This information is insufficient to blame the compiler. We don't know if the user (application code), MPICH, or gcc is doing something wrong. First, you need to use a stable compiler version (not trunk) and a recent MPICH (3.2 not the old 3.1 version). Second, you need to make sure the user code is not doing something wrong (e.g. MPI_Alltoall could have gotten an invalid buffer address or count). If you send us a toy program that reproduces the problem, we could help with this. --Halim www.mcs.anl.gov/~aamer On 4/6/16 10:24 AM, VandeVondele Joost wrote:

Hi,

when compiling mpich-3.1.2 using gcc trunk (which will be gcc 6.0 in a couple of days/weeks), I noticed mpich gets miscompiled when building with CFLAGS='-O2 -ftree-vectorize -g' (but not with just -O2 -g or -O3 -g).

I believe that the miscompilation happens with the macro MPIDI_Request_create_sreq since a typical trace looks like:

Program received signal SIGSEGV: Segmentation fault - invalid memory reference.

Backtrace for this error: #0 0x33ac83269f in ??? #1 0x7f3743953d69 in MPIDI_Isend_self at src/mpid/ch3/src/mpidi_isend_self.c:34 #2 0x7f374394dfa3 in MPID_Isend at src/mpid/ch3/src/mpid_isend.c:55 #3 0x7f374390793a in MPIC_Isend at src/mpi/coll/helper_fns.c:646 #4 0x7f37438628c5 in MPIR_Alltoall_intra at src/mpi/coll/alltoall.c:520 #5 0x7f374386376e in MPIR_Alltoall at src/mpi/coll/alltoall.c:726 #6 0x7f3743863827 in MPIR_Alltoall_impl at src/mpi/coll/alltoall.c:761 #7 0x7f3743863e7a in PMPI_Alltoall at src/mpi/coll/alltoall.c:884 #8 0x7f37424181bf in pmpi_alltoall_ at src/binding/fortran/mpif_h/alltoallf.c:272

I don't know mpich well enough to extract a testcase, but it would be great if somebody could extract that and report to the gcc team (I'm happy to do the reporting if needed).

thanks in advance,

Joost

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