simple random test (statistical with very low failure probability)

diff --git a/src/functional/random.c b/src/functional/random.c
new file mode 100644 (file)
index 0000000..65bbf28
--- /dev/null
+++ b/src/functional/random.c
@@ -0,0 +1,86 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include "test.h"
+
+/* naive statistical checks */
+
+/* error p ~ 1.6e-6 */
+static int chkmissing(long *x)
+{
+       int d[8] = {0};
+       int i;
+       for (i = 0; i < 100; i++)
+               d[x[i]%8]++;
+       for (i = 0; i < 8; i++)
+               if (d[i]==0)
+                       return 1;
+       return 0;
+}
+
+/* error p ~ 4e-6 */
+static int chkrepeat(long *x)
+{
+       int i, j;
+       for (i = 0; i < 100; i++)
+               for (j = 0; j < i; j++)
+                       if (x[i] == x[j])
+                               return 1;
+       return 0;
+}
+
+/* error p ~ 1e-6 */
+static unsigned orx;
+static int chkones(long *x)
+{
+       int i;
+       orx = 0;
+       for (i = 0; i < 20; i++)
+               orx |= x[i];
+       return orx != 0x7fffffff;
+}
+
+void checkseed(unsigned seed, long *x)
+{
+       int i;
+       srandom(seed);
+       for (i = 0; i < 100; i++)
+               x[i] = random();
+       if (chkmissing(x))
+               t_error("weak seed %d, missing pattern in low bits\n", seed);
+       if (chkrepeat(x))
+               t_error("weak seed %d, exact repeats\n", seed);
+       if (chkones(x))
+               t_error("weak seed %d, or pattern: 0x%08x\n", seed, orx);
+}
+
+int main()
+{
+       long x[100];
+       long y,z;
+       int i;
+       char state[128];
+       char *p;
+       char *q;
+
+       for (i = 0; i < 100; i++)
+               x[i] = random();
+       p = initstate(1, state, sizeof state);
+       for (i = 0; i < 100; i++)
+               if (x[i] != (y = random()))
+                       t_error("initstate(1) is not default: (%d) default: %ld, seed1: %ld\n", i, x[i], y);
+       for (i = 0; i < 10; i++) {
+               z = random();
+               q = setstate(p);
+               if (z != (y = random()))
+                       t_error("setstate failed (%d) orig: %ld, reset: %ld\n", i, z, y);
+               p = setstate(q);
+       }
+       srandom(1);
+       for (i = 0; i < 100; i++)
+               if (x[i] != (y = random()))
+                       t_error("srandom(1) is not default: (%d) default: %ld, seed1: %ld\n", i, x[i], y);
+       checkseed(0x7fffffff, x);
+       for (i = 0; i < 10; i++)
+               checkseed(i, x);
+       return t_status;
+}