#include "mpi.h" 
#include <stdio.h> 
#define SIZE 4
 int main(argc,argv) 
int argc; char *argv[]; 
{
 int i,numtasks, rank, sendcount, recvcount, source; 
       float sendbuf[SIZE] ; 
       float recvbuf[SIZE][SIZE];
              MPI_Init(&argc,&argv);
              MPI_Comm_rank(MPI_COMM_WORLD, &rank); 
              MPI_Comm_size(MPI_COMM_WORLD,&numtasks);
              for (i=0; i<SIZE;i++)
                  sendbuf[i]=SIZE*rank+i+1; 
              if (numtasks == SIZE) 
              { source = 1; 
              sendcount = SIZE; 
              recvcount = SIZE;
              MPI_Gather(sendbuf,sendcount,MPI_FLOAT,recvbuf,recvcount, 
                                             MPI_FLOAT,source,MPI_COMM_WORLD); 
              if(rank == 1)
                     {printf("rank= %d \n Results:",rank);
                     for (i=0;i<4;i++)printf(" %f %f %f %f\n",
                                 recvbuf[i][0], recvbuf[i][1],recvbuf[i][2],
                                             recvbuf[i][3]); 
                      }
       
} 
              else  printf("Must specify %d processors. Terminating.\n",SIZE); 
       MPI_Finalize(); 
}