Various elementary CPU operations benchmark

cpu-perf-test.cxx

# gcc -O3 -o cpu-perf-test -lrt cpu-perf-test.cxx && (for x in {1..7}; do sleep 0.3s; ./cpu-perf-test; done) && rm cpu-perf-test
#include <time.h>
#include <stdio.h>
#include <stdlib.h>


//const char *op_tag = "id "; long op(long x) { return x; }
const char *op_tag = "*2 "; long op(long x) { return x * 2; }
//const char *op_tag = "<<1"; long op(long x) { return x << 1; }
//const char *op_tag = "*27"; long op(long x) { return x * 27; }
//const char *op_tag = "*31"; long op(long x) { return x * 31; }


long f1(long *a, long size) {
  long sum = 0;
  for (long i = 0; i < size; i++) {
    sum += op(a[i]);
  }
  return sum;
}


long long diff(timespec *t1, timespec *t2) {
  return ((t2->tv_sec - t1->tv_sec) * 1e9) + (t2->tv_nsec - t1->tv_nsec);
}


int main() {
  timespec t1, t2;

  long size = 1000000;
  long *a = (long*)malloc(sizeof(long) * size);
  // fill with interesting values
  a[0] = 7;
  for (long i = 1; i < size; i++) {
    a[i] = a[i - 1] * 137 + 5;
  }

  if (clock_gettime(CLOCK_MONOTONIC_RAW, &t1)) {
    perror("clock_gettime t1");
    return 1;
  }

  long sum = f1(a, size) + f1(a, size);

  if (clock_gettime(CLOCK_MONOTONIC_RAW, &t2)) {
    perror("clock_gettime t2");
    return 1;
  }
  long long time = diff(&t1, &t2);
  if (time == 0) {
    fprintf(stderr, "measured time difference = 0\n");
    return 1;
  }
  printf("op: %s result: %Ld size: %Ld time: %Ld speed: %Ld\n", op_tag, sum, size, time, size * 1000000 / time);

  return 0;
}