/******************************************************************************
* FILE: loop06.c
* DESCRIPTION:
*   Demonstrates invarient IF code optimization
******************************************************************************/

#include <stdio.h>
#include <sys/time.h>
#include <time.h>
#define ARRAY_SIZE	100
#define	SEED		1995

float a[ARRAY_SIZE], b[ARRAY_SIZE];
float aa[ARRAY_SIZE], bb[ARRAY_SIZE];
float x, xx;
struct timeval start_time, end_time;

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

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

   for(i=0;i<ARRAY_SIZE;i++)
   {
      for(j=0;j<ARRAY_SIZE;j++)
      {
         srandom(SEED);
         if (a[random() % ARRAY_SIZE] >= 100.0)
            b[i] = a[i] - 3.7;
         x = x + a[j] + b[i];
      }
   }

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

   for(i=0;i<ARRAY_SIZE;i++)
   {
      srandom(SEED);
      if (aa[random() % ARRAY_SIZE] >= 100.0)
         bb[i] = aa[i] - 3.7;

      for(j=0;j<ARRAY_SIZE;j++)
         xx = xx + aa[j] + bb[i];
   }

   gettimeofday(&end_time, (struct timeval*)0);  /* after time */
   printf("Execution time for the tuned loops:\n");
   print_execution_times();
   printf("Computed result from each loop %f and %f\n", x, xx);
   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);
   }
   xx = x = 0.0;
}

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

   fp = fopen("/dev/null", "w");
   fprintf(fp, "%f\n", x);
   fprintf(fp, "%f\n", xx);
   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;
}