[petsc-users] DMDA questions

[Matthew Knepley]

On Fri, Feb 28, 2014 at 1:16 PM, Xiangdong <epscodes at gmail.com> wrote:

> If I assembly the matrix with MatSetValuesStencil and use KspSetOpreators
> for Ksp, do I need to call KspSetDM first?
>

No


> What is the key difference or advantage of using KspSetComputeOperators
> against KspSetOperators?
>

With the later, you have to manage creating and preallocating the matrix.

   Matt


> Thanks you.
>
> Xiangdong
>
>
> On Tue, Feb 25, 2014 at 4:24 PM, Jed Brown <jed at jedbrown.org> wrote:
>
>> Xiangdong <epscodes at gmail.com> writes:
>> > I am not clear about this. In this example, where is the format
>> declaration
>> > (e.g.,mpiaij) of Mat jac? Why is this mat jac always distributed in
>> > a compatible way as the DM vectors?
>>
>> src/ksp/ksp/examples/tutorials/ex25.c calls KSPSetDM and sets functions
>> to assemble the matrices and right hand side.  Those objects are created
>> internally (you can use -dm_mat_type sbaij if you like) and the user
>> doesn't have to see them.
>>
>
>


-- 
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
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20140228/be12f6b0/attachment.html>