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Subject: Re: [OMPI users] Open MPI programs with autoconf/automake?
From: Raymond Wan (rwan_at_[hidden])
Date: 2008-11-10 23:22:56


Hi Jeff,

Jeff Squyres wrote:
> On Nov 10, 2008, at 6:41 AM, Jed Brown wrote:
>>> With #define's and compiler flags, I think that can be easily done --
>>> was wondering if this is something that developers using MPI do and
>>> whether AC/AM supports it.
>
> AC will allow you to #define whatever you want -- look at the
> documentation for AC_DEFINE and AC_DEFINE_UNQUOTED. You can also tell
> your configure script to accept various --with-<foo> and
> --enable-<foo> arguments; see the docs for AC_ARG_WITH and AC_ARG_ENABLE.

Thanks for this! I know "it's in the document", but I've been going
through it with much difficulty. Definitely complete, but hard to get
into and know what it is I need. So, some keywords to search for will
definitely help!

> If --with-mpi is not specified, the following will happen:
>
> 1. You don't set CC (and friends), so AC_PROG_CC will find the default
> compilers. Hence, your app will not be compiled and linked against
> the MPI libraries.
> 2. #define BUILDING_WITH_MPI to 0, so the code above will compile out
> the call to MPI_Send().
>
> Both of these are valid techniques -- use whichever suits your app the
> best.
>

I see; thank you for giving me this second option. I guess I'm more
attracted to this since it allows me to continue working with Open MPI.
As I am writing the system [now], I'll have to keep in mind to make it
modular so that parts can be #define'd in and out easily.

Thank you for your careful explanation!

Ray