Good catch. I will take a look and see how best to fix this. -Nathan
On Tue, Aug 26, 2014 at 07:03:24PM +0300, Lisandro Dalcin wrote:
> I finally managed to track down some issues in mpi4py's test suite
> using Open MPI 1.8+. The code below should be enough to reproduce the
> problem. Run it under valgrind to make sense of my following
> diagnostics.
>
> In this code I'm creating a 2D, periodic Cartesian topology out of
> COMM_SELF. In this case, the process in COMM_SELF has 4 logical in/out
> links to itself. So we have size=1 but indegree=outdegree=4. However,
> in ompi/mca/coll/basic/coll_basic_module.c, "size * 2" request are
> being allocated to manage communication:
>
> if (OMPI_COMM_IS_INTER(comm)) {
> size = ompi_comm_remote_size(comm);
> } else {
> size = ompi_comm_size(comm);
> }
> basic_module->mccb_num_reqs = size * 2;
> basic_module->mccb_reqs = (ompi_request_t**)
> malloc(sizeof(ompi_request_t *) * basic_module->mccb_num_reqs);
>
> I guess you have to also special-case for topologies and allocate
> indegree+outdegree requests (not sure about this number, just
> guessing).
>
>
> #include <stdio.h>
> #include <mpi.h>
>
> int main(int argc, char *argv[])
> {
> MPI_Comm comm;
> int ndims = 2, dims[2] = {1,1}, periods[2] = {1,1};
> int sendbuf = 7, recvbuf[5] = {0,0,0,0,0};
> MPI_Init(&argc, &argv);
>
> MPI_Cart_create(MPI_COMM_SELF, ndims, dims, periods, 0, &comm);
>
> MPI_Neighbor_allgather(&sendbuf, 1, MPI_INT,
> recvbuf, 1, MPI_INT,
> comm);
>
> {int i; for (i=0;i<5;i++) printf("%d ",recvbuf[i]); printf("\n");}
>
> MPI_Finalize();
> return 0;
> }
>
>
> --
> Lisandro Dalcin
> ============
> Research Scientist
> Computer, Electrical and Mathematical Sciences & Engineering (CEMSE)
> Numerical Porous Media Center (NumPor)
> King Abdullah University of Science and Technology (KAUST)
> http://numpor.kaust.edu.sa/
>
> 4700 King Abdullah University of Science and Technology
> al-Khawarizmi Bldg (Bldg 1), Office # 4332
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>
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> Link to this post:
> http://www.open-mpi.org/community/lists/devel/2014/08/15713.php
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