[petsc-dev] CFLAGS and COPTFLAGS

[Matthew Knepley]

On Sun, Jan 19, 2014 at 7:13 PM, Barry Smith <bsmith at mcs.anl.gov> wrote:

>
> On Jan 19, 2014, at 6:23 PM, Satish Balay <balay at mcs.anl.gov> wrote:
>
> > On Sun, 19 Jan 2014, Jed Brown wrote:
> >
> >> Barry Smith <bsmith at mcs.anl.gov> writes:
> >>
> >>>   Nope because in my previous assignment I asked Satish to check for
> >>>   -O stuff in compiler wrappers as well as CFLAGS.
> >>
> >> So if a user builds with MPICH, they'll get different optimization
> >> options than building with Open MPI, simply because MPICH includes -O2
> >> in the wrapper?
> >>
> >>>> and some compilers have funny names for
> >>>> optimization flags.
> >>>
> >>>   This is a small possibility because normally there is a -Od as well
> >>>   as the funny named other stuff. If we come upon another funny name
> >>>   that replaces -Od we can incorporate that as well.
> >>
> >> I'm just not wild about being in the business of classifying which
> >> options are related to optimization.
> >
> > Perhaps swapping the order from '$CFLAGS $COPTFLAGS' to '$COPTFLAGS
> > $CFLAGS' will suffice.
>
>    No, this needs to be done right. Turn off PETSc setting optimization
> flags if mpicc or CFLAGS attempts to set them.
>

I agree with Jed that this is problematic. We will end up fixing false
positives with this, only it will not
be a user error anymore (using CFLAGS instead of COPTFLAGS as indicated in
the docs), it will be
our error, and it will waste our time looking for it.

   Matt


>    Barry
>
> >
> > Satish
>
>


-- 
What most experimenters take for granted before they begin their
experiments is infinitely more interesting than any results to which their
experiments lead.
-- Norbert Wiener
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