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

#define NOT_DONE       0
#define DONE           1
#define NO_TAG         2
#define WORK_PER_SLAVE 100000

int main(int argc, char **argv)
{
int        server,slave,total_slaves;
int        total_rand,r,i,tag;
int        destination,sum,sum_slaves;
int        size,rank,slave_rank;
double     average;
MPI_Comm   world,slaves;
MPI_Status status;

/* Initializations */
MPI_Init(&argc,&argv);
world=MPI_COMM_WORLD;
MPI_Comm_size(world,&size);
if( size < 2)
{
	printf("\nUnable to run in less than 2 processes...\n\n");
	MPI_Abort(world,1);
}
MPI_Comm_rank(world,&rank);
/* Define slave communicator */
server=0;
slave=( rank == server );
MPI_Comm_split(world,slave,0,&slaves);

/* Master */

if( rank == server )
{
	total_slaves=size-1;
	total_rand=0;
	srand(time(NULL));
	do
	{
		MPI_Recv(&r,1,MPI_INT,MPI_ANY_SOURCE,MPI_ANY_TAG,world,&status);
		tag=status.MPI_TAG;
		if( tag != DONE )
		{
			r=1 + (int)( 10.0 * rand() / ( RAND_MAX + 1.0 ) );
			destination=status.MPI_SOURCE;
			MPI_Send(&r,1,MPI_INT,destination,NO_TAG,world);
			++total_rand;
		}
		else
			--total_slaves;
	}
	while(total_slaves);
	MPI_Barrier(world);
	MPI_Recv(&sum,1,MPI_INT,MPI_ANY_SOURCE,MPI_ANY_TAG,world,&status);
	average=(double)sum/(double)total_rand;
	printf("\nAverage=%e\n\n",average);
}
else

/* Slave */

{
	r=0;
	sum_slaves=0;
	for(i=0;i<WORK_PER_SLAVE;++i)
	{
		MPI_Send(&r,1,MPI_INT,server,NOT_DONE,world);
		MPI_Recv(&r,1,MPI_INT,server,NO_TAG,world,&status);
		sum_slaves+=r;
	}
	MPI_Send(&r,1,MPI_INT,server,DONE,world);
	MPI_Reduce(&sum_slaves,&sum,1,MPI_INT,MPI_SUM,0,slaves);
	MPI_Barrier(world);
	MPI_Comm_rank(slaves,&slave_rank);
	if( slave_rank == 0 )
	{
		MPI_Send(&sum,1,MPI_INT,server,NO_TAG,world);
	}	
}
MPI_Finalize();
return 0;
}