[mpich-discuss] New communicator and MPI_Reduce...

Pavan Balaji balaji at mcs.anl.gov
Tue Nov 13 09:10:46 CST 2012

On 11/13/2012 08:31 AM US Central Time, Alejandro Allievi wrote:
> However, when I want to apply the reduction operation using the new
> communicator as
>     MPI_Reduce(&test_newcomm, &sum_newcomm, 1, MPI_INT, MPI_SUM, 0,
> first_row_comm);
> It compiles fine but throws an execution error:
> Fatal error in PMPI_Reduce: Invalid communicator, error stack:
> PMPI_Reduce(1270): MPI_Reduce(sbuf=000000000022FE38,
> rbuf=000000000022FE30, count=1, MPI_INT, MPI_SUM, root=0,
> MPI_COMM_NULL) failed
> PMPI_Reduce(1160): Null communicator
> But communicator " first_row_comm " is properly create. Is this a bug
> or I'm doing something wrong with the way I'm passing the
> new communicator argument in MPI_Reduce, or...??

It looks like you didn't create first_row_comm correctly.

 -- Pavan

Pavan Balaji

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