testing/fork-join.c

   1 #include <mach/mach.h>
   2 #include <mach/mach_time.h>
   3 #include <dispatch/dispatch.h>
   4 #include <dispatch/private.h>
   5 #include <stdio.h>
   6 #include <stdlib.h>
   7 #include <assert.h>
   8
   9 int
  10 main(void)
  11 {
  12         long double nano_per_lap;
  13         size_t i, cnt = 1000000;
  14         dispatch_future_t *df;
  15         uint64_t s, e;
  16
  17         df = malloc(cnt * sizeof(df));
  18         assert(df);
  19
  20         s = mach_absolute_time();
  21
  22         for (i = 0; i < cnt; i++) {
  23                 df[i] = dispatch_fork(dispatch_get_concurrent_queue(0), ^{
  24                 });
  25                 assert(df[i]);
  26         }
  27
  28         for (i = 0; i < cnt; i++) {
  29                 dispatch_join(df[i]);
  30         }
  31
  32         e = mach_absolute_time();
  33
  34         nano_per_lap = (e - s);
  35         nano_per_lap /= cnt;
  36
  37         printf("%Lf nanoseconds per lap\n", nano_per_lap);
  38
  39         return 0;
  40 }