Fix portability bug in get_normal_pair (RAND_MAX != MAX_RANDOM_VALUE).

Also try to improve readability and performance.

diff --git a/contrib/tablefunc/tablefunc.c b/contrib/tablefunc/tablefunc.c
index 875e340c29e18af822a6aa135ce71ca1ba85445f..f5ac0f8ee6790029b8cf9765cc5f5e71a4e7fe22 100644 (file)
--- a/contrib/tablefunc/tablefunc.c
+++ b/contrib/tablefunc/tablefunc.c
@@ -224,31 +224,27 @@ get_normal_pair(float8 *x1, float8 *x2)
                                v2,
                                s;
 
-       for (;;)
+       do
        {
-               u1 = (float8) random() / (float8) RAND_MAX;
-               u2 = (float8) random() / (float8) RAND_MAX;
+               u1 = (float8) random() / (float8) MAX_RANDOM_VALUE;
+               u2 = (float8) random() / (float8) MAX_RANDOM_VALUE;
 
                v1 = (2.0 * u1) - 1.0;
                v2 = (2.0 * u2) - 1.0;
 
-               s = pow(v1, 2) + pow(v2, 2);
+               s = v1 * v1 + v2 * v2;
+       } while (s >= 1.0);
 
-               if (s >= 1.0)
-                       continue;
-
-               if (s == 0)
-               {
-                       *x1 = 0;
-                       *x2 = 0;
-               }
-               else
-               {
-                       *x1 = v1 * sqrt((-2.0 * log(s)) / s);
-                       *x2 = v2 * sqrt((-2.0 * log(s)) / s);
-               }
-
-               return;
+       if (s == 0)
+       {
+               *x1 = 0;
+               *x2 = 0;
+       }
+       else
+       {
+               s = sqrt((-2.0 * log(s)) / s);
+               *x1 = v1 * s;
+               *x2 = v2 * s;
        }
 }