[petsc-users] MatAYPX for dense and sparse matrices

[Jed Brown]

On Mon, Mar 21, 2011 at 12:40, Alexander Grayver <agrayver at gfz-potsdam.de>wrote:

> One more question. I get matrix J out of MatMatMult operation and then I
> have to add L matrix up, wouldn't there be a conflict using
> MatAssemblyBegin/MatAssemblyEnd again? Generally, is it allowed to set new
> values into the matrix after MatAssemblyBegin/MatAssemblyEnd already has
> been done once?
>

Yes, you can assemble again. Just set the values, then call
MatAssembly{Begin,End}. It is not okay to set values, skip (re)assembling,
and call MatMult() or something.
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