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Subject: Re: [OMPI devel] RFC: convert send to ssend
From: Jeff Squyres (jsquyres_at_[hidden])
Date: 2009-08-24 13:27:41

On Aug 24, 2009, at 12:14 PM, Ashley Pittman wrote:

> > - compiled out
> > - compiled in, always convert standard send to sync send
> > - compiled in, use MCA parameter to determine whether to convert
> > standard -> sync
> >
> > And we can leave the default as "compiled out".
> >
> > Howzat?
> I don't understand, what the purpose of the middle state? It seems
> like
> a bad idea to me.

It's the difference between:

a. if (0) { ... convert ... } Modern compilers will remove this code
as part of dead-code removal.
b. if (1) { ... convert ... } Modern compilers will remove the "if
(1)" and always execute the code.
c. if (some_variable) { ... convert ...} An MCA parameter can load
some_variable with 0 or 1.

The point of b is for sysadmins (or individual developers) who want to
force there to *always* be correct MPI applications.

Jeff Squyres