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Subject: Re: [OMPI devel] PLM consistency: priority
From: Ralph H Castain (rhc_at_[hidden])
Date: 2008-07-11 11:14:01

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.


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
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