[mpich-discuss] [mvapich-discuss] How many Groups ?

[Krishna Kandalla]

Hi,
   We recently received the following post and we seem to have the
same behavior with mpich2-1.5a1. We realize that this is because we are
running out
of context id's. Do you folks think it is feasible to increase the range of
allowable context id's?


   The following code can be used to reproduce this behavior:

---------------------------------------------------------

#include <mpi.h>
#include <stdlib.h>

int main(int argc, char **argv)
{
   int num_groups = 1000, my_rank, world_size, *group_members, i;
   MPI_Group orig_group, *groups;
   MPI_Init(&argc, &argv);
   MPI_Comm *comms;

   if ( argc > 1 ) num_groups=atoi(argv[1]);

   MPI_Comm_rank( MPI_COMM_WORLD, &my_rank );
   MPI_Comm_size(MPI_COMM_WORLD, &world_size);
   MPI_Comm_group(MPI_COMM_WORLD, &orig_group);

   group_members = calloc(sizeof(int), world_size);
   groups = calloc(sizeof(MPI_Group), num_groups);
   comms = calloc(sizeof(MPI_Comm), num_groups);

   for ( i = 0; i < world_size; ++i ) group_members[i] = i;

   for ( i = 0; i < num_groups; ++i )
   {
       MPI_Group_incl(orig_group, world_size, group_members, &groups[i]);
       MPI_Comm_create(MPI_COMM_WORLD, groups[i], &comms[i]);
   }
}

The observed error is :
PMPI_Comm_create(656).........:
MPI_Comm_create(MPI_COMM_WORLD, group=0xc80700f6, new_comm=0x1d1ecd4) failed
PMPI_Comm_create(611).........:
MPIR_Comm_create_intra(266)...:
MPIR_Get_contextid(554).......:
MPIR_Get_contextid_sparse(785): Too many communicators
[cli_0]: aborting job:



Thanks,
Krishna


On Thu, Feb 23, 2012 at 1:32 PM, Lewis Alderton <lalderto at us.ibm.com> wrote:

>
> I'm using MPI_Group_incl to create many groups. There seems to be limit of
> 2048 groups - any way to increase this number ?
>
> ( I'm using mvapich2-1.8a1p1 )
>
> Thanks.
>
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>
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