[petsc-users] Getting access to matrix rows without and setting values simultaneously

Jed Brown jed at 59A2.org
Thu Jun 16 10:40:07 CDT 2011

On Thu, Jun 16, 2011 at 17:34, Matthew Knepley <knepley at gmail.com> wrote:

> Yes, you can do MF applications of A' A. You could just make a MatShell
> that called MatMult and MatMultTranspose.

MatShell is not necessary, just use MatCreateTranspose().


But I think Alexander is clear on that part.

> For modifying the matrix, MatGetRow() IF you are using an AIJ matrix,
> return a pointer directly to the values.

This is only for SeqAIJ.

Alexander, could you clarify where in the Gauss-Newton procedure you
outlined is the dense matrix on which you need to do the nonlinear row

Also, the matrix A'*A has a huge null space. What sort of regularization are
you using.
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