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

[Thakur, Rajeev]

Does it happen with other MPI implementations?

Rajeev

-----Original Message-----
From: "Mccall, Kurt E. (MSFC-EV41) via discuss" <discuss at mpich.org <mailto:discuss at mpich.org>>
Reply-To: "discuss at mpich.org <mailto:discuss at mpich.org>" <discuss at mpich.org <mailto:discuss at mpich.org>>
Date: Friday, September 15, 2023 at 9:43 AM
To: "discuss at mpich.org <mailto:discuss at mpich.org>" <discuss at mpich.org <mailto:discuss at mpich.org>>
Cc: "Mccall, Kurt E. (MSFC-EV41)" <kurt.e.mccall at nasa.gov <mailto:kurt.e.mccall at nasa.gov>>
Subject: Re: [mpich-discuss] Buffer corruption due to an excessive number of messages


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 <mailto:discuss at mpich.org>>
Sent: Thursday, September 14, 2023 3:10 PM
To: discuss at mpich.org <mailto:discuss at mpich.org>
Cc: Joachim Jenke <jenke at itc.rwth-aachen.de <mailto: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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