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Subject: Re: [OMPI devel] [RFC] mca_base_open() NULL
From: Jeff Squyres (jsquyres_at_[hidden])
Date: 2008-05-08 07:50:36


- I think "none" is a slightly better word than "null" for this value;
"none" implies that you don't open anything, whereas "null" could be a
specific component (as it is/was in some frameworks).

- Whatever word we decide on will need to become a reserved component
name (i.e., no components will be able to use that as their name). We
should adjust and friends to ensure that no component has
this name (not difficult -- just make abort if it finds a
component of this name).

- Is this value supposed to be accessible/usable by users, or is it
meant to only be used internally?

--> If intended to be used by users, I marginally prefer a single,
lower case, simple word (e.g., "none") vs. a caps word -- it's easier
to type and is consistent with our other values. I recognize that we
don't want users to use the value by accident, and making it all caps
makes it stand out, but I think the consistency issues are more

--> If not intended to be used by users (i.e., it's an internal
mechanism only), is there a reason why we're not using a zero-length
string (e.g., mpirun --mca foo "")?

On May 6, 2008, at 2:09 PM, Josh Hursey wrote:

> What: Add a MCA-NULL option to open no components in mca_base_open()
> Why: Sometimes we do not want to open or select any components of
> a framework.
> Where: patch attached for current trunk.
> When: Needs further discussion.
> Timeout: Unknown. [May 13, 2008 (After teleconf)?]
> Short Version:
> --------------
> This RFC is intended to continue discussion on the thread started
> here:
> Discussion should occur on list, but maybe try to come to some
> settlement on this RFC in the next week or two.
> Longer Version:
> ---------------
> Currently there is no way to express to the MCA system that
> absolutely no components of a framework are needed and therefore
> nothing should be opened. The addition of a sentinel value is needed
> to explicitly express this intention. It was suggested that if a
> 'MCA-NULL' value is passed as an argument for a framework then this
> should be taken to indicate such an intention.
> <mca-null.diff>
> _______________________________________________
> devel mailing list
> devel_at_[hidden]

Jeff Squyres
Cisco Systems