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Subject: Re: [OMPI devel] regression with derived datatypes
From: George Bosilca (bosilca_at_[hidden])
Date: 2014-05-07 13:23:16


Strange. The outcome and the timing of this issue seems to highlight a link with the other datatype-related issue you reported earlier, and as suggested by Ralph with Gilles scif+vader issue.

Generally speaking, the mechanism used to split the data in the case of multiple BTLs, is identical to the one used to split the data in fragments. So, if the culprit is in the splitting logic, one might see some weirdness as soon as we force the exclusive usage of the send protocol, with an unconventional fragment size.

In other words using the following flags “—mca btl tcp,self —mca btl_tcp_flags 3 —mca btl_tcp_rndv_eager_limit 23 —mca btl_tcp_eager_limit 23 —mca btl_tcp_max_send_size 23” should always transfer wrong data, even when only one single BTL is in play.

  George.

On May 7, 2014, at 13:11 , Rolf vandeVaart <rvandevaart_at_[hidden]> wrote:

> OK. So, I investigated a little more. I only see the issue when I am running with multiple ports enabled such that I have two openib BTLs instantiated. In addition, large message RDMA has to be enabled. If those conditions are not met, then I do not see the problem. For example:
> FAILS:
> Ø mpirun –np 2 –host host1,host2 –mca btl_openib_if_include mlx5_0:1,mlx5_0:2 –mca btl_openib_flags 3 MPI_Isend_ator_c
> PASS:
> Ø mpirun –np 2 –host host1,host2 –mca btl_openib_if_include mlx5_0:1 –mca btl_openib_flags 3 MPI_Isend_ator_c
> Ø mpirun –np 2 –host host1,host2 –mca btl_openib_if_include_mlx5:0:1,mlx5_0:2 –mca btl_openib_flags 1 MPI_Isend_ator_c
>
> So we must have some type of issue when we break up the message between the two openib BTLs. Maybe someone else can confirm my observations?
> I was testing against the latest trunk.
>
> Rolf
>
> From: devel [mailto:devel-bounces_at_[hidden]] On Behalf Of Joshua Ladd
> Sent: Wednesday, May 07, 2014 10:48 AM
> To: Open MPI Developers
> Subject: Re: [OMPI devel] regression with derived datatypes
>
> Rolf,
>
> This was run on a Sandy Bridge system with ConnectX-3 cards.
>
> Josh
>
>
> On Wed, May 7, 2014 at 10:46 AM, Joshua Ladd <jladd.mlnx_at_[hidden]> wrote:
> Elena, can you run your reproducer on the trunk, please, and see if the problem persists?
>
> Josh
>
>
> On Wed, May 7, 2014 at 10:26 AM, Jeff Squyres (jsquyres) <jsquyres_at_[hidden]> wrote:
> On May 7, 2014, at 10:03 AM, Elena Elkina <elena.elkina_at_[hidden]> wrote:
>
> > Yes, this commit is also in the trunk.
>
> Yes, I understand that -- my question is: is this same *behavior* happening on the trunk. I.e., is there some other effect on the trunk that is causing the bad behavior to not occur?
>
> > Best,
> > Elena
> >
> >
> > On Wed, May 7, 2014 at 5:45 PM, Jeff Squyres (jsquyres) <jsquyres_at_[hidden]> wrote:
> > Is this also happening on the trunk?
> >
> >
> > Sent from my phone. No type good.
> >
> > On May 7, 2014, at 9:44 AM, "Elena Elkina" <elena.elkina_at_[hidden]> wrote:
> >
> >> Sorry,
> >>
> >> Fixes #4501: Datatype unpack code produces incorrect results in some case
> >>
> >> ---svn-pre-commit-ignore-below---
> >>
> >> r31370 [[BR]]
> >> Reshape all the packing/unpacking functions to use the same skeleton. Rewrite the
> >> generic_unpacking to take advantage of the same capabilitites.
> >>
> >> r31380 [[BR]]
> >> Remove a non-necessary label.
> >>
> >> r31387 [[BR]]
> >> Correctly save the displacement for the case where the convertor is not
> >> completed. As we need to have the right displacement at the beginning
> >> of the next call, we should save the position relative to the beginning
> >> of the buffer and not to the last loop.
> >>
> >> Best regards,
> >> Elena
> >>
> >>
> >> On Wed, May 7, 2014 at 5:43 PM, Jeff Squyres (jsquyres) <jsquyres_at_[hidden]> wrote:
> >> Can you cite the branch and SVN r number?
> >>
> >> Sent from my phone. No type good.
> >>
> >> > On May 7, 2014, at 9:24 AM, "Elena Elkina" <elena.elkina_at_[hidden]> wrote:
> >> >
> >> > b531973419a056696e6f88d813769aa4f1f1aee6
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>
> --
> Jeff Squyres
> jsquyres_at_[hidden]
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