624
  64 #define M 397
  65 #define MATRIX_A 0x9908b0dfUL   /* constant vector a */
  66 #define UMASK 0x80000000UL /* most significant w-r bits */
  67 #define LMASK 0x7fffffffUL /* least significant r bits */
  68 #define MIXBITS(u,v) ( ((u) & UMASK) | ((v) & LMASK) )
  69 #define TWIST(u,v) ((MIXBITS(u,v) >> 1) ^ ((v)&1UL ? MATRIX_A : 0UL))
  70
  71 struct MT {
  72     unsigned long state[N]; /* the array for the state vector  */
  73     unsigned long *next;
  74     int left;
  75 };
  76
  77 #define genrand_initialized(mt) ((mt)->next != 0)
  78 #define uninit_genrand(mt) ((mt)->next = 0)
  79
  80 /* initializes state[N] with a seed */
  81 static void
  82 init_genrand(struct MT *mt, unsigned long s)
  83 {
  84     int j;
  85     mt->state[0] = s & 0xffffffffUL;
  86     for (j=1; j<N; j++) {
  87         mt->state[j] = (1812433253UL * (mt->state[j-1] ^ (mt->state[j-1] >> 30)) + j);
  88         /* See Knuth TAOCP Vol2. 3rd Ed. P.106 for multiplier. */
  89         /* In the previous versions, MSBs of the seed affect   */
  90         /* only MSBs of the array state[].                        */
  91         /* 2002/01/09 modified by Makoto Matsumoto             */
  92         mt->state[j] &= 0xffffffffUL;  /* for >32 bit machines */
  93     }
  94     mt->left = 1;
  95     mt->next = mt->state + N - 1;
  96 }
  97
  98 /* initialize by an array with array-length */
  99 /* init_key is the array for initializing keys */
 100 /* key_length is its length */
 101 /* slight change for C++, 2004/2/26 */
 102 static void
 103 init_by_array(struct MT *mt, unsigned long init_key[], int key_length)
 104 {
 105     int i, j, k;
 106     init_genrand(mt, 19650218UL);
 107     i=1; j=0;
 108     k = (N>key_length ? N : key_length);
 109     for (; k; k--) {
 110         mt->state[i] = (mt->state[i] ^ ((mt->state[i-1] ^ (mt->state[i-1] >> 30)) * 1664525UL))
 111           + init_key[j] + j; /* non linear */
 112         mt->state[i] &= 0xffffffffUL; /* for WORDSIZE > 32 machines */
 113         i++; j++;
 114         if (i>=N) { mt->state[0] = mt->state[N-1]; i=1; }
 115         if (j>=key_length) j=0;
 116     }
 117     for (k=N-1; k; k--) {
 118         mt->state[i] = (mt->state[i] ^ ((mt->state[i-1] ^ (mt->state[i-1] >> 30)) * 1566083941UL))
 119           - i; /* non linear */
 120         mt->state[i] &= 0xffffffffUL; /* for WORDSIZE > 32 machines */
 121         i++;
 122         if (i>=N) { mt->state[0] = mt->state[N-1]; i=1; }
 123     }
 124
 125     mt->state[0] = 0x80000000UL; /* MSB is 1; assuring non-zero initial array */
 126 }
 127
 128 static void
 129 next_state(struct MT *mt)
 130 {
 131     unsigned long *p = mt->state;
 132     int j;
 133
 134     /* if init_genrand() has not been called, */
 135     /* a default initial seed is used         */
 136     if (!genrand_initialized(mt)) init_genrand(mt, 5489UL);
 137
 138     mt->left = N;
 139     mt->next = mt->state;
 140
