benchtests: Improve reliability of memcmp benchmarks

No bug. Remove reallocation of bufs between implementation tests. Move
initialization outside of foreach implementation test loop. Increase
iteration count.

Generally before this commit was seeing a great deal of variability
between runs. The goal of this commit is to make the results more
reliable.

Benchtests build and bench-memcmp succeeding.

Signed-off-by: Noah Goldstein <goldstein.w.n@gmail.com>

diff --git a/benchtests/bench-memcmp.c b/benchtests/bench-memcmp.c
index 744c7ec..0d6a93b 100644 (file)
--- a/benchtests/bench-memcmp.c
+++ b/benchtests/bench-memcmp.c
@@ -63,7 +63,7 @@ static void
 do_one_test (json_ctx_t *json_ctx, impl_t *impl, const CHAR *s1,
             const CHAR *s2, size_t len, int exp_result)
 {
-  size_t i, iters = INNER_LOOP_ITERS8;
+  size_t i, iters = INNER_LOOP_ITERS_LARGE;
   timing_t start, stop, cur;
 
   TIMING_NOW (start);
@@ -103,20 +103,19 @@ do_test (json_ctx_t *json_ctx, size_t align1, size_t align2, size_t len,
   json_attr_uint (json_ctx, "result", (double) exp_result);
   json_array_begin (json_ctx, "timings");
 
-  FOR_EACH_IMPL (impl, 0)
-    {
-      s1 = (CHAR *) (buf1 + align1);
-      s2 = (CHAR *) (buf2 + align2);
+  s1 = (CHAR *)(buf1 + align1);
+  s2 = (CHAR *)(buf2 + align2);
 
-      for (i = 0; i < len; i++)
-       s1[i] = s2[i] = 1 + (23 << ((CHARBYTES - 1) * 8)) * i % MAX_CHAR;
+  for (i = 0; i < len; i++)
+    s1[i] = s2[i] = 1 + (23 << ((CHARBYTES - 1) * 8)) * i % MAX_CHAR;
 
-      s1[len] = align1;
-      s2[len] = align2;
-      s2[len - 1] -= exp_result;
+  s1[len] = align1;
+  s2[len] = align2;
+  s2[len - 1] -= exp_result;
 
+  FOR_EACH_IMPL (impl, 0)
+    {
       do_one_test (json_ctx, impl, s1, s2, len, exp_result);
-      alloc_bufs ();
     }
 
   json_array_end (json_ctx);