A different kind of lagged preconditioner

[Matthew Knepley]

On Mon, Mar 23, 2009 at 2:06 PM, Rafael Santos Coelho <
rafaelsantoscoelho at gmail.com> wrote:

> Barry,
>
> sorry if I'm coming off stubborn or something, but I think I'm not
> following your reasoning.
>
>  NO.
>>
>>  If you are using LU to construct a preconditioner then you ARE providing
>> the Jacobian explicitly (as a sparse) matrix.  Each time the preconditioner
>> is built this sparse matrix is factored.
>
>
> What do you mean by "providing the jacobian explicity (as a sparse)
> matrix"? I thought that there was no explicit jacobian matrix, but only a
> MATMFFD context.
>

If there is no matrix, what are you factoring?

   Matt


>
> Rafael
>
-- 
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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