[petsc-users] Efficient computation of A'*A

[Jed Brown]

On Wed, Jun 15, 2011 at 18:54, Alexander Grayver <agrayver at gfz-potsdam.de>wrote:

> I've got simple question.
> What is the most efficient way to compute B = A'*A using petsc?
> Matrix A is sparse MPIAIJ.
>

What are you going to do with B = A'*A?

The most efficient thing is MatCreateTranspose() which does no computation.

http://www.mcs.anl.gov/petsc/petsc-as/snapshots/petsc-current/docs/manualpages/Mat/MatCreateTranspose.html


If you need B assembled, then create a diagonal matrix and use MatPtAP()

http://www.mcs.anl.gov/petsc/petsc-as/snapshots/petsc-current/docs/manualpages/Mat/MatPtAP.html
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