[mpich-discuss] create group and communicator failed for RMA

Sufeng Niu sniu at hawk.iit.edu
Thu Jul 18 16:02:50 CDT 2013


in my mpi program, I create 3 groups and communicators:

        forward_rank = (int *)malloc((numprocs-1) * sizeof(int));
        backward_rank = (int *)malloc((numprocs-1) * sizeof(int));
        comp_rank = (int *)malloc((numprocs-2) * sizeof(int));

        for (i=0; i<numprocs-1; i++){
                backward_rank[i] = i+1;
                forward_rank[i] = i;
        for (i=0; i<numprocs-2; i++){
                comp_rank[i] = i+1;

        MPI_Group global_group, fgroup, bgroup, cgroup;     // forward
group, backward group, computation group
forward, backward, computation communicator
        MPI_Comm_group(MPI_COMM_WORLD, &global_group);

        MPI_Group_incl(global_group, numprocs-1, forward_rank, &bgroup);
        MPI_Comm_create(MPI_COMM_WORLD, bgroup, &MPI_BACK_WORLD);

        MPI_Group_incl(global_group, numprocs-1, backward_rank, &fgroup);
        MPI_Comm_create(MPI_COMM_WORLD, fgroup, &MPI_FOR_WORLD);

        MPI_Group_incl(global_group, numprocs-2, comp_rank, &cgroup);
        MPI_Comm_create(MPI_COMM_WORLD, cgroup, &MPI_COMP_WORLD);

And I used them for my RMA operation

So in my main function transfer new communicator to another c file as:
udp_sub(win, &MPI_FOR_WORLD);

image_sub(rank, win, strip_buff, &MPI_FOR_WORLD, &MPI_BACK_WORLD,

in udp_sub and image_sub function:

I called:
MPI_Win_create(image_buff, 2*image_info->image_size*sizeof(uint16),
sizeof(uint16), MPI_INFO_NULL, *MPI_FOR_WORLD, win);

but I got the error when I execute them:
MPI_Win_create(189): MPI_Win_create(base=0x7fe50c06c010, size=9216000,
disp_unit=2, MPI_INFO_NULL, MPI_COMM_NULL, win=0x1a5e940) failed
MPI_Win_create(116): Null communicator

I already transfer the communicator address to it, but I don't understand
why communicator is null. or I did in a wrong way? Any suggestions are
appreciate. Thank you!
Best Regards,
Sufeng Niu
ECASP lab, ECE department, Illinois Institute of Technology
Tel: 312-731-7219
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