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

#define NUMBER_OF_PROCS 4
#define NUMBER_OF_ELEMENTS 1000
#define NUMBER_OF_ELEMENTS_PER_PROCESS 250

#define ROOT 0

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

	int partialSum = 0;
	int finalSum = 0;
	
	int sendBuffer[NUMBER_OF_ELEMENTS];
	int recvBuffer[NUMBER_OF_ELEMENTS_PER_PROCESS];
	
	MPI_Init(&argc, &argv);
	
	MPI_Comm_rank(MPI_COMM_WORLD, &myRank);
	
	printf("My rank: %d\n", myRank);
	
	if (myRank == ROOT) {
		
		// Master
		int i;
		for (i = 0; i < NUMBER_OF_ELEMENTS; i++)
			sendBuffer[i] = i+1;
	}
	
	MPI_Scatter(sendBuffer, NUMBER_OF_ELEMENTS_PER_PROCESS, MPI_INT, recvBuffer, 
		NUMBER_OF_ELEMENTS_PER_PROCESS, MPI_INT, ROOT, MPI_COMM_WORLD);
	
	int j;
	for (j = 0; j < NUMBER_OF_ELEMENTS_PER_PROCESS; j++) 
		partialSum += recvBuffer[j];
	
	MPI_Reduce(&partialSum, &finalSum, 1, MPI_INT, MPI_SUM, ROOT, MPI_COMM_WORLD);
	
	if (myRank == ROOT) 
		printf("Final sum: %d\n", finalSum);
	
	MPI_Finalize();
	
	return 1;	
	
}