Q. Addition of array elements using two processors?

In this example we have to find sum of all elements of an array A of size n. We will divide n elements in 2 groups of roughly equivalent size. The first [n/2] elements are added by first processor P₀ and last [n/2] elements by 2^nd processor P₁.  The two sums then are added to obtain 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);

}