[petsc-dev] configure: generating guesses from liblist and includes

[Matthew Knepley]

On Thu, May 16, 2013 at 1:51 PM, Jed Brown <jedbrown at mcs.anl.gov> wrote:

> Satish Balay <balay at mcs.anl.gov> writes:
>
> > On Thu, 16 May 2013, Jed Brown wrote:
> >
> >> Matthew Knepley <knepley at gmail.com> writes:
> >>
> >> > I don't think this makes sense. A certain pair of library and include
> >> > makes sense. Decoupling these invites all sorts of mismatches which
> >> > would be hard to track down. I do not see what is wrong with the
> >> > strategy above?
> >>
> >> It causes confusing error conditions and in almost all cases, the same
> >> includes are used for all library guesses.
> >>
> >
> > Even for just the libraries I think we needed:
> > try (liba) if all true (test1,test2,test3) then accept (liba)
> > else try (libb) if all true (test1,test2,test3) then   accept (libb)
> >
> > hence the current code. Perhaps we need multiple semantics for
> > different situations.
>
> The problem that after finding a _library_ that works, then finding that
> the includes do not work, and we go on a tangent trying lots of
> different libs with that same broken include.  The include does not
> depend on the library so I think it should be tested independently.
>

I think the assumption that it is a tangent is incorrect. That is not how we
install packages. We install everything at once, and if installed correctly,
both tests should pass. If not, its not usable, and we look for another
installation. This is exactly what we are doing.

   Matt


> Note that if multiple includes need to be tried, the current approach
> requires
>
>   num_include_alternatives * num_lib_alternatives
>
> but it could be tested in only
>
>   num_include_alternatives + num_lib_alternatives
>
> Use of multiple includes is rare now, so I don't know if this would
> significantly affect speed.
>



-- 
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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