examples-mpi2/examples/mm.c

/******************************************************************************
 * * MPI Matrix Multiply - C Version
 * * FILE: mpi_mm.c
 * * OTHER FILES: make.mpi_mm.c
 * * DESCRIPTION:  
 * *   In this code, the master task distributes a matrix multiply
 * *   operation to numtasks-1 worker tasks.
 * *   NOTE1:  C and Fortran versions of this code differ because of the way
 * *   arrays are stored/passed.  C arrays are row-major order but Fortran
 * *   arrays are column-major order.
 * * AUTHOR: Ros Leibensperger / Blaise Barney
 * * CONVERTED TO MPI: George L. Gusciora (1/25/95)
 * ******************************************************************************/
#include "mpi.h"
#include <stdio.h>
#define NRA 62 				/* number of rows in matrix A */
#define NCA 15				/* number of columns in matrix A */
#define NCB 7   			/* number of columns in matrix B */
#define MASTER 0			/* taskid of first task */
#define FROM_MASTER 1			/* setting a message type */
#define FROM_WORKER 2			/* setting a message type */

int main(argc,argv)
int argc;
char *argv[];
{
int	numtasks,	/* number of tasks in partition */
	taskid,		/* a task identifier */
	numworkers,	/* number of worker tasks */
	source,		/* task id of message source */
	dest,		/* task id of message destination */
	nbytes,		/* number of bytes in message */
	mtype,		/* message type */
	rows,          	/* rows of matrix A sent to each worker */
	averow, extra, offset,
			/* used to determine rows sent to each worker */
	i, j, k, rc; 	/* misc */
double	a[NRA][NCA],	/* matrix A to be multiplied */
	b[NCA][NCB],   	/* matrix B to be multiplied */
	c[NRA][NCB]; 	/* result matrix C */
MPI_Status status;

   rc = MPI_Init(&argc,&argv);
   rc|= MPI_Comm_size(MPI_COMM_WORLD,&numtasks);
   rc|= MPI_Comm_rank(MPI_COMM_WORLD,&taskid);
   if (rc != 0)
      printf ("error initializing MPI and obtaining task ID information\n");
   else
      printf ("mpi_pi_mm MPI task ID = %d\n", taskid);
   numworkers = numtasks-1;
/**************************** master task ************************************/
   if (taskid == MASTER)
   {
      printf("Number of worker tasks = %d\n",numworkers);
      for (i=0; i<NRA; i++)
         for (j=0; j<NCA; j++)
            a[i][j]= i+j;
      for (i=0; i<NCA; i++)
         for (j=0; j<NCB; j++)
            b[i][j]= i*j;

      /* send matrix data to the worker tasks */
      averow = NRA/numworkers;
      extra = NRA%numworkers;
      offset = 0;
      mtype = FROM_MASTER;
      for (dest=1; dest<=numworkers; dest++)
      {
         rows = (dest <= extra) ? averow+1 : averow;   	
         printf("   sending %d rows to task %d\n",rows,dest);
         MPI_Send(&offset, 1, MPI_INT, dest, mtype, MPI_COMM_WORLD);
         MPI_Send(&rows, 1, MPI_INT, dest, mtype, MPI_COMM_WORLD);
         MPI_Send(&a[offset][0], rows*NCA, MPI_DOUBLE, dest, mtype,
                   MPI_COMM_WORLD);
         MPI_Send(&b, NCA*NCB, MPI_DOUBLE, dest, mtype, MPI_COMM_WORLD);
         offset = offset + rows;
      }

      /* wait for results from all worker tasks */
      mtype = FROM_WORKER;
      for (i=1; i<=numworkers; i++)
      {
         source = i;
         MPI_Recv(&offset, 1, MPI_INT, source, mtype, MPI_COMM_WORLD, &status);
         MPI_Recv(&rows, 1, MPI_INT, source, mtype, MPI_COMM_WORLD, &status);
         MPI_Recv(&c[offset][0], rows*NCB, MPI_DOUBLE, source, mtype, MPI_COMM_WORLD, &status);
      }

      /* print results */
      printf("Here is the result matrix\n");
      for (i=0; i<NRA; i++)
      {
         printf("\n"); 
         for (j=0; j<NCB; j++) 
            printf("%6.2f   ", c[i][j]);
      }
      printf ("\n");
   }

/**************************** worker task ************************************/
   if (taskid > MASTER)
   {
      mtype = FROM_MASTER;
      MPI_Recv(&offset, 1, MPI_INT, MASTER, mtype, MPI_COMM_WORLD, &status);
      MPI_Recv(&rows, 1, MPI_INT, MASTER, mtype, MPI_COMM_WORLD, &status);
      MPI_Recv(&a, rows*NCA, MPI_DOUBLE, MASTER, mtype, MPI_COMM_WORLD, &status);
      MPI_Recv(&b, NCA*NCB, MPI_DOUBLE, MASTER, mtype, MPI_COMM_WORLD, &status);

      for (k=0; k<NCB; k++)
         for (i=0; i<rows; i++)
         {
            c[i][k] = 0.0;
            for (j=0; j<NCA; j++)
               c[i][k] = c[i][k] + a[i][j] * b[j][k];
         }
      mtype = FROM_WORKER;
      MPI_Send(&offset, 1, MPI_INT, MASTER, mtype, MPI_COMM_WORLD);
      MPI_Send(&rows, 1, MPI_INT, MASTER, mtype, MPI_COMM_WORLD);
      MPI_Send(&c, rows*NCB, MPI_DOUBLE, MASTER, mtype, MPI_COMM_WORLD);
   }
   MPI_Finalize();
}