[OMPI users] MPI_CANCEL

[slimtimmy]

I encountered some problems when using MPI_CANCEL. I call
Request::Cancel followed by Request::Wait to ensure that the request has
been cancelled. However Request::Wait does not return when I send bigger
messages. The following code should reproduce this behaviour:
#include "mpi.h"
#include <iostream>

using namespace std;

enum Tags
{
    TAG_UNMATCHED1,
    TAG_UNMATCHED2
};

int main()
{
    MPI::Init();

    const int rank = MPI::COMM_WORLD.Get_rank();
    const int numProcesses = MPI::COMM_WORLD.Get_size();
    const int masterRank = 0;

    if (rank == masterRank)
    {
        cout << "master" << endl;
        const int numSlaves = numProcesses - 1;
        for(int i = 0; i < numSlaves; ++i)
        {
            const int slaveRank = i + 1;
            int buffer;
            MPI::COMM_WORLD.Recv(&buffer, 1, MPI::INT, slaveRank,
                TAG_UNMATCHED1);
        }

    }
    else
    {
        cout << "slave " << rank << endl;
        //const int size = 1;
        const int size = 10000;
        int buffer[size];
        MPI::Request request = MPI::COMM_WORLD.Isend(buffer, size, 
MPI::INT,
            masterRank, TAG_UNMATCHED2);

        cout << "slave ("<< rank<<"): sent data" << endl;

        request.Cancel();

        cout << "slave ("<< rank<<"): cancel issued" << endl;

        request.Wait();

        cout << "slave ("<< rank<<"): finished" << endl;
    }


    MPI::Finalize();

    return 0;
}


If I set size to 1, everything works as expected, the slave process
finishes execution. However if I use a bigger buffer (in this case
10000) the wait blocks forever. That's the output of the program when
run with two processes:

master
slave 1
slave (1): sent data
slave (1): cancel issued


Have I misinterpreted the standard? Or does Request::Wait block until
the message is delievered?