If buffers overlap, use memmov and not memcpy:
Good point, you would have to use memmov in general for overlapping source and target buffers. I was thinking of the special case where the source and target buffers are identical.
I don’t think so. It’s an incorrect program to get from a buffer to itself. MPICH is being helpful is catching this user error.
Do you know where in the standard this is specified? I'm having trouble finding it. -Nick ________________________________________ From: Boisvert, Sebastien [[email protected]] Sent: Thursday, August 21, 2014 7:30 PM To: [email protected] Subject: Re: [mpich-discuss] MPI_Get on the same memory location
________________________________________ From: Nick Radcliffe [[email protected]] Sent: Thursday, August 21, 2014 5:47 PM To: [email protected] Subject: Re: [mpich-discuss] MPI_Get on the same memory location
MPIR_Localcopy(357): memcpy arguments alias each other, dst=0x19a5f40 src=0x19a5f40 len=4 It looks like memcpy is doing a check to make sure the source and destination buffers don't overlap. This seems like a bug to me -- when doing an MPI_Get from a buffer to itself, the implementation should probably just do nothing and return.
I disagree. If buffers overlap, use memmov and not memcpy: " If copying takes place between objects that overlap, the behavior is undefined." --source: http://pubs.opengroup.org/onlinepubs/009695399/functions/memcpy.html Also: http://stackoverflow.com/questions/1960991/which-one-to-use-memmove-or-memcp...
-Nick ________________________________________ From: [email protected] [[email protected]] on behalf of Alessandro Fanfarillo [[email protected]] Sent: Thursday, August 21, 2014 5:25 PM To: [email protected] Subject: [mpich-discuss] MPI_Get on the same memory location Dear all, I'm having the following error: Fatal error in MPI_Get: Internal MPI error!, error stack: MPI_Get(156).......: MPI_Get(origin_addr=0x19a5f40, origin_count=4, MPI_BYTE, target_rank=0, target_disp=0, target_count=4, MPI_BYTE, win=0xa0000000) failed MPIDI_Get(247).....: MPIR_Localcopy(357): memcpy arguments alias each other, dst=0x19a5f40 src=0x19a5f40 len=4 if I try to execute MPI_Get on the same memory location on a shared memory machine (my laptop). I cannot find anything in the standard that denies it for the one-sided. Running with OpenMPI everything works fine. Is it a bug or I missed something in the standard? Thanks. Alessandro -- Alessandro Fanfarillo Dip. di Ingegneria Civile ed Ingegneria Informatica Università di Roma "Tor Vergata" NCAR Office: +1 (303) 497-2442 Tel: +39-06-7259 7719 _______________________________________________ discuss mailing list [email protected] To manage subscription options or unsubscribe: https://lists.mpich.org/mailman/listinfo/discuss _______________________________________________ discuss mailing list [email protected] To manage subscription options or unsubscribe: https://lists.mpich.org/mailman/listinfo/discuss
discuss mailing list [email protected] To manage subscription options or unsubscribe: https://lists.mpich.org/mailman/listinfo/discuss