Global variables in MPI c++

Hello,

I am writing an mpi code. I want one variable to be writable and readable by all threads.

#include <mpi.h>
#include <stdio.h>
#include <fstream>
#include <iostream>
#include <string>
#include <vector>
#include <stdlib.h>
#include <algorithm>
#include <unistd.h>

using namespace std;

//Defining the GLOBAL variable I need
int COMPLETE=0;

int main(int argc, char * argv[])
{
    
    MPI::Init(argc, argv);

    //MPI job

    //Updating GLOBAL variable
    COMPLETE++;

    if (COMPLETE==Vector.size())
    {
       //Do something
    }
    MPI::Finalize();

    return 0;

}

Code like above does not work since COMPLETE variable is used independantly in all classes. What I want is to update this variable by ++1 every time a thread finishes.

My question is:
1/ How can I set I global variable for MPI?
2/ How should I synchronyze writing permissions for this variable

Thank you for your time.
SDA

PanGalactic (1658)

This is not really a "General C++ Programming" question. While you may get a useful answer here, you are much more likely to get such questions answered on a forum dedicated to MPI programming.

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Global variables in MPI c++

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