Programming Based on Message Passing

As we know, the programming model based on message passing uses high level programming languages like C/C++ along with a number of message passing libraries like PVM and MPI. Here, given an example program of message passing.

Example 1: Addition of array elements using two processors.

In this problem, we have to search the sum of all the elements of an array A of size n. We shall separate n elements into two groups of roughly equal size. The first [n/2] elements are added by the first processor, P0, and last [n/2] elements the by second processor, P1. The two sums then are added to get the final result. The program is given below:

Program for P0

#include

#define n 100

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

int A[n];

int sum0 =0, sum1=0,sum; MPI_Init(&argc, &argv);

for( int i=0;i

scanf("%d", &A[i]);

MPI_Send( &n/2, n/2, MPI_INT,1, 0, MPI_COMM_WORLD);

for(i=1; i

sum0+=A[i];

sum1=MPI_Recv(&n/2, n/2, MPI_INT,1, 0, MPI_COMM_WORLD);

sum=sum0+sum1; printf("%d",sum); MPI_Finalize();

}

Program for P1,

int func( int B[int n])

{

MPI_Recv(&n/2, n/2, MPI_INT,0, 0, MPI_COMM_WORLD);

int sum1=0 ;

for (i=0; i

sum1+=B[i];

MPI_Send( 0, n/2, MPI_INT,0, 0, MPI_COMM_WORLD);

}