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

#define NUM_OF_ELEMENTS 100
#define NUM_PER_PROCESS 25
#define ROOT 0

int main (int argc, char** argv) {
	
	int myRank; 
	int numProcs;
	
	int sendBuffer[NUM_OF_ELEMENTS];
	int recvBuffer[NUM_PER_PROCESS];
	
	MPI_Init(&argc, &argv);
	
	MPI_Comm_rank(MPI_COMM_WORLD, &myRank);
	MPI_Comm_size(MPI_COMM_WORLD, &numProcs);
	
	if (myRank == ROOT)
	{
		int i;
		for (i=0; i<NUM_OF_ELEMENTS; i++)
			sendBuffer[i] = i;		
	}
	
	MPI_Scatter(sendBuffer, NUM_PER_PROCESS,
		MPI_INT, recvBuffer, NUM_PER_PROCESS,
		MPI_INT, ROOT, MPI_COMM_WORLD);
	
	int partialSum = 0;
	int j;
	for (j=0; j<NUM_PER_PROCESS; j++)
		partialSum += recvBuffer[j];
	
	int totalSum = 0;
	
	MPI_Reduce(&partialSum, &totalSum, 1, MPI_INT, MPI_SUM, 
		ROOT, MPI_COMM_WORLD);
		
	if (myRank == ROOT)	
		printf("Total sum: %d.\n", totalSum);	
		
	MPI_Finalize();
	
	return 0; 
		
	
}