Attached is the message list for rank 0 for the communication step that is failing. There are about 160 isends and irecvs. The ‘message size’ is actually
a number of cells. On some steps only one 8-byte word per cell is communicated, at another step we exchange 7 words, and another step we exchange 21 words. You can see the smallest is 10 cells, the largest around 1000 cells.
Thus for the 7-word communication step, the smallest messages are 560 bytes, the largest are 56000 bytes, and there is a distribution of sizes. For the single-word
communication step, the size distribution would be from 80 bytes to 8000 and for the 21-word step it would be from 1680 to 168000 bytes.
From: firstname.lastname@example.org [mailto:email@example.com]
On Behalf Of Rolf vandeVaart
Sent: Thursday, June 27, 2013 9:02 AM
To: Open MPI Users
Subject: EXTERNAL: Re: [OMPI users] Application hangs on mpi_waitall
Ed, how large are the messages that you are sending and receiving?
It ran a bit longer but still deadlocked. All matching sends are posted 1:1with posted recvs so it is a delivery issue of some kind. I'm running a debug compiled version tonight to see what that might turn up. I may try to rewrite with
blocking sends and see if that works. I can also try adding a barrier (irecvs, barrier, isends, waitall) to make sure sends are not buffering waiting for recvs to be posted.
Sent via the Samsung Galaxy S™ III, an AT&T 4G LTE smartphone
-------- Original message --------
From: George Bosilca <firstname.lastname@example.org>
To: Open MPI Users <email@example.com>
Subject: Re: [OMPI users] Application hangs on mpi_waitall
Im not sure but there might be a case where the BTL is getting overwhelmed by the nob-blocking operations while trying to setup the connection. There is a simple test for this. Add an MPI_Alltoall with a reasonable size (100k) before you start posting the non-blocking
receives, and let's see if this solves your issue.
On Jun 26, 2013, at 04:02 , firstname.lastname@example.org wrote:
> An update: I recoded the mpi_waitall as a loop over the requests with
> mpi_test and a 30 second timeout. The timeout happens unpredictably,
> sometimes after 10 minutes of run time, other times after 15 minutes, for
> the exact same case.
> After 30 seconds, I print out the status of all outstanding receive
> requests. The message tags that are outstanding have definitely been
> sent, so I am wondering why they are not getting received?
> As I said before, everybody posts non-blocking standard receives, then
> non-blocking standard sends, then calls mpi_waitall. Each process is
> typically waiting on 200 to 300 requests. Is deadlock possible via this
> implementation approach under some kind of unusual conditions?
> Thanks again,
>> I'm running OpenMPI 1.6.4 and seeing a problem where mpi_waitall never
>> returns. The case runs fine with MVAPICH. The logic associated with the
>> communications has been extensively debugged in the past; we don't think
>> it has errors. Each process posts non-blocking receives, non-blocking
>> sends, and then does waitall on all the outstanding requests.
>> The work is broken down into 960 chunks. If I run with 960 processes (60
>> nodes of 16 cores each), things seem to work. If I use 160 processes
>> (each process handling 6 chunks of work), then each process is handling 6
>> times as much communication, and that is the case that hangs with OpenMPI
>> 1.6.4; again, seems to work with MVAPICH. Is there an obvious place to
>> start, diagnostically? We're using the openib btl.
>> users mailing list
> users mailing list
users mailing list
This email message is for the sole use of the intended recipient(s) and may contain confidential information. Any unauthorized review, use, disclosure or distribution is prohibited. If you are not the intended recipient, please contact
the sender by reply email and destroy all copies of the original message.