benchtests/bench-skeleton.c

   1 /* Skeleton for benchmark programs.
   2    Copyright (C) 2013-2014 Free Software Foundation, Inc.
   3    This file is part of the GNU C Library.
   4
   5    The GNU C Library is free software; you can redistribute it and/or
   6    modify it under the terms of the GNU Lesser General Public
   7    License as published by the Free Software Foundation; either
   8    version 2.1 of the License, or (at your option) any later version.
   9
  10    The GNU C Library is distributed in the hope that it will be useful,
  11    but WITHOUT ANY WARRANTY; without even the implied warranty of
  12    MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  13    Lesser General Public License for more details.
  14
  15    You should have received a copy of the GNU Lesser General Public
  16    License along with the GNU C Library; if not, see
  17    <http://www.gnu.org/licenses/>.  */
  18
  19 #include <string.h>
  20 #include <stdint.h>
  21 #include <stdbool.h>
  22 #include <stdio.h>
  23 #include <time.h>
  24 #include <inttypes.h>
  25 #include "bench-timing.h"
  26 #include "json-lib.h"
  27
  28 volatile unsigned int dontoptimize = 0;
  29
  30 void
  31 startup (void)
  32 {
  33   /* This loop should cause CPU to switch to maximal freqency.
  34      This makes subsequent measurement more accurate.  We need a side effect
  35      to prevent the loop being deleted by compiler.
  36      This should be enough to cause CPU to speed up and it is simpler than
  37      running loop for constant time. This is used when user does not have root
  38      access to set a constant freqency.  */
  39   for (int k = 0; k < 10000000; k++)
  40     dontoptimize += 23 * dontoptimize + 2;
  41 }
  42
  43 #define TIMESPEC_AFTER(a, b) \
  44   (((a).tv_sec == (b).tv_sec) ?                                               \
  45      ((a).tv_nsec > (b).tv_nsec) :                                            \
  46         ((a).tv_sec > (b).tv_sec))
  47 int
  48 main (int argc, char **argv)
  49 {
  50   unsigned long i, k;
  51   struct timespec runtime;
  52   timing_t start, end;
  53   bool detailed = false;
  54   json_ctx_t json_ctx;
  55
  56   if (argc == 2 && !strcmp (argv[1], "-d"))
  57     detailed = true;
  58
  59   startup();
  60
  61   memset (&runtime, 0, sizeof (runtime));
  62
  63   unsigned long iters, res;
  64
  65   TIMING_INIT (res);
  66
  67   iters = 1000 * res;
  68
  69   json_init (&json_ctx, 2, stdout);
  70
  71   /* Begin function.  */
  72   json_attr_object_begin (&json_ctx, FUNCNAME);
  73
  74   for (int v = 0; v < NUM_VARIANTS; v++)
  75     {
  76       /* Run for approximately DURATION seconds.  */
  77       clock_gettime (CLOCK_MONOTONIC_RAW, &runtime);
  78       runtime.tv_sec += DURATION;
  79
  80       double d_total_i = 0;
  81       timing_t total = 0, max = 0, min = 0x7fffffffffffffff;
  82       int64_t c = 0;
  83       while (1)
  84         {
  85           for (i = 0; i < NUM_SAMPLES (v); i++)
  86             {
  87               uint64_t cur;
  88               TIMING_NOW (start);
  89               for (k = 0; k < iters; k++)
  90                 BENCH_FUNC (v, i);
  91               TIMING_NOW (end);
  92
  93               TIMING_DIFF (cur, start, end);
  94
  95               if (cur > max)
  96                 max = cur;
  97
  98               if (cur < min)
  99                 min = cur;
 100
 101               TIMING_ACCUM (total, cur);
 102               /* Accumulate timings for the value.  In the end we will divide
 103                  by the total iterations.  */
 104               RESULT_ACCUM (cur, v, i, c * iters, (c + 1) * iters);
 105
 106               d_total_i += iters;
 107             }
 108           c++;
 109           struct timespec curtime;
 110
 111           memset (&curtime, 0, sizeof (curtime));
 112           clock_gettime (CLOCK_MONOTONIC_RAW, &curtime);
 113           if (TIMESPEC_AFTER (curtime, runtime))
 114             goto done;
 115         }
 116
 117       double d_total_s;
 118       double d_iters;
 119
 120     done:
 121       d_total_s = total;
 122       d_iters = iters;
 123
 124       /* Begin variant.  */
 125       json_attr_object_begin (&json_ctx, VARIANT (v));
 126
 127       json_attr_double (&json_ctx, "duration", d_total_s);
 128       json_attr_double (&json_ctx, "iterations", d_total_i);
 129       json_attr_double (&json_ctx, "max", max / d_iters);
 130       json_attr_double (&json_ctx, "min", min / d_iters);
 131       json_attr_double (&json_ctx, "mean", d_total_s / d_total_i);
 132
 133       if (detailed)
 134         {
 135           json_array_begin (&json_ctx, "timings");
 136
 137           for (int i = 0; i < NUM_SAMPLES (v); i++)
 138             json_element_double (&json_ctx, RESULT (v, i));
 139
 140           json_array_end (&json_ctx);
 141         }
 142
 143       /* End variant.  */
 144       json_attr_object_end (&json_ctx);
 145     }
 146
 147   /* End function.  */
 148   json_attr_object_end (&json_ctx);
 149
 150   return 0;
 151 }