 141     for (j=N-M+1; --j; p++)
 142         *p = p[M] ^ TWIST(p[0], p[1]);
 143
 144     for (j=M; --j; p++)
 145         *p = p[M-N] ^ TWIST(p[0], p[1]);
 146
 147     *p = p[M-N] ^ TWIST(p[0], mt->state[0]);
 148 }
 149
 150 /* generates a random number on [0,0xffffffff]-interval */
 151 static unsigned long
 152 genrand_int32(struct MT *mt)
 153 {
 154     unsigned long y;
 155
 156     if (--mt->left <= 0) next_state(mt);
 157     y = *mt->next++;
 158
 159     /* Tempering */
 160     y ^= (y >> 11);
 161     y ^= (y << 7) & 0x9d2c5680UL;
 162     y ^= (y << 15) & 0xefc60000UL;
 163     y ^= (y >> 18);
 164
 165     return y;
 166 }
 167
 168 /* generates a random number on [0,1) with 53-bit resolution*/
 169 static double
 170 genrand_real(struct MT *mt)
 171 {
 172     unsigned long a=genrand_int32(mt)>>5, b=genrand_int32(mt)>>6;
 173     return(a*67108864.0+b)*(1.0/9007199254740992.0);
 174 }
 175 /* These real versions are due to Isaku Wada, 2002/01/09 added */
 176
 177 #undef N
 178 #undef M
 179
 180 /* These real versions are due to Isaku Wada, 2002/01/09 added */
 181
 182 #include "ruby/ruby.h"
 183
 184 #ifdef HAVE_UNISTD_H
 185 #include <unistd.h>
 186 #endif
 187 #include <time.h>
 188 #include <sys/types.h>
 189 #include <sys/stat.h>
 190 #ifdef HAVE_FCNTL_H
 191 #include <fcntl.h>
 192 #endif
 193
 194 #define DEFAULT_SEED_CNT 4
 195
 196 struct RandSeed {
 197     VALUE value;
 198     unsigned long initial[DEFAULT_SEED_CNT];
 199 };
 200
 201 struct Random {
 202     struct MT mt;
 203     struct RandSeed seed;
 204 };
 205
 206 static struct Random default_mt;
 207
 208 unsigned long
 209 rb_genrand_int32(void)
 210 {
 211     return genrand_int32(&default_mt.mt);
 212 }
 213
 214 double
 215 rb_genrand_real(void)
 216 {
 217     return genrand_real(&default_mt.mt);
 218 }
 219
 220 static VALUE
 221 rand_init(struct MT *mt, VALUE vseed)
 222 {
 223     volatile VALUE seed;
 224     long len;
 225     unsigned long *buf;
 226
 227     seed = rb_to_int(vseed);
 228     switch (TYPE(seed)) {
 229       case T_FIXNUM:
 230           len = sizeof(VALUE);
 231           break;
 232       case T_BIGNUM:
 233           len = RBIGNUM_LEN(seed) * SIZEOF_BDIGITS;
 234           if (len == 0)
 235               len = 4;
 236           break;
 237       default:
 238           rb_raise(rb_eTypeError, "failed to convert %s into Integer",
 239                    rb_obj_classname(vseed));
 240     }
 241     len = (len + 3) / 4; /* number of 32bit words */
 242     buf = ALLOC_N(unsigned long, len); /* allocate longs for init_by_array */
 243     memset(buf, 0, len * sizeof(long));
 244     if (FIXNUM_P(seed)) {
 245         buf[0] = FIX2ULONG(seed) & 0xffffffff;
 246 #if SIZEOF_LONG > 4
 247         buf[1] = FIX2ULONG(seed) >> 32;
 248 #endif
 249     }
 250     else {
 251         int i, j;
 252         for (i = RBIGNUM_LEN(seed)-1; 0 <= i; i--) {
 253             j = i * SIZEOF_BDIGITS / 4;
