// ==================================================================
// Author: Jean-Michel Richer
// Email: jean-michel.richer@univ-angers.fr
// Date: Aug 2020
// Last modified: November 2020
// Purpose: Demonstrate basic send functionality, send array of float
// from master (rank=0) to slave (rank=1)
// ==================================================================
#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); 
	
	if (p.is_master()) { 
		// Code of master
		
		// set remote cpu identifier that will communicate with master
		p.remote(1);
		
		// processor of id 0 (master) fills and sends the array
		data_size = 100 + rand() % 100;
		data = new float [data_size];
		for (int i=0; i<data_size; ++i) data[i] = i+1;
		
		// 1- send size of array to remote
		p.send(data_size);
		
		
		// 2- send data of array to remote and receive result
		float result = 0;
		p.sendrecv(data, data_size, result);	
		
		p << "result is " << result << " for length=" << data_size;
		p << ", expected=" << (data_size * (data_size+1))/ 2  << endl;
		
		delete [] data;		
		
	} else if (p.id() == 1) {
		// Code for slave
		
		// tells to Process to send data to master processor 
		p.remote(0);
		
		// process of id 1 will receive the array and compute the sum
		// 1- we receive the array length and allocate space
		p.recv(data_size);
	
		data = new float[data_size];
		
		// 2- we receive the data 
		p.recv(data, data_size);
		
		// 3- compute sum
		float sum = 0;
		for (int i=0; i<data_size; ++i) {
			sum += data[i];
		}
		
		// 4- send back result
		p.send(sum);
		
		delete [] data;
		
	} else {
		// other process (if any) won't do anything
		p << "is idle" << endl; 
	}
   
   	sleep(1);
   	
   	p.logs(cout);
   	
   	// desctuctor of Process p will call the finalize method
   	// of MPI
}

// ==============================================================
// version C++
// ============================================================== 
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);
}