/*
 * Prime1.c
 * prost ciji je prvi neparni naslednik takodje prost
 *
 *  Created on: Aug 20, 2010
 *      Author: djordje
 */

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

const int A = 10000000;

int prime(int n)
{
	if((n == 0) || (n == 1)) return 0;            
        if(n == 2) return 1;
	for(int i = 2; i <= sqrt(n); i++) if((n % i) == 0) return 0;

	return 1;
}

int main(int argc, char *argv[])
{
	int i, solutions, globalSolution;
	int id; //Process rank
	int p; //Num of processes
	double elapsed_time;
	int *primes, *globalPrimes;

	MPI_Init(&argc, &argv);
	MPI_Barrier(MPI_COMM_WORLD);
	elapsed_time = - MPI_Wtime();
	MPI_Comm_rank(MPI_COMM_WORLD, &id);
	MPI_Comm_size(MPI_COMM_WORLD, &p);
	
	primes = (int*) calloc(A, sizeof( int ));
	for(i = 2*id+1; i < A; i += 2*p) primes[i] = prime(i);

	globalPrimes = (int*) malloc(A * sizeof( int ));
	MPI_Allreduce(primes, globalPrimes, A, MPI_INT, MPI_LOR, MPI_COMM_WORLD);

	solutions = 0;
	for(i = 2 * id + 1; i < A; i += 2*p)
		if(globalPrimes[i] && globalPrimes[i+2]) solutions++;
	
	MPI_Reduce(&solutions, &globalSolution, 1 , MPI_INT, MPI_SUM, 0, MPI_COMM_WORLD);
	elapsed_time += MPI_Wtime();
	MPI_Finalize();
	
	if(id == 0)printf("%d, Elapsed time is %f\n", globalSolution, elapsed_time);
	return 0;
}