#include "mpi.h" 
#include <stdio.h> 
 int main(argc,argv) 
int argc; char *argv[]; 
{
 int i,numtasks, rank, count, source; 
       MPI_Status stat;
       float sendbuf,sum ; 
       float recvbuf;
              MPI_Init(&argc,&argv);
              MPI_Comm_rank(MPI_COMM_WORLD, &rank); 
              MPI_Comm_size(MPI_COMM_WORLD,&numtasks);
              count = 1; 

              /*  recv ranks from all the tasks */

              if(rank==0){
                   sum=0.0;
                   for(i=1; i< numtasks;i++){
                          MPI_Recv(&recvbuf,count,MPI_FLOAT,i,i,MPI_COMM_WORLD,&stat);
                          sum=sum+recvbuf;
                                             }
                         }
                else {
                       sendbuf=(float)rank;
                       MPI_Send(&sendbuf,count,MPI_FLOAT,0,rank,MPI_COMM_WORLD);
                     }

             /* send the sum to all the tasks */

              if(rank==0){
                   for(i=1; i< numtasks;i++){
                          MPI_Send(&sum,count,MPI_FLOAT,i,i,MPI_COMM_WORLD);
                                             }
                         }
                else {
                       MPI_Recv(&sum,count,MPI_FLOAT,0,rank,MPI_COMM_WORLD,&stat);
                     }
                     printf("rank= %d SUM:%f\n ",rank,sum);
       MPI_Finalize(); 
}