New approach for external direct solvers in PETSc

[Lisandro Dalcin]

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