[petsc-users] DMDA questions

[Xiangdong]

On Fri, Feb 28, 2014 at 4:21 PM, Matthew Knepley <knepley at gmail.com> wrote:

> 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.
>

If I use DMCreateMatrix and MatSetValuesStencil, I do not need to
preallocate the matrix.

Xiangdong




>
>    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/d7ce4be3/attachment.html>