[petsc-dev] PetscOptionsGetViewer() problems with multiple usage on the same object but different options databases

[Matthew Knepley]

On Sun, Jan 22, 2023 at 1:06 PM Barry Smith <bsmith at petsc.dev> wrote:

>
>   That makes incrementally adding new options to an existing object
> difficult, since each call to setFromOptions() screws up previous calls.
>
> We already have
>
> -ksp_monitor_cancel
> -ksp_converged_reason_view_cancel
>

Let me address it another way. If I understand correctly, what happens
currently is that at each ViewFromOptions() call, the database is inspected
and if a *_view is found, then the view is executed. So when you replace
the database, if this option is not found then nothing happens. This seems
to satisfy a kind of options locality. If instead we make some options
sticky, like -ksp_view, so that once given they never expire, this would
make the code exceedingly hard to reason about, especially if options are
set deep inside something, before a user is knowingly doing things. This
does not sound like the right model to me.

   Matt


> On Jan 22, 2023, at 12:45 PM, Matthew Knepley <knepley at gmail.com> wrote:
>
> On Sat, Jan 21, 2023 at 4:34 PM Barry Smith <bsmith at petsc.dev> wrote:
>
>>
>>   If I run KSPSetFromOptions() on an options database that contains
>> -ksp_view and then push another options database that does not contain
>> -ksp_view and call KSPSetFromOptions() again it undoes the previous setting
>> of that viewer.  So -ksp_view is not used.
>>
>>   I think this is the wrong model, it should not turn off the previously
>> set view just because it is not being set in the new call, since it was
>> previously set in the KSP. I fear some PETSc function will need another
>> argument to properly handle this; like another flag to
>> PetscOptionsGetViewer().
>>
>>   Note this is for much more than KSP.
>>
>>  Thoughts?
>>
>
> I think it must get rid of it. Otherwise, it would stay forever since
> there would be no way to get rid of it.
>
>   Matt
>
>
> --
> 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
>
> https://www.cse.buffalo.edu/~knepley/
> <http://www.cse.buffalo.edu/~knepley/>
>
>
>

-- 
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

https://www.cse.buffalo.edu/~knepley/ <http://www.cse.buffalo.edu/~knepley/>
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