[petsc-dev] Integrating PFLOTRAN, PETSC & SAMRAI

[Jed Brown]

On Mon, Jun 6, 2011 at 23:23, Barry Smith <bsmith at mcs.anl.gov> wrote:

> They do need to because of SNESComputeFunction().
>

It might be worth incrementing it here redundantly.


>
> Since VecRestoreArray() increases the state one could argument that we
> should remove all the state increase calls in the Vec base classes and Mat
> and always rely on VecRestoreArray(). And hence require all other Vec
> implementations to manage the state completely themselves?
>

That would be logically consistent, but it's fragile so it would need a very
good test suite. Incrementing the state redundantly is not expensive.
Incrementing state when it has not been modified is expensive. If the user
computes a norm inside their FormResidual() evaluation, it can't be reused
if state is incremented outside. If it's pre-incremented, then
(hypothetically) a CFL check or constraint satisfaction computed in advance
by the nonlinear solver would not be available inside.

It's just a matter of how much norm-like stuff the user might reasonably be
expected to do in their FormResidual().
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