#include <unistd.h>
#include <iostream>
#include <cstdlib>
#include <unistd.h> // for sleep
#include <sstream>
#include <numeric>
using namespace std;
#include <mpi.h>

 
// ==============================================================
// version C++
// ==============================================================
 
int main(int argc, char ** argv) {
	// maximum number of CPUs
	int max_cpus;
	// cpu identifier (called rank)
	int cpu_rank;
	// C-string to store name of the host
	char cpu_name[MPI::MAX_PROCESSOR_NAME];
	// length of the C-string
	int length;

	// initialization also using command line parameters
	MPI::Init(argc, argv);

	// get number of programs running
	max_cpus = MPI::COMM_WORLD.Get_size();
	
	// get program identifier
	cpu_rank = MPI::COMM_WORLD.Get_rank();
	
	// get cpu name
	memset(cpu_name, 0, MPI::MAX_PROCESSOR_NAME);
	MPI::Get_processor_name(cpu_name, length);
 
	cerr << cpu_rank << "/" << max_cpus << " on machine " << cpu_name << endl;
	
	// data to exchange
	int send_data;
	int recv_data;
	
	// identifier (rank) of remove processor (master or slave)
	int remote_cpu, source_cpu;
	
	// Status for communication
	MPI::Status status;
	int TAG_0 = 0;

	if (cpu_rank == 0) {
		
		remote_cpu = 1;
		send_data = 11111;

	} else if (cpu_rank == 1) {
		
		remote_cpu = 0; 
		send_data = 22222;
		
	} 

	MPI::COMM_WORLD.Sendrecv(
        &send_data,   // Send buffer
        1,            // Number of elements to send
        MPI::INT,     // Datatype of send elements
        remote_cpu,   // Destination rank
        0,            // Send tag
        &recv_data,   // Receive buffer
        1,            // Number of elements to receive
        MPI::INT,     // Datatype of receive elements
        remote_cpu,   // Source rank
        0,            // Receive tag
        status        // Status object
    );
	
   
	if (cpu_rank == 0) {
		
		cerr << "Master: recv_data=" << recv_data << endl;
		
	} else if (cpu_rank == 1) {
		
		cerr << "Slave: recv_data=" << recv_data << endl;

	}
	MPI::Finalize();
 
	exit(EXIT_SUCCESS);
}