[petsc-users] help needed for -snes_mf_operator

[Matthew Knepley]

On Wed, Apr 25, 2012 at 2:19 PM, Dominik Szczerba <dominik at itis.ethz.ch>wrote:

> > Notice that there is no increase in the residual as is required. Notice
> also
> > that
> > there is no decrease. This must mean that the preconditioner is rank
> > deficient,
> > and I think it probably means that it is 0 since I find it hard to
> believe
> > that P x
> > produces no component in the b direction.
>
> Should this be the case, how would I get correct results for several
> benchmarks without using the option?


This is not what I said. Look closely at the above. I said the
preconditioner you give
back when using -snes_mf_operator is not right. This has nothing to do with
normal
operation.

   Matt


>
> Dominik
>



-- 
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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