[petsc-users] SAME_PRECONDITIONER vs. DIFFERENT_NONZERO_PATTERN

[Jed Brown]

On Wed, May 30, 2012 at 1:58 PM, John Fettig <john.fettig at gmail.com> wrote:

> I have a question about the difference between SAME_PRECONDITIONER and
> DIFFERENT_NONZERO_PATTERN.  If you solve multiple RHS's (with
> different initial guesses) but the matrix does not change, should you
> expect to get identical results with SAME_PRECONDITIONER and
> DIFFERENT_NONZERO_PATTERN?


Why are you even calling KSPSetOperators? Just call KSPSolve() for each
right hand side.


> I think it should be, but I'm finding that
> not to be the case with ML.
>

Are you sure the matrix hasn't changed? What kind of differences are you
observing?
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