[petsc-dev] OpenMP compiler options

[Jed Brown]

On Tue, May 29, 2012 at 10:56 AM, Satish Balay <balay at mcs.anl.gov> wrote:

> Perhaps the 'empty' flag check should be at the begining of the list..
>

No, because most compilers ignore the pragmas when no options are given. I
do not know of any portable way, short of running code, to determine
whether a compiler used the OpenMP pragmas or ignored them.


>
> [we do have other places in configure where we fix the order in which
> flags are checked - due to similar conflicts between compilers]
>
> Satish
>
> On Tue, 29 May 2012, Jed Brown wrote:
>
> > The OpenMP flags do not definitively identify that OpenMP is used. In
> > particular, IBM XL interprets Cray's option "-h omp" as being equivalent
> to
> > "-soname omp", then silently ignores the Open MP pragmas. We can perhaps
> > "fix" this instance by moving -qsmp up in the list, but we may eventually
> > need to move it to compilerOptions.py.
> >
> >   def configureLibrary(self):
> >     ''' Checks for -fopenmp compiler flag'''
> >     ''' Needs to check if OpenMP actually exists and works '''
> >     self.setCompilers.pushLanguage('C')
> >     #
> >     for flag in ["-fopenmp", # Gnu
> >                  "-h omp",   # Cray
> >                  "-mp",      # Portland Group
> >                  "-Qopenmp", # Intel windows
> >                  "-openmp",  # Intel
> >                  " ",        # Empty, if compiler automatically accepts
> > openmp
> >                  "-xopenmp", # Sun
> >                  "+Oopenmp", # HP
> >                  "-qsmp",    # IBM XL C/c++
> >                  "/openmp"   # Microsoft Visual Studio
> >                  ]:
> >       if self.setCompilers.checkCompilerFlag(flag):
> >         ompflag = flag
> >         break
> >
>
>
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