C program written using MPI which passes an integer through processes in a cyclic (ring like) pattern.

MPI_RING

#include <stdio.h>
#include <mpi.h>

int main(int argc,char *argv[])
{
    int myid, numprocs;
    int tag,source,destination,count;
    int buffer;
    MPI_Status status;
 
    MPI_Init(&argc,&argv);
    MPI_Comm_size(MPI_COMM_WORLD,&numprocs);
    MPI_Comm_rank(MPI_COMM_WORLD,&myid);
    count=1;
    if(myid == 0){
	  	printf("Enter an integer:\t");
    	   	scanf("%d",&buffer);
      		MPI_Send(&buffer,count,MPI_INT,myid+1,1,MPI_COMM_WORLD);
		printf("process %d  sent %d to %d\n",myid,buffer,myid+1);
		MPI_Recv(&buffer,count,MPI_INT,numprocs-1,1,MPI_COMM_WORLD,&status);
      		printf("process %d received %d from %d \n",myid,buffer,numprocs-1);
    		}
    else if(myid==numprocs-1){
		MPI_Recv(&buffer,count,MPI_INT,myid-1,1,MPI_COMM_WORLD,&status);
      		printf("process %d received %d from %d \n",myid,buffer,myid-1);
		MPI_Send(&buffer,count,MPI_INT,0,1,MPI_COMM_WORLD);
		printf("process %d  sent %d to %d\n",myid,buffer,0);
	
    		}
     else {
		MPI_Recv(&buffer,count,MPI_INT,myid-1,1,MPI_COMM_WORLD,&status);
		printf("process %d received %d from %d \n",myid,buffer,myid-1);
		MPI_Send(&buffer,count,MPI_INT,myid+1,1,MPI_COMM_WORLD);
      		printf("process %d  sent %d to %d\n",myid,buffer,myid+1);
	  	}	
    
    MPI_Finalize();
    return 0;
}