dotprod_serial.c

/*****************************************************************************
* FILE: omp_dotprod_serial.c
* DESCRIPTION:
*   This simple program is the serial version of a dot product and the
*   first of four codes used to show the progression from a serial program to a 
*   hybrid MPI/OpenMP program.  The relevant codes are:
*      - omp_dotprod_serial.c  - Serial version
*      - omp_dotprod_openmp.c  - OpenMP only version
*      - omp_dotprod_mpi.c     - MPI only version
*      - omp_dotprod_hybrid.c  - Hybrid MPI and OpenMP version
* SOURCE: Blaise Barney
* LAST REVISED:  06/02/17 Blaise Barney
******************************************************************************/

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

#include "timing.h"

/* Define length of dot product vectors */
#define VECLEN 1000000000

int main (int argc, char* argv[])
{
int i,len=VECLEN;
double *a, *b;
double sum;
timing_t tstart, tend;

printf("Starting omp_dotprod_serial\n");

/* Assign storage for dot product vectors */
a = (double*) malloc (len*sizeof(double));
b = (double*) malloc (len*sizeof(double));
 
/* Initialize dot product vectors */
for (i=0; i<len; i++) {
  a[i]=1.0;
  b[i]=a[i];
  }

/* Perform the dot product */
sum = 0.0;
get_time(&tstart);
/*
for (i=0; i<len; i++) 
  {
    sum += (a[i] * b[i]);
  }*/

/* Perform the dot product with 2x loop unrolling 
for (i=0; i<len; i+=2) 
  {
    sum += (a[i] * b[i]);
    sum += (a[i+1] * b[i+1]);
  }*/

 /* Perform the dot product with 4x loop unrolling*/
for (i=0; i<len; i+=4) 
  {
    sum += (a[i] * b[i]);
    sum += (a[i+1] * b[i+1]);
    sum += (a[i+2] * b[i+2]);
    sum += (a[i+3] * b[i+3]);
  }
get_time(&tend);

printf ("Serial version: sum  =  %f \n"
        "Elapsed time: %g s\n", sum, timespec_diff(tstart,tend));

free (a);
free (b);
}