[PATCH] randomize benchtests

[OndÅej BÃlka <neleai at seznam dot cz>]

Hi,

I added ordering randomization in benchtest to capture more realistic
data. This takes into account branch misprediction which easily is 20%
of running time.

Indepentently I print results in saner metrics namely average,
minimum and maximum time.

Do you know more portable way to get CPU frequency than reading /dev/cpuinfo?
I need that to display data at cycles which are more natural unit than
nanoseconds.

	* benchtests/bench-skeleton.c (main): Randomize ordering.

---
 benchtests/bench-skeleton.c |   44 +++++++++++++++++++-----------------------
 1 files changed, 20 insertions(+), 24 deletions(-)

diff --git a/benchtests/bench-skeleton.c b/benchtests/bench-skeleton.c
index 13f986d..3061633 100644
--- a/benchtests/bench-skeleton.c
+++ b/benchtests/bench-skeleton.c
@@ -18,6 +18,7 @@
 
 #include <string.h>
 #include <stdint.h>
+#include <stdlib.h>
 #include <stdio.h>
 #include <time.h>
 #include <inttypes.h>
@@ -28,7 +29,7 @@ main (int argc, char **argv)
   unsigned long i, j, k;
   uint64_t total = 0, max = 0, min = 0x7fffffffffffffff;
   struct timespec start, end;
-
+  int seed = 42;
   memset (&start, 0, sizeof (start));
   memset (&end, 0, sizeof (end));
 
@@ -41,35 +42,30 @@ main (int argc, char **argv)
   unsigned long iters = 1000 * start.tv_nsec;
   unsigned long total_iters = ITER / iters;
 
-  for (i = 0; i < NUM_SAMPLES; i++)
+  for (j = 0; j < NUM_SAMPLES * total_iters; j ++)
     {
-      for (j = 0; j < total_iters; j ++)
-	{
-	  clock_gettime (CLOCK_PROCESS_CPUTIME_ID, &start);
-	  for (k = 0; k < iters; k++)
-	    BENCH_FUNC(i);
-	  clock_gettime (CLOCK_PROCESS_CPUTIME_ID, &end);
-
-	  uint64_t cur = (end.tv_nsec - start.tv_nsec
-			 + ((end.tv_sec - start.tv_sec)
-			    * (uint64_t) 1000000000));
-
-	  if (cur > max)
-	    max = cur;
+      clock_gettime (CLOCK_PROCESS_CPUTIME_ID, &start);
+      for (k = 0; k < iters; k++)
+        {
+	  i = rand_r (&seed)%NUM_SAMPLES;	
+	  BENCH_FUNC(i);
+        }
+      clock_gettime (CLOCK_PROCESS_CPUTIME_ID, &end);
 
-	  if (cur < min)
-	    min = cur;
+      uint64_t cur = (end.tv_nsec - start.tv_nsec
+		     + ((end.tv_sec - start.tv_sec)
+		       * (uint64_t) 1000000000));
 
-	  total += cur;
-	}
+      if (cur > max)
+        max = cur;
+      if (cur < min)
+        min = cur;
+      total += cur;
     }
 
-  double d_total_s = total * 1e-9;
-  double d_iters = iters;
   double d_total_i = (double)ITER * NUM_SAMPLES;
-  printf (FUNCNAME ": ITERS:%g: TOTAL:%gs, MAX:%gns, MIN:%gns, %g iter/s\n",
-	  d_total_i, d_total_s, max / d_iters, min / d_iters,
-	  d_total_i / d_total_s);
+  printf (FUNCNAME ": AVERAGE:%gns\tMIN:%gns,\tMAX:%gns\n",
+	        d_total / d_total_i, min / iters, max / iters);
 
   return 0;
 }
-- 
1.7.4.4