[petsc-users] Question about MatCreateSubMatrix

Matthew Knepley knepley at gmail.com
Thu Mar 29 15:10:40 CDT 2018

On Thu, Mar 29, 2018 at 3:28 PM, Manav Bhatia <bhatiamanav at gmail.com> wrote:

> Hi,
>   I have quick questions about MatCreateSubMatrix:
> — Once the sub matrix is created, do I need to keep the IS (isrow and
> iscol) in memory till this matrix is active, or can I destroy it
> immediately after the creation of the matrix and continue to use the matrix?

You can destroy it.

> — Is the assembly begin/end supposed to be called on the submatrix or the
> original full matrix? Is it a problem is I call this on both?

The SubMatrix is not a view. Its a fully independent matrix.

> — If I modify values in the sub matrix, would these be reflected in the
> original matrix after assembly begin/end, or do I need to do something else
> for that to happen?

No. Do you want something like this




> Thanks,
> Manav

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

https://www.cse.buffalo.edu/~knepley/ <http://www.caam.rice.edu/~mk51/>
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