// ==================================================================
// Author: Jean-Michel Richer
// Date: Aug 2020
// Last modified: November 2020
// Purpose: Use of MPI::Gather 
// Each process creates its own local data and they are all send
// to the master process (of rank 0)
// ==================================================================
#include <unistd.h>
#include <iostream>
#include <cstdlib>
#include <unistd.h> // for sleep
#include <sstream>
using namespace std;
#include "ezmpi.h"
using namespace ez::mpi;

/**
 * run master and slaves
 */
void run(int argc, char *argv[]) {

	// data to send
	float *data;
	int data_size;

	// Create Process from ezmpi
	// that retrives cpu rank (id), # cpus (max), cpu name (name)
	Process p(argc, argv); 
	
	const int local_data_size = 10;
	int *local_data;
	int global_data_size = 0;
	int *global_data = NULL;
	
	// each processor creates its local data
	local_data = new int [ local_data_size ];
	for (int i=0; i<local_data_size; ++i) {
		local_data[i] = (p.id() * 10) + i + 1;
	}
		
	p << "local array=[";
	for (int i=0; i<local_data_size; ++i) {
		p << local_data[i] << " ";
	}
	p << "]" << endl;
	
	if (p.is_master()) {
		// master process will gather data from others
		global_data_size = p.max() * local_data_size ;
		global_data = new int [ global_data_size ];
		for (int i=0; i<global_data_size; ++i) global_data[i] = 0;
	}
	
	p.gather(local_data, local_data_size, global_data);
	
	if (p.is_master()) {
		p << "global array = [";
		for (int i=0; i<global_data_size; ++i) { 
			p << global_data[i] << " ";
		}
		p << "]" << endl;;
	}
	
	sleep(1);
   	
   	p.logs(cout);
}
	
// ==================================================================
// C++ version
// ==================================================================
int main(int argc, char ** argv) {
 	// call a function that contains code for master and slave
	// in order to avoid problems of initialization and finalization
	run(argc, argv);
	
	exit(EXIT_SUCCESS);
}