src/functional/random.c

   1 #define _XOPEN_SOURCE 700
   2 #include <stdio.h>
   3 #include <stdlib.h>
   4 #include "test.h"
   5
   6 /* naive statistical checks */
   7
   8 /* error p ~ 1.6e-6 */
   9 static int chkmissing(long *x)
  10 {
  11         int d[8] = {0};
  12         int i;
  13         for (i = 0; i < 100; i++)
  14                 d[x[i]%8]++;
  15         for (i = 0; i < 8; i++)
  16                 if (d[i]==0)
  17                         return 1;
  18         return 0;
  19 }
  20
  21 /* error p ~ 4e-6 */
  22 static int chkrepeat(long *x)
  23 {
  24         int i, j;
  25         for (i = 0; i < 100; i++)
  26                 for (j = 0; j < i; j++)
  27                         if (x[i] == x[j])
  28                                 return 1;
  29         return 0;
  30 }
  31
  32 /* error p ~ 1e-6 */
  33 static unsigned orx;
  34 static int chkones(long *x)
  35 {
  36         int i;
  37         orx = 0;
  38         for (i = 0; i < 20; i++)
  39                 orx |= x[i];
  40         return orx != 0x7fffffff;
  41 }
  42
  43 void checkseed(unsigned seed, long *x)
  44 {
  45         int i;
  46         srandom(seed);
  47         for (i = 0; i < 100; i++)
  48                 x[i] = random();
  49         if (chkmissing(x))
  50                 t_error("weak seed %d, missing pattern in low bits\n", seed);
  51         if (chkrepeat(x))
  52                 t_error("weak seed %d, exact repeats\n", seed);
  53         if (chkones(x))
  54                 t_error("weak seed %d, or pattern: 0x%08x\n", seed, orx);
  55 }
  56
  57 int main()
  58 {
  59         long x[100];
  60         long y,z;
  61         int i;
  62         char state[128];
  63         char *p;
  64         char *q;
  65
  66         for (i = 0; i < 100; i++)
  67                 x[i] = random();
  68         p = initstate(1, state, sizeof state);
  69         for (i = 0; i < 100; i++)
  70                 if (x[i] != (y = random()))
  71                         t_error("initstate(1) is not default: (%d) default: %ld, seed1: %ld\n", i, x[i], y);
  72         for (i = 0; i < 10; i++) {
  73                 z = random();
  74                 q = setstate(p);
  75                 if (z != (y = random()))
  76                         t_error("setstate failed (%d) orig: %ld, reset: %ld\n", i, z, y);
  77                 p = setstate(q);
  78         }
  79         srandom(1);
  80         for (i = 0; i < 100; i++)
  81                 if (x[i] != (y = random()))
  82                         t_error("srandom(1) is not default: (%d) default: %ld, seed1: %ld\n", i, x[i], y);
  83         checkseed(0x7fffffff, x);
  84         for (i = 0; i < 10; i++)
  85                 checkseed(i, x);
  86         return t_status;
  87 }