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

#define NMAX 100000

int main(int argc, char *argv[]) { 
    int 	rank,ncpu,num0,num1,i;
    float	data0[NMAX],data1[NMAX];
    MPI_Status	status;

/* Basic Initialisation */
    MPI_Init(&argc,&argv); 
    MPI_Comm_rank(MPI_COMM_WORLD,&rank);
    MPI_Comm_size(MPI_COMM_WORLD,&ncpu);

/* Check there are enough processes */
    if (ncpu==1) {
	printf("Need at least two processes\n");
	MPI_Finalize();
	return 0;
    }

/* Parse the command-line */
    num0=100;
    num1=100;

    if (argc>1) {
	num0=atoi(argv[1]);
	if (num0<1)    num0=1;
	if (num0>NMAX) num0=NMAX;
	num1=num0;
    }
	
    if (argc>2) {
	num1=atoi(argv[2]);
	if (num1<1)    num1=1;
	if (num1>NMAX) num1=NMAX;
    }

/* Instructions for Process 0 */
    if (rank==0) {
        for (i=0;i<num0;i++) {
	    data0[i]=i*i;
	}

	MPI_Send(&data0,num0,MPI_FLOAT,1,100,MPI_COMM_WORLD);
	printf("Process %d sent %d floats\n",rank,num0);

	MPI_Recv(&data1,num1,MPI_FLOAT,1,200,MPI_COMM_WORLD,&status);
	printf("Process %d received %d floats\n",rank,num1);
    }

/* Instructions for Process 1 */
    if (rank==1) {
        for (i=0;i<num1;i++) {
	    data1[i]=sqrt((float)i);
	}

	MPI_Send(&data1,num1,MPI_FLOAT,0,200,MPI_COMM_WORLD);
	printf("Process %d sent %d floats\n",rank,num1);

	MPI_Recv(&data0,num0,MPI_FLOAT,0,100,MPI_COMM_WORLD,&status);
	printf("Process %d received %d floats\n",rank,num0);
    }

    MPI_Finalize(); 
    return 0; 
}