[CMake] History and ideas behind FindMPI.cmake?

[Bartlett, Roscoe A]

Brad,

Thanks for the clarifications.

Note that MPI is unique in that it specifics how main(...) must be written and how to run programs on the command-line.  I can't think of any other library that does this (except perhaps other message passing standards).

- Ross


> -----Original Message-----
> From: Brad King [mailto:brad.king at kitware.com] 
> Sent: Tuesday, January 13, 2009 11:22 AM
> To: Bartlett, Roscoe A
> Cc: alin.elena at qub.ac.uk; cmake at cmake.org
> Subject: Re: [CMake] History and ideas behind FindMPI.cmake?
> 
> Alin M Elena wrote:
> > Do you really need an module for MPI?
> > 
> > All you need is to set the normal shell variables for 
> compilers to the 
> > MPI wrappers.
> > You need both mpi and non-mpi binaries just use different 
> build folders.
> 
> Alin is correct.  If the project works with an all-MPI build 
> you can just specify mpicc as the compiler (and similarly for 
> C++).  If anything in CMake prevents this from working we can 
> address the specific issue.
> The FindMPI module is useful for mixed projects that want 
> some MPI and some non-MPI binaries in the same tree.
> 
> AFAIK the MPI compiler wrappers are provided to help 
> non-software people (who may not understand ABIs, library 
> search paths, etc.) use MPI.  If every library took this 
> approach it would be impossible to use more than one library. 
>  Imagine if zlib required one to use zlibcc to link to it.
>  There is nothing wrong with using MPI libraries directly so 
> long as the proper compiler flags are found.  Teaching 
> FindMPI how to do this for all MPI distributions may take 
> some work but is not a wrong approach.
> 
> The current FindMPI module is one of the oldest find-modules in CMake.
> It has mostly been updated minimally as necessary for the 
> needs of folks willing to contribute their changes back to 
> us.  No one has taken the time to contribute a thorough treatment.
> 
> -Brad
> 
>