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 _______________________________________________ discuss mailing list [email protected] To manage subscription options or unsubscribe: https://lists.mpich.org/mailman/listinfo/discuss