 254 #if SIZEOF_BDIGITS < 4
 255             buf[j] <<= SIZEOF_BDIGITS * 8;
 256 #endif
 257             buf[j] |= RBIGNUM_DIGITS(seed)[i];
 258         }
 259     }
 260     while (1 < len && buf[len-1] == 0) {
 261         len--;
 262     }
 263     if (len <= 1) {
 264         init_genrand(mt, buf[0]);
 265     }
 266     else {
 267         if (buf[len-1] == 1) /* remove leading-zero-guard */
 268             len--;
 269         init_by_array(mt, buf, len);
 270     }
 271     xfree(buf);
 272     return seed;
 273 }
 274
 275 #define DEFAULT_SEED_LEN (DEFAULT_SEED_CNT * sizeof(long))
 276
 277 static void
 278 fill_random_seed(unsigned long seed[DEFAULT_SEED_CNT])
 279 {
 280     static int n = 0;
 281     struct timeval tv;
 282     int fd;
 283     struct stat statbuf;
 284
 285     memset(seed, 0, DEFAULT_SEED_LEN);
 286
 287 #ifdef S_ISCHR
 288     if ((fd = open("/dev/urandom", O_RDONLY
 289 #ifdef O_NONBLOCK
 290             |O_NONBLOCK
 291 #endif
 292 #ifdef O_NOCTTY
 293             |O_NOCTTY
 294 #endif
 295 #ifdef O_NOFOLLOW
 296             |O_NOFOLLOW
 297 #endif
 298             )) >= 0) {
 299         if (fstat(fd, &statbuf) == 0 && S_ISCHR(statbuf.st_mode)) {
 300             read(fd, seed, DEFAULT_SEED_LEN);
 301         }
 302         close(fd);
 303     }
 304 #endif
 305
 306     gettimeofday(&tv, 0);
 307     seed[0] ^= tv.tv_usec;
 308     seed[1] ^= tv.tv_sec;
 309     seed[2] ^= getpid() ^ (n++ << 16);
 310     seed[3] ^= (unsigned long)&seed;
 311 }
 312
 313 static VALUE
 314 make_seed_value(const void *ptr)
 315 {
 316     BDIGIT *digits;
 317     NEWOBJ(big, struct RBignum);
 318     OBJSETUP(big, rb_cBignum, T_BIGNUM);
 319
 320     RBIGNUM_SET_SIGN(big, 1);
 321     rb_big_resize((VALUE)big, DEFAULT_SEED_LEN / SIZEOF_BDIGITS + 1);
 322     digits = RBIGNUM_DIGITS(big);
 323
 324     MEMCPY((char *)RBIGNUM_DIGITS(big), ptr, char, DEFAULT_SEED_LEN);
 325
 326     /* set leading-zero-guard if need. */
 327     digits[RBIGNUM_LEN(big)-1] = digits[RBIGNUM_LEN(big)-2] <= 1 ? 1 : 0;
 328
 329     return rb_big_norm((VALUE)big);
 330 }
 331
 332 static VALUE
 333 random_seed(void)
 334 {
 335     unsigned long buf[DEFAULT_SEED_CNT];
 336     fill_random_seed(buf);
 337     return make_seed_value(buf);
 338 }
 339
 340 /*
 341  *  call-seq:
 342  *     srand(number=0)    => old_seed
 343  *
 344  *  Seeds the pseudorandom number generator to the value of
 345  *  <i>number</i>.<code>to_i.abs</code>. If <i>number</i> is omitted
 346  *  or zero, seeds the generator using a combination of the time, the
 347  *  process id, and a sequence number. (This is also the behavior if
 348  *  <code>Kernel::rand</code> is called without previously calling
 349  *  <code>srand</code>, but without the sequence.) By setting the seed
 350  *  to a known value, scripts can be made deterministic during testing.
 351  *  The previous seed value is returned. Also see <code>Kernel::rand</code>.
