/*

 * dotprod.c

 *     Εσωτερικό γινόμενο δύο διανυσμάτων χρησιμοποιώντας MPI

*  Created on: 31 Οκτ 2011

 *      Author: Kostas Diamantaras

 */

#include "mpi.h"

#include <stdio.h>

#include <string.h>

#include <math.h>

int main(int argc, char **argv) {

int procs, rank;

double x[1000], y[1000];

double local_x[1000], local_y[1000];

int i, n;

int partSize;

FILE *fid;

char *sFileName, defaultName[] = "dotprod.dat";

double local_prod, prod, trueProd;

MPI_Init(&argc, &argv);

MPI_Comm_size(MPI_COMM_WORLD, &procs);

MPI_Comm_rank(MPI_COMM_WORLD, &rank);

if (rank==0) {

if (argc==2) {

/* The filename is the first argument of the program */

                     sFileName = argv[1];

              } else {

/* Default file name */

                     sFileName = defaultName;

              }

printf("Opening file: %s\n", sFileName);

              fid = fopen(sFileName,"r");

/* Read vector dimensions */

fscanf(fid, "%d", &n);

printf("Vector dimensions: %d\n", n);

/* Read vector x */

for (i=0; i<n; i++) {

fscanf(fid, "%lf", &(x[i]));

              }

/* Read vector y */

for (i=0; i<n; i++) {

fscanf(fid, "%lf", &(y[i]));

              }

/* Read true inner product */

fscanf(fid, "%lf", &trueProd);

fclose(fid);

       }      /* end if rank == 0 */

/* Broadcast n */

MPI_Bcast(&n, 1, MPI_INT, 0, MPI_COMM_WORLD);

/* Partition x[] and y[] into "procs"-many parts

        * of size ceil(n / procs) each.

        */

       partSize = ceil(n / procs);

MPI_Scatter(x, partSize, MPI_DOUBLE, local_x, partSize, MPI_DOUBLE, 0, MPI_COMM_WORLD);

MPI_Scatter(y, partSize, MPI_DOUBLE, local_y, partSize, MPI_DOUBLE, 0, MPI_COMM_WORLD);

/* Partial Inner Product */

       local_prod = 0;

for (i=0; i<partSize; i++) {

              local_prod += local_x[i] * local_y[i];

       }

MPI_Reduce(&local_prod, &prod, 1, MPI_DOUBLE, MPI_SUM, 0, MPI_COMM_WORLD);

if (rank==0) {

printf("Computed Inner Product\t=\t%.6f\n", prod);

printf("True Inner Product\t=\t%.6f\n", trueProd);

fflush(stdout);

       }

MPI_Finalize();

return(0);

}