[petsc-users] ILUTP

[Xiaoye S. Li]

The sequential SuperLU has ILUTP implementation, not in parallel versions.
PETSc already supports the option of using SuperLU.

In SuperLU distribution:
  EXAMPLE/zitersol.c : an example to use GMRES with ILUTP preconditioner
(returned from driver SRC/zgsisx.c)
  SRC/zgsitrf.c : the actual ILUTP factorization routine

Sherry Li



On Wed, Oct 30, 2013 at 8:48 AM, Matthew Knepley <knepley at gmail.com> wrote:

> On Wed, Oct 30, 2013 at 8:58 AM, Torquil Macdonald Sørensen <
> torquil at gmail.com> wrote:
>
>> Thanks Matthew!
>>
>> The problem I'm working on is the Dirac equation, in various number of
>> dimensions. I'm going to take a stab at multigrid preconditioning.
>>
>
> My limited knowledge of the Dirac Equation tells me that it is a
> relativistic wave equation, and thus hyperbolic, which is quite difficult
> for
> MG (but doable with a bunch of work). How do you have this formulated?
>
>   Thanks,
>
>      Matt
>
>
>> Best regards
>> Torquil Sørensen
>>
>>
>> On 27 October 2013 14:48, Matthew Knepley <knepley at gmail.com> wrote:
>>
>>> On Sat, Oct 26, 2013 at 3:05 PM, Torquil Macdonald Sørensen <
>>> torquil at gmail.com> wrote:
>>>
>>>> Hi!
>>>>
>>>> I have a linear problem Ax=b, with complex values, that is solved very
>>>> well using the ILUTP and GMRES implementations in GMM++. None of the other
>>>> preconditioners available in GMM++ would work (e.g. ILU and ILUT) for this
>>>> problem.
>>>>
>>>> Then I tried the same problem using ILU and GMRES in PETSc, with no
>>>> success, despite a lot of attempts at adjusting ILU settings. I always end
>>>> up with gigantic residual norm values. The same PETSc program works well
>>>> when I apply it to a different matrix A.
>>>>
>>>> I'm now suspecting that the ILU options cannot be set so as to obtain
>>>> ILUTP behaviour.
>>>>
>>>> What would be the recommended method to access an ILUTP preconditioner
>>>> from PETSc?
>>>>
>>>> According to the PETSc website, a preconditioner named ILUDT is
>>>> available by using the external package Hypre, but I had to deselect Hypre
>>>> during the PETSc build due to my use of complex numbers... So do you guys
>>>> think that I should transform everything to a real representation and try
>>>> Hypre/ILUDT?
>>>>
>>>
>>> I suggest you look for a different preconditioner. The fact that you
>>> have so much trouble reproducing the behavior shows
>>> you just how fragile the performance of ILU is. It may work for a
>>> certain size, but fail for larger or smaller problems, or slightly
>>> different parameters. What problem are you solving? Usually the best
>>> option is to consult the literature for preconditioners
>>> tailored to your problem, and then reproduce them.
>>>
>>>    Matt
>>>
>>>
>>>> Best regards
>>>> Torquil Sørensen
>>>>
>>>>
>>>
>>>
>>> --
>>> 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
>>>
>>
>>
>
>
> --
> 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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