[petsc-dev] Reverse dependencies

[Jed Brown]

This patch seems to do two very unrelated things. More importantly, it
makes libpetscmat depend on libpetscksp, thus breaking single-library=0.
The register routine needs to be moved to src/ksp to fix this.

In principle, I'd be fine with putting it in KSPRegisterAll. Instead of
thinking of that routine as "register all implementations of KSP" (which it
never truly meant), I think of it as "register all implementations of
anything provided by the KSP package". The downside of that is that
MatCreate calls MatInitializePackage, but does not call
KSPInitializePackage, causing MatSetType(S,MATSCHURCOMPLEMENT) to fail when
!defined(PETSC_USE_DYNAMIC_LIBRARIES) and KSPInitializePackage() has not
been called.

Unfortunately, I there isn't a way short of static constructors to
initialize only those packages that are linked. With C++, we could have a
static constructor that registered itself. With GCC and related compilers,
we can use __attribute__((constructor)) to get a routine called before main
(it would add the existing XXInitializePackage() to a list that
PetscInitialize() would call later). Both of these options run code before
main which means we have to be especially careful that it never causes an
error because that is very confusing.

On systems that don't support constructors, I think the user will have to
call KSPInitializePackage themselves if they are going to MatSetType
MATSCHURCOMPLEMENT before KSPCreate. I think this particular combination is
extremely unlikely, but I have a similar issue with my new KSPPOLY (the
implementation needs SNES to solve a constrained minimization problem) and
that makes sense to use via -ksp_type poly when the user does not interact
with SNES at all.

changeset:   ec8eb69c0c42
user:        Barry Smith <bsmith at mcs.anl.gov>
date:        Thu Aug 23 08:03:00 2012 -0500
files:       conf/test include/petscksp.h src/ksp/ksp/utils/schurm.c
src/mat/interface/matregis.c
description:
added testexamples_opengl rule
changed MatCreateSchurComplement to use the MatCreate_SchurComplement()
paradigm
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