source: CIVL/examples/mpi-omp/mpi-omp-mat-vect-mult-blkstp.c

#ifdef _CIVL
#include <civlc.cvh>
#endif
/*********************************************************************
              C-DAC Tech Workshop : HeGaPa-2012
                     July 16-20,2012

  Example 4           : Mpi-Omp_MatVect_Mult_blkstp.c
  
  Objective           : Write an MPI-OpenMP Program to perform Matrix-Vector
                        Multiplication
  
  Input               : Process 0 reads files (mdata.inp) for Matrix and
                        (vdata.inp) for Vector
  
  Output              : Process 0 prints the result of Matrix_Vector
                        Multiplication

  Created           : MAY-2012    
**********************************************************************/



#include <stdio.h>
#include "mpi.h"
#include <stdlib.h>
#include<omp.h>
#include<math.h>

/* Main Program */

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

  int             Numprocs, MyRank, iam;
  int             NoofCols, NoofRows, VectorSize, ScatterSize;
  int             index, irow, icol, iproc;
  int             Root = 0, ValidOutput = 1;
  float         **Matrix, *Buffer, *Mybuffer, *Vector, *MyFinalVector,
    *FinalVector;
  float          *CheckResultVector;
  FILE           *fp;
  int             MatrixFileStatus = 1, VectorFileStatus = 1;


  /* ........MPI Initialisation ....... */

  MPI_Init(&argc, &argv);
  MPI_Comm_rank(MPI_COMM_WORLD, &MyRank);
  MPI_Comm_size(MPI_COMM_WORLD, &Numprocs);

  if (MyRank == 0) {
    /* .......Read The Input File ...... */
    if ((fp = fopen("./data/mdata.inp", "r")) == NULL) {
      MatrixFileStatus = 0;
    }
    if (MatrixFileStatus != 0) {
      fscanf(fp, "%d %d\n", &NoofRows, &NoofCols);

      /*
       * ...Allocate Memory And Read Matrix From File
       * .......
       */
      Matrix = (float **) malloc(NoofRows * sizeof(float *));
      for (irow = 0; irow < NoofRows; irow++) {
        Matrix[irow] = (float *) malloc(NoofCols * sizeof(float));
        for (icol = 0; icol < NoofCols; icol++) {
          fscanf(fp, "%f", &Matrix[irow][icol]);
        }
      }
      fclose(fp);

      /* .......Convert 2-D Matrix Into 1-D Array ..... */
      Buffer = (float *) malloc(NoofRows * NoofCols * sizeof(float));

      index = 0;
      for (irow = 0; irow < NoofRows; irow++) {
        for (icol = 0; icol < NoofCols; icol++) {
          Buffer[index] = Matrix[irow][icol];
          index++;
        }
      }
    }
    /* Read Vector From Input File */
    if ((fp = fopen("./data/vdata.inp", "r")) == NULL) {
      VectorFileStatus = 0;
    }
    if (VectorFileStatus != 0) {
      fscanf(fp, "%d\n", &VectorSize);

      Vector = (float *) malloc(VectorSize * sizeof(float));
      for (index = 0; index < VectorSize; index++)
        fscanf(fp, "%f", &Vector[index]);

    }
  }/* End  Of If Myrank = 0 */
  MPI_Barrier(MPI_COMM_WORLD);

  MPI_Bcast(&MatrixFileStatus, 1, MPI_INT, Root, MPI_COMM_WORLD);
  if (MatrixFileStatus == 0) {
    if (MyRank == Root)
      printf("Can't Open Input File For Matrix ..... \n");
    MPI_Finalize();
    exit(-1);
  }
  MPI_Bcast(&VectorFileStatus, 1, MPI_INT, Root, MPI_COMM_WORLD);
  if (VectorFileStatus == 0) {
    if (MyRank == Root)
      printf("Can't Open Input File For Vector ..... \n");
    MPI_Finalize();
    exit(-1);
  }
  MPI_Bcast(&NoofRows, 1, MPI_INT, Root, MPI_COMM_WORLD);

