[mpich-discuss] Buffer corruption due to an excessive number of messages

[Mccall, Kurt E. (MSFC-EV41)]

Joachim,

Unfortunately, using MPI_Improbe/MPI_Mrecv didn't solve the problem -- I still am receiving buffers with invalid data objects near the ends of the buffers.   The problem goes away when I reduce the size of the job (number of nodes), making me think it is the large number of messages  that is causing the problem.

1. Is there a way to detect this kind of overload with an MPI call?
2. Is there an upper bound on the number of messages that can be "in flight"?
3. Is there a upper bound on message length?

Or is there some other possible cause that I haven't thought of?

Thanks,
Kurt

-----Original Message-----
From: Joachim Jenke via discuss <discuss at mpich.org>
Sent: Thursday, September 14, 2023 3:10 PM
To: discuss at mpich.org
Cc: Joachim Jenke <jenke at itc.rwth-aachen.de>
Subject: [EXTERNAL] [BULK] Re: [mpich-discuss] Buffer corruption due to an excessive number of messages

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Hi Kurt,

just a thought: do you execute single-threaded or multi-threaded?

In case of multi-threaded execution, you should look into MPI_Improbe/MPI_Mrecv just to make sure that you really receive the message you probed for.
Even in single-threaded execution you might try whether using these functions instead fixes your issue.

Best
Joachim

Am 14.09.23 um 22:02 schrieb Mccall, Kurt E. (MSFC-EV41) via discuss:
> It seems that when I send a process too many non-blocking messages
> (with
> MPI_Isend) , MPI_Iprobe/MPI_Recv sometimes returns a buffer
>
> with corrupted data for some of the messages.   Usually the corrupted
> data objects are at the end of the array that was sent.  I checked the
>
> buffers passed to MPI_Isend, and they are uncorrupted.
>
>  1. Is there a way to detect this kind of overload with an MPI call?
>  2. Is there an upper bound on the number of messages that can be "in
>     flight"?
>  3. Is there a upper bound on message length?
>
> Thanks,
>
> Kurt
>
>
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Dr. rer. nat. Joachim Jenke

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