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. — Pavan On Aug 21, 2014, at 7:10 PM, Nick Radcliffe <[email protected]> wrote:

I didn't mean there was a bug in memcpy. I meant the bug was in MPI_Get, which should indeed be checking that pointers are not aliased.

-Nick

From: Brian Van Straalen [[email protected]] Sent: Thursday, August 21, 2014 6:21 PM To: [email protected] Subject: Re: [mpich-discuss] MPI_Get on the same memory location

It depends on what version of memcpy you are using. If you are calling IEEE std 1003.1 2004 then memcpy is defined as

void *memcpy(void *restrict s1, const void *restrict s2, size_t n);

so this form of calling memcpy is illegal and the error from memcpy is correct.

The routine calling memcpy should verify you are not aliased, or incorrect behavior is very likely on newer architectures. It would be better to check for aliased data before calling memcpy.

Brian Van Straalen

On Aug 21, 2014, at 3:47 PM, Nick Radcliffe <[email protected]> wrote:

...

...

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.

-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

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-- Pavan Balaji ✉️ http://www.mcs.anl.gov/~balaji