small memory access benchmark

mem_bm.c

#include <stdio.h>
#include <stdlib.h>

#define TEST_SIZE 10000000

long arr[TEST_SIZE];

void usage (char *name)
{
  printf("USAGE: %s [forward|reverse|both]", name);
  exit (1);
}

int main (int argc, char *argv[])
{
  int i,j;
  char mode;
  if (argc != 2)
    usage (argv[0]);
  mode = argv[1][0];
  if (mode != 'f' && mode != 'r' && mode != 'b')
    usage (argv[0]);
  for (j=0; j<100; j++) {
    switch (mode) {
      case 'f':
        for (i=1; i<TEST_SIZE; i++)
          arr[i-1] += arr[i];
        break;
      case 'r':
        for (i=TEST_SIZE-1; i>=1; i--)
          arr[i-1] += arr[i];
        break;
      case 'b':
        for (i=TEST_SIZE-1; i>=1; i--)
          arr[TEST_SIZE-i] += arr[i];
        break;
    }
  }
}