/******************************************************************************
* FILE: loop08.c
* DESCRIPTION:
*   Demonstrates loop defactorization
******************************************************************************/

#include <stdio.h>
#include <sys/time.h>
#include <time.h>
#define ARRAY_SIZE	5000
#define	SEED		1995

double a[ARRAY_SIZE], b[ARRAY_SIZE], c[ARRAY_SIZE], d[ARRAY_SIZE];
double aa[ARRAY_SIZE], bb[ARRAY_SIZE], cc[ARRAY_SIZE], dd[ARRAY_SIZE];
struct timeval start_time, end_time;

main()
{
   int i, j, tmp;
   initialize_data();

/*****************************************************************************/
/*				Factorized Loop				     */
/*****************************************************************************/
   gettimeofday(&start_time, (struct timeval*)0);

   for(i=0;i<ARRAY_SIZE;i++)
   {
      a[i] = 0.0;
      for(j=0;j<ARRAY_SIZE;j++)
         a[i] = a[i] + b[j] * d[j] * c[i];
   }

   gettimeofday(&end_time, (struct timeval*)0);  /* after time */
   printf("Execution time for the untuned loop:\n");
   print_execution_times();

/*****************************************************************************/
/*				Defactorized Loop			     */
/*****************************************************************************/
   gettimeofday(&start_time, (struct timeval*)0);

   for(i=0;i<ARRAY_SIZE;i++)
   {
      aa[i] = 0.0;
      for(j=0;j<ARRAY_SIZE;j++)
         aa[i] = aa[i] + bb[j] * dd[j];
      aa[i] = aa[i] * cc[i];
   }

   gettimeofday(&end_time, (struct timeval*)0);  /* after time */
   printf("Execution time for the tuned loop:\n");
   print_execution_times();
   finalize_data();
}

initialize_data()
{
   int i, k;
   srandom(SEED);
   for(i=0;i<ARRAY_SIZE;i++)
   {
      aa[i] = a[i] = (float) (random() % 100000);
      bb[i] = b[i] = (float) (random() % 100000);
      cc[i] = c[i] = (float) (random() % 100000);
      dd[i] = d[i] = (float) (random() % 100000);
   }
}

finalize_data()
{
   int i;
   FILE *fp, *fopen();

   fp = fopen("/dev/null", "w");
   i = random() % ARRAY_SIZE;
   fprintf(fp, "%f\n", a[i]);
   fprintf(fp, "%f\n", aa[i]);
   fclose(fp);
}

print_execution_times()
{
   int total_usecs;
   float total_time;
   total_usecs = (end_time.tv_sec-start_time.tv_sec) * 1000000 +
         (end_time.tv_usec-start_time.tv_usec);
   printf("Total time was %.2f mSec\n", ((float) total_usecs) / 1000.0);
   total_time = ((float) total_usecs) / 1000000.0;
}