[petsc-users] ksppreonly question

[Shao-Ching Huang]

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


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