[petsc-dev] CFLAGS and COPTFLAGS

[William Gropp]

If the MPI wrapper adds -O, its buggy.  The wrapper should only do what is necessary to get MPI to compile (header and library paths) and nothing else.  If MPICH does more, that is a bug (note that recent autoconf really, really wants to specify -g -O2 for gcc; that doesn't change the fact that it is wrong to do so).

Bill

William Gropp
Director, Parallel Computing Institute
Deputy Director for Research
Institute for Advanced Computing Applications and Technologies
Thomas M. Siebel Chair in Computer Science
University of Illinois Urbana-Champaign




On Jan 18, 2014, at 10:43 AM, Jed Brown wrote:

> Barry Smith <bsmith at mcs.anl.gov> writes:
>>   Do people really set some of the above and not set the -O%d one at the same time?
> 
> I don't know.  Sometimes the MPI wrapper adds the -O flag itself.  The
> user might know that and thus not bother adding it themselves.  I think
> it would be surprising for some special flags to cause such changes in
> behavior.  I don't have a strong opinion on this point, but I think we
> should do something better than we have now.

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