[petsc-users] (Fast?) assembly of upper triangle and MatZeroRows

[Jed Brown]

On Mon, Aug 8, 2011 at 14:44, Barry Smith <bsmith at mcs.anl.gov> wrote:

> > How would you use this interface with SNES?
>
>    The user calls this as part  the FormJacobian()  (in the same way as if
> they explicitly remove those rows and columns (what Matt likes) in the
> matrix assembly.


But they need access to the right hand side at the same time. It seems too
fragile to reach into the SNES and modify the residual vector during
Jacobian evaluation.
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