 352  */
 353
 354 static VALUE
 355 rb_f_srand(int argc, VALUE *argv, VALUE obj)
 356 {
 357     VALUE seed, old;
 358
 359     rb_secure(4);
 360     if (argc == 0) {
 361         seed = random_seed();
 362     }
 363     else {
 364         rb_scan_args(argc, argv, "01", &seed);
 365     }
 366     old = default_mt.seed.value;
 367     default_mt.seed.value = rand_init(&default_mt.mt, seed);
 368
 369     return old;
 370 }
 371
 372 static unsigned long
 373 make_mask(unsigned long x)
 374 {
 375     x = x | x >> 1;
 376     x = x | x >> 2;
 377     x = x | x >> 4;
 378     x = x | x >> 8;
 379     x = x | x >> 16;
 380 #if 4 < SIZEOF_LONG
 381     x = x | x >> 32;
 382 #endif
 383     return x;
 384 }
 385
 386 static unsigned long
 387 limited_rand(struct MT *mt, unsigned long limit)
 388 {
 389     unsigned long mask = make_mask(limit);
 390     int i;
 391     unsigned long val;
 392
 393   retry:
 394     val = 0;
 395     for (i = SIZEOF_LONG/4-1; 0 <= i; i--) {
 396         if (mask >> (i * 32)) {
 397             val |= genrand_int32(mt) << (i * 32);
 398             val &= mask;
 399             if (limit < val)
 400                 goto retry;
 401         }
 402     }
 403     return val;
 404 }
 405
 406 static VALUE
 407 limited_big_rand(struct MT *mt, struct RBignum *limit)
 408 {
 409     unsigned long mask, lim, rnd;
 410     struct RBignum *val;
 411     int i, len, boundary;
 412
 413     len = (RBIGNUM_LEN(limit) * SIZEOF_BDIGITS + 3) / 4;
 414     val = (struct RBignum *)rb_big_clone((VALUE)limit);
 415     RBIGNUM_SET_SIGN(val, 1);
 416 #if SIZEOF_BDIGITS == 2
 417 # define BIG_GET32(big,i) \
 418     (RBIGNUM_DIGITS(big)[(i)*2] | \
 419      ((i)*2+1 < RBIGNUM_LEN(big) ? \
 420       (RBIGNUM_DIGITS(big)[(i)*2+1] << 16) : \
 421       0))
 422 # define BIG_SET32(big,i,d) \
 423     ((RBIGNUM_DIGITS(big)[(i)*2] = (d) & 0xffff), \
 424      ((i)*2+1 < RBIGNUM_LEN(big) ? \
 425       (RBIGNUM_DIGITS(big)[(i)*2+1] = (d) >> 16) : \
 426       0))
 427 #else
 428     /* SIZEOF_BDIGITS == 4 */
 429 # define BIG_GET32(big,i) (RBIGNUM_DIGITS(big)[i])
 430 # define BIG_SET32(big,i,d) (RBIGNUM_DIGITS(big)[i] = (d))
 431 #endif
 432   retry:
 433     mask = 0;
 434     boundary = 1;
 435     for (i = len-1; 0 <= i; i--) {
 436         lim = BIG_GET32(limit, i);
 437         mask = mask ? 0xffffffff : make_mask(lim);
 438         if (mask) {
 439             rnd = genrand_int32(mt) & mask;
 440             if (boundary) {
 441                 if (lim < rnd)
 442                     goto retry;
 443                 if (rnd < lim)
 444                     boundary = 0;
 445             }
 446         }
 447         else {
 448             rnd = 0;
 449         }
 450         BIG_SET32(val, i, rnd);
 451     }
 452     return rb_big_norm((VALUE)val);
 453 }
 454
 455 /*
 456  *  call-seq:
 457  *     rand(max=0)    => number
 458  *
 459  *  Converts <i>max</i> to an integer using max1 =
 460  *  max<code>.to_i.abs</code>. If the result is zero, returns a
 461  *  pseudorandom floating point number greater than or equal to 0.0 and
 462  *  less than 1.0. Otherwise, returns a pseudorandom integer greater
 463  *  than or equal to zero and less than max1. <code>Kernel::srand</code>
 464  *  may be used to ensure repeatable sequences of random numbers between
 465  *  different runs of the program. Ruby currently uses a modified
 466  *  Mersenne Twister with a period of 2**19937-1.
