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Matrix multiplication using MPI
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| /********************************************************************** | |
| * MPI-based matrix multiplication AxB=C | |
| *********************************************************************/ | |
| #include <stdio.h> | |
| #include "mpi.h" | |
| #define N 4 /* number of rows and columns in matrix */ | |
| MPI_Status status; | |
| double a[N][N],b[N][N],c[N][N]; | |
| main(int argc, char **argv) | |
| { | |
| int numtasks,taskid,numworkers,source,dest,rows,offset,i,j,k; | |
| struct timeval start, stop; | |
| MPI_Init(&argc, &argv); | |
| MPI_Comm_rank(MPI_COMM_WORLD, &taskid); | |
| MPI_Comm_size(MPI_COMM_WORLD, &numtasks); | |
| numworkers = numtasks-1; | |
| /*---------------------------- master ----------------------------*/ | |
| if (taskid == 0) { | |
| for (i=0; i<N; i++) { | |
| for (j=0; j<N; j++) { | |
| a[i][j]= 1.0; | |
| b[i][j]= 2.0; | |
| } | |
| } | |
| gettimeofday(&start, 0); | |
| /* send matrix data to the worker tasks */ | |
| rows = N/numworkers; | |
| offset = 0; | |
| for (dest=1; dest<=numworkers; dest++) | |
| { | |
| MPI_Send(&offset, 1, MPI_INT, dest, 1, MPI_COMM_WORLD); | |
| MPI_Send(&rows, 1, MPI_INT, dest, 1, MPI_COMM_WORLD); | |
| MPI_Send(&a[offset][0], rows*N, MPI_DOUBLE,dest,1, MPI_COMM_WORLD); | |
| MPI_Send(&b, N*N, MPI_DOUBLE, dest, 1, MPI_COMM_WORLD); | |
| offset = offset + rows; | |
| } | |
| /* wait for results from all worker tasks */ | |
| for (i=1; i<=numworkers; i++) | |
| { | |
| source = i; | |
| MPI_Recv(&offset, 1, MPI_INT, source, 2, MPI_COMM_WORLD, &status); | |
| MPI_Recv(&rows, 1, MPI_INT, source, 2, MPI_COMM_WORLD, &status); | |
| MPI_Recv(&c[offset][0], rows*N, MPI_DOUBLE, source, 2, MPI_COMM_WORLD, &status); | |
| } | |
| gettimeofday(&stop, 0); | |
| printf("Here is the result matrix:\n"); | |
| for (i=0; i<N; i++) { | |
| for (j=0; j<N; j++) | |
| printf("%6.2f ", c[i][j]); | |
| printf ("\n"); | |
| } | |
| fprintf(stdout,"Time = %.6f\n\n", | |
| (stop.tv_sec+stop.tv_usec*1e-6)-(start.tv_sec+start.tv_usec*1e-6)); | |
| } | |
| /*---------------------------- worker----------------------------*/ | |
| if (taskid > 0) { | |
| source = 0; | |
| MPI_Recv(&offset, 1, MPI_INT, source, 1, MPI_COMM_WORLD, &status); | |
| MPI_Recv(&rows, 1, MPI_INT, source, 1, MPI_COMM_WORLD, &status); | |
| MPI_Recv(&a, rows*N, MPI_DOUBLE, source, 1, MPI_COMM_WORLD, &status); | |
| MPI_Recv(&b, N*N, MPI_DOUBLE, source, 1, MPI_COMM_WORLD, &status); | |
| /* Matrix multiplication */ | |
| for (k=0; k<N; k++) | |
| for (i=0; i<rows; i++) { | |
| c[i][k] = 0.0; | |
| for (j=0; j<N; j++) | |
| c[i][k] = c[i][k] + a[i][j] * b[j][k]; | |
| } | |
| MPI_Send(&offset, 1, MPI_INT, 0, 2, MPI_COMM_WORLD); | |
| MPI_Send(&rows, 1, MPI_INT, 0, 2, MPI_COMM_WORLD); | |
| MPI_Send(&c, rows*N, MPI_DOUBLE, 0, 2, MPI_COMM_WORLD); | |
| } | |
| MPI_Finalize(); | |
| } |
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