/******************************************************************************
* FILE: arit01.c
* DESCRIPTION:
*   Demonstrates Horner's Rule of Polynomial Evaluation 
******************************************************************************/

#include <stdio.h>
#include <sys/time.h>
#include <time.h>
#define ARRAY_SIZE	10000
#define	SEED		1995

float a[ARRAY_SIZE], aa[ARRAY_SIZE];
float b[ARRAY_SIZE], bb[ARRAY_SIZE];
float c[ARRAY_SIZE], cc[ARRAY_SIZE];
float d[ARRAY_SIZE], dd[ARRAY_SIZE];
float e[ARRAY_SIZE], ee[ARRAY_SIZE];
float f[ARRAY_SIZE], ff[ARRAY_SIZE];
float x, xx;
struct timeval start_time, end_time;

main()
{
   int i;
   initialize_data();

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

   for(i=0;i<ARRAY_SIZE;i++)
   {
      x = a[i] * pow(x, 5) + 
          b[i] * pow(x, 4) +
          c[i] * pow(x, 3) +
          d[i] * pow(x, 2) +
          e[i] * x +
          f[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++)
   {
      xx = ((((aa[i] * xx + bb[i]) * xx + cc[i]) * xx + dd[i]) *
             xx + ee[i]) * xx + ff[i];
   }

   gettimeofday(&end_time, (struct timeval*)0);  /* after time */
   printf("Execution time for the tuned loops:\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);
      ee[i] = e[i] = (float) (random() % 100000);
      ff[i] = f[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;
}