[petsc-dev] Error checking on input only vectors

[Matthew Knepley]

On Tue, Jul 16, 2013 at 9:15 AM, Karl Rupp <rupp at mcs.anl.gov> wrote:

> Hey,
>
>      As an extra error checking on user code we could save the Vec state
>> of read only input Vecs and check it on exit of the routine to insure the
>> user has not changed the Vec. This could be done in PCApply_Shell(),
>> functions provided to SNES and TS etc.
>>
>
> we could do that, but I think this would slow the debug build down by
> quite a substantial amount (VecGetArrayRead() is used quite a lot
> internally as well), resulting in users to go with optimized builds during
> the development phase more often. Also, since VecGetArrayRead() returns a
> pointer to const, a user needs to cast away the const in order to
> manipulate entries, which already serves as an indication of doing
> something evil.
>

I think Barry is only suggesting we save the state integer.

   Matt


> What about a second debug level instead, something like
> 'PETSC_DEBUG_EXTRA', which enables additional, more expensive checks like
> the one you suggested? We could do similar valgrind-like checks for
> matrices, etc. there.
>
> Best regards,
> Karli
>
>
>
>> On Jul 16, 2013, at 8:08 AM, Rémi Lacroix <remi.lacroix at inria.fr> wrote:
>>
>>  Hello,
>>>
>>> I'm currently developing a preconditioner using PETSc. I have a small
>>> question about the PCApply function.
>>>
>>> Is it safe to destroy the content of the input vector x while applying
>>> the preconditioner or should I make a copy of it and work on that?
>>>
>>> Best regards,
>>>
>>> --
>>> Rémi Lacroix
>>> Équipe ALPINES
>>> Inria Paris-Rocquencourt / Laboratoire Jacques Louis Lions, UPMC
>>>
>>>
>>
>


-- 
What most experimenters take for granted before they begin their
experiments is infinitely more interesting than any results to which their
experiments lead.
-- Norbert Wiener
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