/* Uses sequential accesses to determine cache size
 * By P. Koopman  for CMU 18-742   Spring 1998
 * Also used for CMU 18-548 Fall 1998
 *
 * Note: this program is not *guaranteed* to work on
 *   all platforms -- use common sense to make sure the
 *   results you are getting are appropriate
 * Also, major changes will have to be made to conform
 *   to the requirements of the homework solution.
 */

#include <sys/times.h>
#include <sys/types.h>
#define HZ 60
#include <stdio.h>
#include <stdlib.h>

#define K  * 1024
#define M  * 1024 * 1024

/* Tune TUNE for machine speed;  larger number runs slower */
#define TUNE  1 M

#define MAXSIZE (10 K)

/* it's easy to cash a check, but hard to check a cache */
int touch_array(int *array, int num_ints, int iterations)
{ int i;
  int sum=0;
  int *p, *limit;

  limit = &(array[num_ints-1]);

  for (i = 0; i < iterations; i++)
  {
    /* touch elements; pointer match results in faster code */
    for (p = array; p != limit; p++)
    { sum += *p; }
  }
  return(sum);
}


void main(void)
{ int *a;           /* data array */
  int size, j, iter;
  int num_ints;     /* number of ints in the array */
  int result;
  double x, elapsed, rate;

  struct tms time_info;
  long Begin_Time, End_Time;

  printf("\n\nTesting tuning value of %d\n", TUNE);
  printf("Array size, Iterations, seconds, bytes/sec\n");

  for (size = 1 K; size < MAXSIZE; size += 1 K )
  { a = (int *) malloc(size);
    num_ints = size / sizeof(int);

    /* initialize array to a constant value */
    for (j = 0; j < num_ints; j++)  { a[j] = 1; }   

    /* scale iterations with array size, so run time is about constant */
    x = size;   
    x = (TUNE) / x;
    iter = x * 100;

    /* pre-load cache to avoid compulsory misses */
    result = touch_array(a, num_ints, 1);

    /* start timer */
    printf("%9d, %10d, ", size, iter);
    times (&time_info);
    Begin_Time = (long) time_info.tms_utime;

    /* touch the array repeatedly */
    result += touch_array(a, num_ints, iter);

    /* stop timer */
    times (&time_info);
    End_Time = (long) time_info.tms_utime;
    elapsed = ((double) (End_Time - Begin_Time) ) / HZ ;

    rate = size;  rate = rate * iter / elapsed;

    /* make print conditional on non-zero result to foil
     *  global optimizers  (result will always be non-zero)
     */
    if (result)
      printf("%.3f, %.f\n", elapsed, rate);

    free(a);
    }  /* next bigger array size */
}