  #ifdef _CIVL
  $assume(NoofRows >= Numprocs);
  #endif
  if (NoofRows < Numprocs) {
    if (MyRank == 0)
      printf("No Of Rows Should Be More Than No Of Processors ... \n");
    MPI_Finalize();
    exit(0);
  }
    #ifdef _CIVL
  $assume(NoofRows % Numprocs == 0);
  #endif
  if (NoofRows % Numprocs != 0) {
    if (MyRank == 0)
      printf("Matrix Cannot Be Striped Evenly ..... \n");
    MPI_Finalize();
    exit(0);
  }
  MPI_Bcast(&NoofCols, 1, MPI_INT, Root, MPI_COMM_WORLD);
  MPI_Bcast(&VectorSize, 1, MPI_INT, Root, MPI_COMM_WORLD);

  if (VectorSize != NoofCols) {
    if (MyRank == 0) {
      printf("Invalid Input Data..... \n");
      printf("NoofCols Should Be Equal To VectorSize\n");
    }
    MPI_Finalize();
    exit(0);
  }
  if (MyRank != 0)
    Vector = (float *) malloc(VectorSize * sizeof(float));
  MPI_Bcast(Vector, VectorSize, MPI_FLOAT, Root, MPI_COMM_WORLD);

  ScatterSize = NoofRows / Numprocs;
  Mybuffer = (float *) malloc(ScatterSize * NoofCols * sizeof(float));
  MPI_Scatter(Buffer, ScatterSize * NoofCols, MPI_FLOAT, Mybuffer,
              ScatterSize * NoofCols, MPI_FLOAT, 0, MPI_COMM_WORLD);

  MyFinalVector = (float *) malloc(ScatterSize * sizeof(float));

  for (irow = 0; irow < ScatterSize; irow++)
    MyFinalVector[irow] = 0;

  printf("\n");


  /* OpenMP Parallel Directive */

  /*
#pragma omp parallel  private(iam)
{

OpenMP Parallel For Directive */

  omp_set_num_threads(4);
#pragma omp parallel for private(index,icol,iam)
 for (irow = 0; irow < ScatterSize; irow++) {
   printf("The Threadid is %d with  each processor Rank %d\n", omp_get_thread_num(), MyRank);
   MyFinalVector[irow] = 0;
   index = irow * NoofCols;
   for (icol = 0; icol < NoofCols; icol++)
     MyFinalVector[irow] += (Mybuffer[index++] * Vector[icol]);
 }

 MPI_Barrier(MPI_COMM_WORLD);

 if (MyRank == 0)
   FinalVector = (float *) malloc(NoofRows * sizeof(float));


 MPI_Gather(MyFinalVector, ScatterSize, MPI_FLOAT, FinalVector,
            ScatterSize, MPI_FLOAT, Root, MPI_COMM_WORLD);

 if (MyRank == 0) {
   printf("\n");
   printf(" --------------------------------------------------- \n");
   /* printf("Results of Gathering Data  %d: \n", MyRank); */
   printf("\n");

   for (index = 0; index < NoofRows; index++)
     printf(" FinalVector[%d] = %f \n", index, FinalVector[index]);
   printf(" --------------------------------------------------- \n");
 }
 if (MyRank == 0) {
   CheckResultVector = (float *) malloc(NoofRows * sizeof(float));
   for (irow = 0; irow < NoofRows; irow++) {
     CheckResultVector[irow] = 0;
     for (icol = 0; icol < NoofCols; icol++) {
       CheckResultVector[irow] += (Matrix[irow][icol] * Vector[icol]);
     }
     if (fabs((double) (FinalVector[irow] - CheckResultVector[irow])) >
         1.0E-10) {
       printf("Error %d\n", irow);
       ValidOutput = 0;
     }
   }
   if (ValidOutput)
     printf("\n-------Correct Result------\n");
   /* Freeing Allocated Memory */
   free(Matrix);
   free(Vector);
   free(Buffer);
   free(FinalVector);
   free(CheckResultVector);
 }

 /* Freeing Allocated Memory */
 free(Mybuffer);
 free(MyFinalVector);

 /* MPI-Termination */

 MPI_Finalize();

}