 467  *
 468  *     srand 1234                 #=> 0
 469  *     [ rand,  rand ]            #=> [0.191519450163469, 0.49766366626136]
 470  *     [ rand(10), rand(1000) ]   #=> [6, 817]
 471  *     srand 1234                 #=> 1234
 472  *     [ rand,  rand ]            #=> [0.191519450163469, 0.49766366626136]
 473  */
 474
 475 static VALUE
 476 rb_f_rand(int argc, VALUE *argv, VALUE obj)
 477 {
 478     VALUE vmax;
 479     long val, max;
 480     struct MT *mt = &default_mt.mt;
 481
 482     rb_scan_args(argc, argv, "01", &vmax);
 483     if (!genrand_initialized(mt)) {
 484         rand_init(mt, random_seed());
 485     }
 486     switch (TYPE(vmax)) {
 487       case T_FLOAT:
 488         if (RFLOAT_VALUE(vmax) <= LONG_MAX && RFLOAT_VALUE(vmax) >= LONG_MIN) {
 489             max = (long)RFLOAT_VALUE(vmax);
 490             break;
 491         }
 492         if (RFLOAT_VALUE(vmax) < 0)
 493             vmax = rb_dbl2big(-RFLOAT_VALUE(vmax));
 494         else
 495             vmax = rb_dbl2big(RFLOAT_VALUE(vmax));
 496         /* fall through */
 497       case T_BIGNUM:
 498       bignum:
 499         {
 500             struct RBignum *limit = (struct RBignum *)vmax;
 501             if (!RBIGNUM_SIGN(limit)) {
 502                 limit = (struct RBignum *)rb_big_clone(vmax);
 503                 RBIGNUM_SET_SIGN(limit, 1);
 504             }
 505             limit = (struct RBignum *)rb_big_minus((VALUE)limit, INT2FIX(1));
 506             if (FIXNUM_P((VALUE)limit)) {
 507                 if (FIX2LONG((VALUE)limit) == -1)
 508                     return DOUBLE2NUM(genrand_real(mt));
 509                 return LONG2NUM(limited_rand(mt, FIX2LONG((VALUE)limit)));
 510             }
 511             return limited_big_rand(mt, limit);
 512         }
 513       case T_NIL:
 514         max = 0;
 515         break;
 516       default:
 517         vmax = rb_Integer(vmax);
 518         if (TYPE(vmax) == T_BIGNUM) goto bignum;
 519       case T_FIXNUM:
 520         max = FIX2LONG(vmax);
 521         break;
 522     }
 523
 524     if (max == 0) {
 525         return DOUBLE2NUM(genrand_real(mt));
 526     }
 527     if (max < 0) max = -max;
 528     val = limited_rand(mt, max-1);
 529     return LONG2NUM(val);
 530 }
 531
 532 void
 533 Init_RandomSeed(void)
 534 {
 535     fill_random_seed(default_mt.seed.initial);
 536     init_by_array(&default_mt.mt, default_mt.seed.initial, DEFAULT_SEED_CNT);
 537 }
 538
 539 static void
 540 Init_RandomSeed2(void)
 541 {
 542     default_mt.seed.value = make_seed_value(default_mt.seed.initial);
 543     memset(default_mt.seed.initial, 0, DEFAULT_SEED_LEN);
 544 }
 545
 546 void
 547 rb_reset_random_seed(void)
 548 {
 549     uninit_genrand(&default_mt.mt);
 550     default_mt.seed.value = INT2FIX(0);
 551 }
 552
 553 void
 554 Init_Random(void)
 555 {
 556     Init_RandomSeed2();
 557     rb_define_global_function("srand", rb_f_srand, -1);
 558     rb_define_global_function("rand", rb_f_rand, -1);
 559     rb_global_variable(&default_mt.seed.value);
 560 }