Hi there, I tried to understand the behavior Thatyene said and I think is a bug in open mpi implementation.

I do not know what exactly is happening because I am not an expert in ompi code, but I could see that when one process define its color as MPI_UNDEFINED, one of the processes on the inter-communicator blocks in the call to the function bellow:

/* Step 3: set up the communicator                           */
    /* --------------------------------------------------------- */
    /* Create the communicator finally */
    rc = ompi_comm_set ( &newcomp,           /* new comm */
                         comm,               /* old comm */
                         my_size,            /* local_size */
                         lranks,             /* local_ranks */
                         my_rsize,           /* remote_size */
                         rranks,             /* remote_ranks */
                         NULL,               /* attrs */
                         comm->error_handler,/* error handler */
                         (pass_on_topo)?
                         (mca_base_component_t *)comm->c_topo_component:
                         NULL,               /* topo component */
                         NULL,               /* local group */
                         NULL                /* remote group */
    );

This function is called inside ompi_comm_split, in the file ompi/communicator/comm.c

Is there a solution for this problem in some revision? I insist in this problem because I need to use this function for a similar purpose.

Any idea?


On Wed, Jan 25, 2012 at 4:50 PM, Thatyene Louise Alves de Souza Ramos <thatyene@gmail.com> wrote:
It seems the split is blocking when must return MPI_COMM_NULL, in the case I have one process with a color that does not exist in the other group or with the color = MPI_UNDEFINED.

On Wed, Jan 25, 2012 at 4:28 PM, Rodrigo Oliveira <rsilva.oliveira@gmail.com> wrote:
Hi Thatyene,

I took a look in your code and it seems to be logically correct. Maybe there is some problem when you call the split function having one client process with color = MPI_UNDEFINED. I understood you are trying to isolate one of the client process to do something applicable only to it, am I wrong? According to open mpi documentation, this function can be used to do that, but it is not working. Anyone have any idea about what can be?

Best regards

Rodrigo Oliveira


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