New approach for external direct solvers in PETSc

[Barry Smith]

    We will most definitely make a release by December 1 2008. This  
means any
changes like this will have to be made pretty soon. Any changes will  
actually
have only a small effect on the user interface (but a bigger effect on  
PETSc's simplicity).

    Barry

On Aug 16, 2008, at 11:55 PM, Chen Shen wrote:

> Hi,
>
> May I know if this change will appear in petsc-devel soon? We are  
> trying to interface Petsc to a proprietary direct solver package. If  
> we should expect the change soon, we may consider push back the plan  
> a little bit. Thank you.
>
> regards,
> shenchen
>
> On Tue, Aug 12, 2008 at 12:40 AM, Barry Smith <bsmith at mcs.anl.gov>  
> wrote:
>
>   Mat in PETSc is actually a short hand notation for "Linear  
> transformation"
> http://en.wikipedia.org/wiki/Linear_transformation. Essentially the  
> only
> operation defined by a linear transformation is A*x. Matrices are  
> simply one
> way of representing finite dimensional linear transformations. So a
> Mat is suppose to ALWAYS provide a MatMult() everything else is  
> optional :-).
>
>  Now you can certainly say that we should have called linear  
> transformations
> in PETSc something like: LT or LinearTrans or many other things. We  
> chose
> Mat since almost everyone understands linear transformations as  
> matrices so
> we do not need to provide a high-falutin explanation of LT that  
> would simply
> alienate and scare most potential users. Everyone thinks they  
> understand
> Mat immediately.
>
>
>   Now back to the issue at hand. You had a very valid point in the  
> previous
> email: for a factored matrix if we define MatMult() as the  
> triangular solves
> then the factored matrix defines a linear transformation (whose  
> representation
> is not simply a two dimensional array, but is slightly more  
> complicated beast).
> So we could define a MATFACTOR as a new Mat object, like MatMFFD is
> a Mat object and then subclass the various packages factors  
> undernether
> it.
>
>   Barry
>
>
>
>
>
>
>
> On Aug 11, 2008, at 9:11 AM, Lisandro Dalcin wrote:
>
> On Fri, Aug 8, 2008 at 2:01 PM, Barry Smith <bsmith at mcs.anl.gov>  
> wrote:
>  This is just at hack to avoid so many changes in PETSc.
> MatMFFD is truly a matrix (it has matrix vector product).
>
> Well, I'm not so sure about that. Do it has MatSetValues() ?
>
>
>
>  Barry
>
> On Aug 8, 2008, at 8:23 AM, Lisandro Dalcin wrote:
>
> Barry, after thinking a bit more, I believe I've found an approach
> that is not so radical.
>
> Why not to follow the approach for MatMFFD? That is, introduce a new
> matrix type, instead of a brand new object type. Let me call this new
> matrix type MATFACTOR. This new matrix type contains a hidden
> PetscObject, and that object is filled with appropriate methods
> depending on the MatSolverPackage.
>
> This new way will not introduce a new object type in the user-level
> API. An I believe that we will still simplify the code. Now a MatSolve
> in a MATSEQAIJ matrix will fail just because it will not have the
> operation filled in the 'virtual table'. MATFACTOR will fill the
> MatXXXFactor{Symbolic/Numeric} options in the vtable, but it will not
> fill things like MatMult and MatSetValues. This way, we will not need
> any more to 'check' if a standard matrix type like SEQAIJ, MPIAIJ, etc
> are or are not factored (and perhaps we can handle dense matrices in a
> special way, just because inplace factorizations do really make
> sense). So the all the 'mat->factor' checks can finally go away!
>
> What do you think?
>
>
>
>
> On Thu, Aug 7, 2008 at 5:05 PM, Barry Smith <bsmith at mcs.anl.gov>  
> wrote:
>
> On Jul 25, 2008, at 5:47 PM, Lisandro Dalcin wrote:
>
> BTW, Have you ever considered the posibility of not using the 'Mat'
> class for factored matrices?? I believe that normal matrices and
> factored matrices share very few in common as to being instances of
> the same class. Looking at the source code in src/mat, there are many
> checks like 'if (mat-->factor)' or  'if (!mat->factor)' that seems to
> support my concern. What do you think?
>
> After a (tiny) bit more thought I think we really should make this
> change:
>
> pros
> 1) it will simplify the code a good amount hence less bugs
> 2) conceptually it makes sense
> cons
> 1) requires a large reorganization of the Mat code (will introduce  
> bugs)
> 2) requires the user to deal with one more PETSc object (MatFactor)
>  But since most users deal with SNES/KSP/PC most users will
>  never see this new object.
>
> The question is when/how to make this massive change. It is as big
> or bigger than the change I already made with MatGetFactor().
>
> Barry
>
>
>
>
>
> On Fri, Jul 25, 2008 at 7:02 PM, Barry Smith <bsmith at mcs.anl.gov>  
> wrote:
>
> petsc-dev users,
>
> I have finally completed my changes to PETSc for a new approach to
> accessing external direct solvers
> in PETSc like Spooles, MUMPS etc. I will be pushing it to petsc-dev
> sometime
> the middle of next week.
> If you are using the direct solvers you might consider cloning from
>
> http://petsc.cs.iit.edu/hg/petsc/petsc-dev-new-solvers  or
>
> ssh://petsc@petsc.cs.iit.edu//hg/petsc/petsc-dev-new-solvers
>
> and trying it out before then. Please report problem to
> petsc-maint at mcs.anl.gov as you hit them.
>
>
> Barry
>
> From the changes file
>
> The "parallel direct solver" matrix types like
> MATAIJSPOOLES are ALL gone. Now you use -pc_factor_mat_solver_package
> spooles etc or PCFactorSetMatSolverPackage() or if working directly
> with
> matrices, MatGetFactor(A,MATSPOOLES,...)
>
>
>
>
>
> --
> Lisandro Dalcín
> ---------------
> Centro Internacional de Métodos Computacionales en Ingeniería (CIMEC)
> Instituto de Desarrollo Tecnológico para la Industria Química (INTEC)
> Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET)
> PTLC - Güemes 3450, (3000) Santa Fe, Argentina
> Tel/Fax: +54-(0)342-451.1594
>
>
>
>
>
>
> --
> Lisandro Dalcín
> ---------------
> Centro Internacional de Métodos Computacionales en Ingeniería (CIMEC)
> Instituto de Desarrollo Tecnológico para la Industria Química (INTEC)
> Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET)
> PTLC - Güemes 3450, (3000) Santa Fe, Argentina
> Tel/Fax: +54-(0)342-451.1594
>
>
>
>
>
>
> -- 
> Lisandro Dalcín
> ---------------
> Centro Internacional de Métodos Computacionales en Ingeniería (CIMEC)
> Instituto de Desarrollo Tecnológico para la Industria Química (INTEC)
> Consejo Nacional de Investigaciones Científicas y Técnicas (CONICET)
> PTLC - Güemes 3450, (3000) Santa Fe, Argentina
> Tel/Fax: +54-(0)342-451.1594
>
>
>