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Subject: Re: [OMPI users] (no subject)
From: Jeff Squyres (jsquyres_at_[hidden])
Date: 2008-05-27 15:56:11


On May 27, 2008, at 9:33 AM, Gabriele Fatigati wrote:

> Great, it works!
> Thank you very very much.
> But, can you explain me how this parameter works?

You might want to have a look at this short video for a little
background on some relevant OpenFabrics concepts:

     http://www.open-mpi.org/video/?category=openfabrics#openfabrics-concepts

In v1.2, for short messages, OMPI will sometimes copy your message to
a pre-posted receive buffer, and immediately mark the MPI request as
"complete". Depending on the timing and current network resource
usage, the message may or may not have been given to the network stack
yet (e.g., if we're out of flow control credits to send to this
particular peer). If your application keeps dipping down into the MPI
layer frequently, this situation will almost certainly resolve itself
once the receiver becomes active or other events occur to free up
available resources. As such, the early completion optimization
pretty much depends on frequent calls to MPI. Without them, since
OMPI currently has no independent progression (e.g., a progress
thread), your message will wait until OMPI's internal progress engine
is tripped again.

Hope that helps.

>
> On Thu, 15 May 2008 21:40:45 -0400, Jeff Squyres said:
>>
>> Sorry this message escaped for so long it got buried in my INBOX.
>> The
>> problem you're seeing might be related to one we just answered
>> about a
>> similar situation:
>>
>> http://www.open-mpi.org/community/lists/users/2008/05/5657.php
>>
>> See if using the pml_ob1_use_early_completion flag works for you.
>>
>>
>>
>> On Apr 30, 2008, at 7:05 AM, Gabriele FATIGATI wrote:
>>
>>> Hi,
>>> i tried to run SkaMPI benchmark on IBM-BladeCenterLS21-BCX system
>>> with 256 processors, but test has stopped on "AlltoAll-length"
>>> routine, with count=8192 for some reasons.
>>>
>>> I have launched test with:
>>> --mca btl_openib_eager_limit 1024
>>>
>>> Same tests with 128 processor or less, have finished successful.
>>>
>>> Different values of eager limit dont' solve the problem. Thanks in
>>> advance.
>>> --------------------------
>>> Gabriele Fatigati
>>>
>>> CINECA Systems & Tecnologies Department
>>>
>>> Supercomputing Group
>>>
>>> Via Magnanelli 6/3, Casalecchio di Reno (BO) Italy
>>>
>>> www.cineca.it Tel: 39 051 6171722
>>>
>>> g.fatigati_at_[hidden]
>>> _______________________________________________
>>> users mailing list
>>> users_at_[hidden]
>>> http://www.open-mpi.org/mailman/listinfo.cgi/users
>>
>>
>> --
>> Jeff Squyres
>> Cisco Systems
>>
>> _______________________________________________
>> users mailing
> --------------------------
> Gabriele Fatigati
>
> CINECA Systems & Tecnologies Department
>
> Supercomputing Group
>
> Via Magnanelli 6/3, Casalecchio di Reno (BO) Italy
>
> www.cineca.it Tel: 39 051 6171722
>
> g.fatigati_at_[hidden]
> _______________________________________________
> users mailing list
> users_at_[hidden]
> http://www.open-mpi.org/mailman/listinfo.cgi/users

-- 
Jeff Squyres
Cisco Systems