[petsc-users] ksppreonly question

[Matthew Knepley]

On Fri, Sep 21, 2012 at 5:13 PM, Shao-Ching Huang <huangsc at gmail.com> wrote:

> Thanks. A1 is part of the Laplacian operator discretized by finite
> volume method on non-Cartesian mesh.
>

That is not very specific. Can you be more specific?

  Matt


> On Fri, Sep 21, 2012 at 3:09 PM, Matthew Knepley <knepley at gmail.com>
> wrote:
> > On Fri, Sep 21, 2012 at 2:45 PM, Shao-Ching Huang <huangsc at gmail.com>
> wrote:
> >>
> >> Hi
> >>
> >> I am trying to write the procedure of a legacy code in PETSc (for
> >> comparison purposes). Instead of solving the system "Ax = b", the
> >> legacy code iterates on something like:
> >>
> >> A1*x(n+1) = b - A2*x(n)
> >>
> >> where A=A1+A2 and "n" is the iteration index. It seems to me that I
> >> need to use ksppreonly
> >>
> >> (
> http://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/KSP/KSPPREONLY.html
> ).
> >
> >
> > This kind of splitting is common. PETSc has Richardson, Jacobi, SOR that
> do
> > this. What
> > are the matrices A1 and A2?
> >
> >    Matt
> >
> >>
> >> My question is: how do I update the right-hand-side, b - A2*x(n),
> >> after every iteration using PETSc API?
> >>
> >> Thanks.
> >>
> >> Shao-Ching
> >
> >
> >
> >
> > --
> > 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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