stdlib/tst-random.c

   1 /* Test program for random(), srandom(), initstate(), setstate()
   2    Placed in the public domain.  */
   3
   4 /* This program primarily tests the correct functioning of srandom()
   5    and setstate().  The strategy is generate and store a set of random
   6    sequences, each with a specified starting seed.  Then each sequence
   7    is regenerated twice and checked against the stored values.
   8
   9    First they are regenerated one sequence at a time, using srandom()
  10    to set the initial state.  A discrepancy here would suggest that
  11    srandom() was failing to completely initialize the random number
  12    generator.
  13
  14    Second the sequences are regenerated in an interleaved order.
  15    A state vector is created for each sequence using initstate().
  16    setstate() is used to switch from sequence to sequence during
  17    the interleaved generation.  A discrepancy here would suggest
  18    a problem with either initstate() failing to initialize the
  19    random number generator properly, or the failure of setstate()
  20    to correctly save and restore state information.  Also, each
  21    time setstate() is called, the returned value is checked for
  22    correctness (since we know what it should be).
  23
  24    Note:  We use default state vector for sequence 0 and our own
  25    state vectors for the remaining sequences.  This is to give a check
  26    that the value returned by initstate() is valid and can indeed be
  27    used in the future.  */
  28
  29 /* Strategy:
  30    1.  Use srandom() followed by calls on random to generate a set of
  31        sequences of values.
  32    2.  Regenerate and check the sequences.
  33    3.  Use initstate() to create new states.
  34    4.  Regenerate the sequences in an interleaved manner and check.
  35 */
  36
  37 #include <stdlib.h>
  38 #include <stdio.h>
  39
  40 const int degree = 128;         /* random number generator degree (should
  41                                    be one of 8, 16, 32, 64, 128, 256) */
  42 const int nseq = 3;             /* number of test sequences */
  43 const int nrnd = 50;            /* length of each test sequence */
  44 const unsigned int seed[3] = { 0x12344321U, 0xEE11DD22U, 0xFEDCBA98 };
  45
  46 void fail (const char *msg, int s, int i) __attribute__ ((__noreturn__));
  47
  48 static int
  49 do_test (void)
  50 {
  51   long int rnd[nseq][nrnd];     /* pseudorandom numbers */
  52   char* state[nseq];            /* state for PRNG */
  53   char* oldstate[nseq];         /* old PRNG state */
  54   int s;                        /* sequence index */
  55   int i;                        /* element index */
  56
  57   printf ("Beginning random package test using %d sequences of length %d.\n",
  58           nseq, nrnd);
  59
  60   /* 1. Generate and store the sequences.  */
  61   printf ("Generating random sequences.\n");
  62   for (s = 0; s < nseq; ++s)
  63     {
  64       srandom ( seed[s] );
  65       for (i = 0; i < nrnd; ++i)
  66         rnd[s][i] = random ();
  67     }
  68
  69   /* 2. Regenerate and check.  */
  70   printf ("Regenerating and checking sequences.\n");
  71   for (s = 0; s < nseq; ++s)
  72     {
  73       srandom (seed[s]);
  74       for (i = 0; i < nrnd; ++i)
  75         if (rnd[s][i] != random ())
  76           fail ("first regenerate test", s, i);
  77     }
  78
  79   /* 3. Create state vector, one for each sequence.
  80         First state is random's internal state; others are malloced.  */
  81   printf ("Creating and checking state vector for each sequence.\n");
  82   srandom (seed[0]);                    /* reseed with first seed */
  83   for (s = 1; s < nseq; ++s)
  84     {
  85       state[s] = (char*) malloc (degree);
  86       oldstate[s] = initstate (seed[s], state[s], degree);
  87     }
  88   state[0] = oldstate[1];
  89
  90   /* Check returned values.  */
  91   for (s = 1; s < nseq - 1; ++s)
  92     if (state[s] != oldstate[s + 1])
  93       fail ("bad initstate() return value", s, i);
  94
  95   /* 4. Regenerate sequences interleaved and check.  */
  96   printf ("Regenerating and checking sequences in interleaved order.\n");
  97   for (i = 0; i < nrnd; ++i)
  98     {
  99       for (s = 0; s < nseq; ++s)
 100         {
 101           char *oldstate = (char *) setstate (state[s]);
 102           if (oldstate != state[(s + nseq - 1) % nseq])
 103             fail ("bad setstate() return value", s, i);
 104           if (rnd[s][i] != random ())
 105             fail ("bad value generated in interleave test", s, i);
 106         }
 107     }
 108   printf ("All tests passed!\n");
 109   return 0;
 110 }
 111
 112 void
 113 fail (const char *msg, int s, int i)
 114 {
 115   printf ("\nTest FAILED: ");
 116   printf ("%s (seq %d, pos %d).\n", msg, s, i);
 117   exit (1);
 118 }
 119
 120 #define TEST_FUNCTION do_test ()
 121 #include "../test-skeleton.c"