random.c

Functions

coin_toss         X
get_rand          X
rand_percent      X
rrandom           X
srrandom          X

   1: #ifndef lint
   2: static char sccsid[] = "@(#)random.c	5.1 (Berkeley) 11/25/87";
   3: #endif /* not lint */
   4: 
   5: static long rntb[32] = {
   6:              3, 0x9a319039, 0x32d9c024, 0x9b663182, 0x5da1f342,
   7:     0xde3b81e0, 0xdf0a6fb5, 0xf103bc02, 0x48f340fb, 0x7449e56b,
   8:     0xbeb1dbb0, 0xab5c5918, 0x946554fd, 0x8c2e680f, 0xeb3d799f,
   9:     0xb11ee0b7, 0x2d436b86, 0xda672e2a, 0x1588ca88, 0xe369735d,
  10:     0x904f35f7, 0xd7158fd6, 0x6fa6f051, 0x616e6b96, 0xac94efdc,
  11:     0x36413f93, 0xc622c298, 0xf5a42ab8, 0x8a88d77b, 0xf5ad9d0e,
  12:     0x8999220b, 0x27fb47b9
  13: };
  14: 
  15: static long *fptr = &rntb[4];
  16: static long *rptr = &rntb[1];
  17: static long *state = &rntb[1];
  18: static int rand_type = 3;
  19: static int rand_deg = 31;
  20: static int rand_sep = 3;
  21: static long *end_ptr = &rntb[32];
  22: 
  23: srrandom(x)
  24: int x;
  25: {
  26:     register int i;
  27:     long rrandom();
  28: 
  29:     state[0] = (long) x;
  30:     if (rand_type != 0) {
  31:         for (i = 1; i < rand_deg; i++) {
  32:             state[i] = 1103515245 * state[i - 1] + 12345;
  33:         }
  34:         fptr = &state[rand_sep];
  35:         rptr = &state[0];
  36:         for (i = 0; i < 10 * rand_deg; i++) {
  37:             (void) rrandom();
  38:         }
  39:     }
  40: }
  41: 
  42: long
  43: rrandom()
  44: {
  45:     long i;
  46: 
  47:     if (rand_type == 0) {
  48:         i = state[0] = (state[0]*1103515245 + 12345) & 0x7fffffff;
  49:     } else {
  50:         *fptr += *rptr;
  51:         i = (*fptr >> 1) & 0x7fffffff;
  52:         if (++fptr >= end_ptr) {
  53:             fptr = state;
  54:             ++rptr;
  55:         } else {
  56:             if (++rptr >= end_ptr) {
  57:                 rptr = state;
  58:             }
  59:         }
  60:     }
  61:     return(i);
  62: }
  63: 
  64: get_rand(x, y)
  65: register int x, y;
  66: {
  67:     register int r, t;
  68:     long lr;
  69: 
  70:     if (x > y) {
  71:         t = y;
  72:         y = x;
  73:         x = t;
  74:     }
  75:     lr = rrandom();
  76:     lr &= (long) 0x00003fff;
  77:     r = (int) lr;
  78:     r = (r % ((y - x) + 1)) + x;
  79:     return(r);
  80: }
  81: 
  82: rand_percent(percentage)
  83: register int percentage;
  84: {
  85:     return(get_rand(1, 100) <= percentage);
  86: }
  87: 
  88: coin_toss()
  89: {
  90: 
  91:     return(((rrandom() & 01) ? 1 : 0));
  92: }