[petsc-users] How Efficiently copy matrices

[Jed Brown]

On Sat, Oct 1, 2011 at 02:33, behzad baghapour
<behzad.baghapour at gmail.com>wrote:

> I want to copy some elements of a calculated matrix (A) into another matrix
> (B) with DIFFERENT_NONZERO_PATTERN.
>

Which "some elements"?


> How could I efficiently do this?
> Is this should be done after or before matrix assembly of (A)?
>

You can only copy after assembling A.


> Then, what is the sparse pattern of the matrix (A) after assembling and how
> is the correct access into its elements?
>

You probably want MatGetSubMatrix().
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