/******************************************************************************
* 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)
* LAST REVISED: 12/14/95 Blaise Barney
******************************************************************************/
#include "mpi.h"
#include <stdio.h>
#define NRA 1000           /* number of rows in matrix A */
#define NCA 1000          /* number of columns in matrix A */
#define NCB 1000         /* 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 */
	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 */
double	startwtime,endwtime;
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 ("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;

      startwtime=MPI_Wtime();
      /* 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);
      }
      endwtime=MPI_Wtime();
      printf("mxm time = %f  %f Mflops\n",endwtime-startwtime, 2.*NCA*NCB*NRA/(endwtime-startwtime)*1.e-6);

      /* 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();
}