I have an application I am trying to run on a Cray machine composed of XE6 nodes. I have run this application previously using Open MPI and MVAPICH on a few different machines, so I think it should be more or less free of major bugs. However, when I run it on the Cray machine, I get a segmentation fault with a stack trace that ends in this: #0 0x00002aaaafe265e6 in memcpy () from /lib64/libc.so.6 #1 0x00002aaaae8fe023 in MPID_Segment_index_m2m () from /opt/cray/lib64/libmpich_gnu_48.so.2 #2 0x00002aaaae8fca18 in MPID_Segment_manipulate () from /opt/cray/lib64/libmpich_gnu_48.so.2 #3 0x00002aaaae9049d1 in MPID_Segment_unpack () from /opt/cray/lib64/libmpich_gnu_48.so.2 #4 0x00002aaaae8edd38 in MPID_nem_gni_complete_rdma_get () from /opt/cray/lib64/libmpich_gnu_48.so.2 #5 0x00002aaaae8e11c8 in MPID_nem_gni_check_localCQ () from /opt/cray/lib64/libmpich_gnu_48.so.2 #6 0x00002aaaae8e29fa in MPID_nem_gni_poll () from /opt/cray/lib64/libmpich_gnu_48.so.2 #7 0x00002aaaae8c3515 in MPIDI_CH3I_Progress () from /opt/cray/lib64/libmpich_gnu_48.so.2 #8 0x00002aaaae9a3d4d in PMPI_Testsome () from /opt/cray/lib64/libmpich_gnu_48.so.2 I understand that this is very little information to go on, but I really cannot deal with this problem, and I thought I would try this list while I am trying to solicit help from our support team. Currently, I do not have access to a debug version of the library (or the source code). Has anyone here seen a similar error? What would be a reason to get an error on memcpy in MPICH while calling MPI_Testsome in general? I do have asserts in my code to make sure that the output arrays are large enough, and I got it to work on other implementations of MPI, so I am really clueless to what the problem might be. Thank you, Marcin