Thanks for the replies and sorry for the incomplete information. I should have written that I get a segfault for np=2 but not np=1. Find the exact error message below. I've also tried the program Jeff sent and I get the same segfault as before for all np>1. I'll try to checkout and build the development version and see if I can reproduce.

===================================================================================
=   BAD TERMINATION OF ONE OF YOUR APPLICATION PROCESSES
=   PID 7703 RUNNING AT 30-9-81.wireless.csail.mit.edu
=   EXIT CODE: 11
=   CLEANING UP REMAINING PROCESSES
=   YOU CAN IGNORE THE BELOW CLEANUP MESSAGES
===================================================================================
YOUR APPLICATION TERMINATED WITH THE EXIT STRING: Segmentation fault: 11 (signal 11)
This typically refers to a problem with your application.
Please see the FAQ page for debugging suggestions


On Tue, Jul 26, 2016 at 12:16 PM, Jeff Hammond <jeff.science@gmail.com> wrote:
Indeed, Rob is right.  I only tested np<=2.  Didn't see failure until nproc=16 because of how malloc works but in any case, it is trivial to fix this by allocating C to be nproc elements.

Jeff

#include <mpi.h>

#include <stdio.h>

#include <stdlib.h>


int main(int argc, char *argv[])

{

    MPI_Init(&argc, &argv);


    MPI_Comm comm = MPI_COMM_WORLD;

    uint64_t *A, *C;

    int rnk, siz;


    MPI_Comm_rank(comm, &rnk);

    MPI_Comm_size(comm, &siz);

    A = calloc(1, sizeof(uint64_t));

    C = calloc(siz, sizeof(uint64_t));

    A[0] = rnk + 1;


    MPI_Allgather(A, 1, MPI_UINT64_T, C, 1, MPI_UINT64_T, comm);


    free(C);

    free(A);


    MPI_Finalize();

    return 0;

}


On Tue, Jul 26, 2016 at 9:00 AM, Rob Latham <robl@mcs.anl.gov> wrote:


On 07/26/2016 10:17 AM, Andreas Noack wrote:
On my El Capitan macbook I get a segfault when running the program below
with more than a single process but only when MPICH has been compiled
with Clang.

I don't get that good debug info but here is some of what I got


 valgrind is pretty good at sussing out these sorts of things:

==18132== Unaddressable byte(s) found during client check request
==18132==    at 0x504D1D7: MPIR_Localcopy (helper_fns.c:84)
==18132==    by 0x4EC8EA1: MPIR_Allgather_intra (allgather.c:169)
==18132==    by 0x4ECA5EC: MPIR_Allgather (allgather.c:791)
==18132==    by 0x4ECA7A4: MPIR_Allgather_impl (allgather.c:832)
==18132==    by 0x4EC8B5C: MPID_Allgather (mpid_coll.h:61)
==18132==    by 0x4ECB9F7: PMPI_Allgather (allgather.c:978)
==18132==    by 0x4008F5: main (noack_segv.c:18)
==18132==  Address 0x6f2f138 is 8 bytes after a block of size 16 alloc'd
==18132==    at 0x4C2FB55: calloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==18132==    by 0x4008B0: main (noack_segv.c:15)
==18132==
==18132== Invalid write of size 8
==18132==    at 0x4C326CB: memcpy@@GLIBC_2.14 (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==18132==    by 0x504D31B: MPIR_Localcopy (helper_fns.c:84)
==18132==    by 0x4EC8EA1: MPIR_Allgather_intra (allgather.c:169)
==18132==    by 0x4ECA5EC: MPIR_Allgather (allgather.c:791)
==18132==    by 0x4ECA7A4: MPIR_Allgather_impl (allgather.c:832)
==18132==    by 0x4EC8B5C: MPID_Allgather (mpid_coll.h:61)
==18132==    by 0x4ECB9F7: PMPI_Allgather (allgather.c:978)
==18132==    by 0x4008F5: main (noack_segv.c:18)
==18132==  Address 0x6f2f138 is 8 bytes after a block of size 16 alloc'd
==18132==    at 0x4C2FB55: calloc (in /usr/lib/valgrind/vgpreload_memcheck-amd64-linux.so)
==18132==    by 0x4008B0: main (noack_segv.c:15)



     MPI_Comm_rank(comm, &rnk);
     A = calloc(1, sizeof(uint64_t));
     C = calloc(2, sizeof(uint64_t));
     A[0] = rnk + 1;

     MPI_Allgather(A, 1, MPI_UINT64_T, C, 1, MPI_UINT64_T, comm);

 Your 'buf count tuple' is ok for A: every process sends one uint64

your 'buf count tuple' is too small for C if there are any more than 2 proceses .

When you say "more than one"... do you mean 2?

==rob

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