/*This has been created by Mohammad Hammoud.
 *CMUQ- Nov. 8, 2012.
 * */
#include <stdio.h>
#include <mpi.h>

#define array_size 20
#define num_elem_pp 10
#define sendTag 1
#define recvTag 2

int array_send[array_size];
int array_recv[num_elem_pp];


int main(int argc, char **argv){

	int myPID;
	int num_procs;
	int sum = 0;
	int partial_sum = 0;	
	double startTime = 0.0;
	double endTime;
	MPI_Status status;


	MPI_Init(&argc, &argv);
	MPI_Comm_rank(MPI_COMM_WORLD, &myPID);
	MPI_Comm_size(MPI_COMM_WORLD, &num_procs);

	if(myPID == 0 )
	{
		startTime = MPI_Wtime();

		int i;
		for(i= 0; i < array_size; i++)
			array_send[i] = i;

		int j;
		for(j = 1; j < num_procs; j++){
			int start_elem = j * num_elem_pp;			

			MPI_Send(&array_send[start_elem], num_elem_pp, MPI_INT, j, sendTag, MPI_COMM_WORLD);
		}

		int k;
		for(k=0; k < num_elem_pp; k++)
  			sum += array_send[k];

		int l;
		for(l = 1; l < num_procs; l++){

			MPI_Recv(&partial_sum, 1, MPI_INT, MPI_ANY_SOURCE, recvTag, MPI_COMM_WORLD, &status);

			printf("Partial sum received from process %d = %d\n", l, status.MPI_SOURCE);

			sum += partial_sum;
			 
		}
	
		

		endTime = MPI_Wtime();

		printf("Grand Sum = %d and time taken = %f\n", sum, (endTime-startTime));	

	
	}else{

		
		MPI_Recv(&array_recv, num_elem_pp, MPI_INT, 0, sendTag, MPI_COMM_WORLD, &status);

	
		int i;
		for(i = 0; i < num_elem_pp; i++)
			partial_sum += array_recv[i];

		MPI_Send(&partial_sum, 1, MPI_INT, 0, recvTag, MPI_COMM_WORLD);


	}


	MPI_Finalize();

}