CODEWITHSUNDEEP
cmpi
Gaurav Singh
Gaurav Singh

Reputation: 456

MPI_ERR_RANK: invalid rank

I got the above mentioned error on running the following program in C. The program uses 3-d hypercube topology to find sum of all elements of an 8-element array. It uses MPI library.:

#include<stdio.h>
#include<mpi.h>

int main(int argc, char **argv)
{
    int rank, n, src, dest;
    MPI_Init(&argc, &argv);
    MPI_Status status;
    MPI_Comm_rank(MPI_COMM_WORLD, &rank);
    MPI_Comm_size(MPI_COMM_WORLD, &n);
    int tag = 100;
    int receive;
    int array[8] = {10, 20, 30, 40, 50, 60, 70, 80};

    if (rank&1 == 1)
        MPI_Send(&array[rank], 1, MPI_INT, rank-1, tag, MPI_COMM_WORLD);
    else
    {
        MPI_Recv(&receive, 1, MPI_INT, rank+1, tag, MPI_COMM_WORLD, &status);
        array[rank] += receive;
        if (rank&2 == 1)
            MPI_Send(&array[rank], 1, MPI_INT, rank-2, tag, MPI_COMM_WORLD);
        else
        {
            MPI_Recv(&receive, 1, MPI_INT, rank+2, tag, MPI_COMM_WORLD, &status);
            array[rank] += receive;
            if (rank&4 == 1)
                MPI_Send(&array[rank], 1, MPI_INT, rank-4, tag, MPI_COMM_WORLD);
            else
            {
                MPI_Recv(&receive, 1, MPI_INT, rank+4, tag, MPI_COMM_WORLD, &status);
                array[rank] += receive;
                printf("\n%d \n", array[0]);
            }
        }
    }
    MPI_Finalize();
    return 0;
}

Used 8 processes by calling 

mpirun -n 8 ./a.out

Runtime error message: 

An error occurred in MPI_Recv  
reported by process [3153068033,6]  
on communicator MPI_COMM_WORLD  
MPI_ERR_RANK: invalid rank  
MPI_ERRORS_ARE_FATAL (processes in this communicator will now abort,  
and potentially your MPI job)

Upvotes: 4

Views: 9266

Answers (1)

Gilles Gouaillardet
Gilles Gouaillardet

Reputation: 8395

It looks like an error in the way you use bitwise and.

For example, it should be

if (rank & 2)

instead of

if (rank&2 == 1)

rank&2 is a bitwise and, which means its value is either 0 or 2 (and it is never 1)

Upvotes: 2

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