[petsc-dev] Question About Petsc ILU

[Matthew Knepley]

On Thu, Dec 29, 2011 at 11:01 AM, Dave Nystrom <dnystrom1 at comcast.net>wrote:

> I have recently added the capability to have a separate preconditioning
> matrix in the petsc interface for the code I am working with.  I have two
> types of preconditioning matrices that I have questions about.  One is
> tridiagonal and the other is 7 diagonals.  In both cases, the the diagonals
> are all lexically adjacent.  Or phrased differently, the tridiagonal matrix
> has a bandwidth of 3 and the 7 diagonal matrix has a bandwidth of 7 and so
> they are compact or dense band systems.
>
> I was wondering what petsc ilu will do for preconditioning matrices like
> these.  Will it produce an exact lu factorization or a nearly exact
> factorization?  I'm interested in the answer to this question because I am
> thinking I might be able to run this preconditioner on the gpu using the
> txpetscgpu package.
>

If you are running ILU(0), it has exactly the same nonzero pattern. The
convergence is unpredictably. I would consult Yousef Saad's book for
further information.

   Matt


> Thanks,
>
> Dave
>



-- 
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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