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Subject: Re: [OMPI devel] PLM consistency: priority
From: Jeff Squyres (jsquyres_at_[hidden])
Date: 2008-07-17 07:35:37


FWIW -- we talked about this a bunch in the Louisville and have some
ideas. More details coming in meeting wrapup notes...

On Jul 11, 2008, at 11:14 AM, Ralph H Castain wrote:

> Ummm...I actually was talking about the "PLM", not the "PML".
>
> But I believe what you suggest concurs with what I said. In the PLM,
> you
> could still provide multiple components you want considered, though
> it has
> less meaning there. My suggestion really is only that we eliminate the
> params to adjust relative priority as they are just confusing the
> user and
> potentially misleading them as to what is going to happen.
>
> Ralph
>
>
>
> On 7/11/08 9:07 AM, "Aurélien Bouteiller" <bouteill_at_[hidden]>
> wrote:
>
>> We don't want the user to have to select by hand the best PML. The
>> logic inside the current selection process selects the best pml for
>> the underlying network. However changing the priority is pretty
>> meaningless from the user's point of view. So while retaining the
>> selection process including priorities, we might want to remove the
>> priority parameter, and use only the pml=ob1,cm syntax from the
>> user's
>> point of view.
>>
>> Aurelien
>>
>> Le 11 juil. 08 à 10:56, Ralph H Castain a écrit :
>>
>>> Okay, another fun one. Some of the PLM modules use MCA params to
>>> adjust
>>> their relative selection priority. This can lead to very unexpected
>>> behavior
>>> as which module gets selected will depend on the priorities of the
>>> other
>>> selectable modules - which changes from release to release as people
>>> independently make adjustments and/or new modules are added.
>>>
>>> Fortunately, this doesn't bite us too often since many environments
>>> only
>>> support one module, and since there is nothing to tell the user that
>>> the plm
>>> module whose priority they raised actually -didn't- get used!
>>>
>>> However, in the interest of "least astonishment", some of us working
>>> on the
>>> RTE had changed our coding approach to avoid this confusion. Given
>>> that we
>>> have this nice mca component select logic that takes the specified
>>> module -
>>> i.e., "-mca plm foo" always yields foo if it can run, or errors out
>>> if it
>>> can't - then the safest course is to remove MCA params that adjust
>>> module
>>> priorities and have the user simply tell us which module they want
>>> us to
>>> use.
>>>
>>> Do we want to make this consistent, at least in the PLM? Or do you
>>> want to
>>> leave the user guessing? :-)
>>>
>>> Ralph
>>>
>>>
>>> _______________________________________________
>>> devel mailing list
>>> devel_at_[hidden]
>>> http://www.open-mpi.org/mailman/listinfo.cgi/devel
>>
>>
>> _______________________________________________
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>
>
>
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-- 
Jeff Squyres
Cisco Systems