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Subject: Re: [OMPI devel] [RFC] mca_base_open() NULL
From: Jeff Squyres (jsquyres_at_[hidden])
Date: 2008-05-08 11:00:37

On May 8, 2008, at 9:32 AM, Josh Hursey wrote:

> I think 'all' would be a nice symmetric addition to complement 'none'
> and then this would allow users to specify the "select best from all
> available" option on the command line.

Ok, if you accept "all" and "none" as friendly ammendments to your
RFC, I think I'm done with input there. :-)

Any other comments on the RFC?

> Disallowing the NULL default string I think would have some
> repercussions throughout the code requiring a change in the way we use
> MCA parameters. For example, many component selection logics use the
> NULL value as the current 'select best from all' indicator. Other MCA
> parameters take the NULL value to indicate that the user did not set
> any value for this string parameter and thus it can be ignored. Maybe
> we can try to add a deprecation warning message when this happens to
> gauge it's frequency.

There's no burning need to do this ASAP; let's add this to the list of
items to talk about in the tech meeting. Perhaps one of us could do a
little prep before the meeting to figure out:

- how often NULL is given as a default OMPI MCA string param (probably
quite often) -- easy enough to find out by putting a counter/
opal_output in the string registration function

- how often NULL is *required* by the logic for one reason or another
(probably a little more tricky to count)

Jeff Squyres
Cisco Systems