[petsc-dev] Suggestions for MatProductCreate()

[Matthew Knepley]

On Mon, Mar 23, 2020 at 5:12 PM Lisandro Dalcin <dalcinl at gmail.com> wrote:

>
>
> On Mon, 23 Mar 2020 at 17:57, hzhang at mcs.anl.gov <hzhang at mcs.anl.gov>
> wrote:
>
>> Lisandro:
>>
>>> MatProductSetFromOptions() is not really setting any options. It looks
>>> like the correct name for this API is MatProductSetUp(). In any case, it
>>> looks like both SetFromOptions() and SetUp() should be provided.
>>>
>>
>> Not all product and matrix types enable algorithmic options. For those
>> who do have options,
>> MatProductSetFromOptions_mattype_producttype() enables it.
>> See MatProductSetFromOptions_MPIAIJ_AB().
>>
>
> I have to insist, you should separate SetFromOptions() from SetUp(). For
> many types, SetFromOptions may be empty (you can even use a NULL pointer to
> handle these cases), but the rest of the code that does setup stuff (that
> is, preparing the data structures) should go SetUp() routines.
> This design pattern is used everywhere in PETSc. That's the proper way to
> do it, IMHO. This way is the one that gives maximum flexibility to power
> users/developers, because some times developers may want to configure
> objects with some parameters, and do a SetUp() without calling
> SetFromOptions() to prevent users to mess up with the parameters the
> developer carefully chose.
>

I agree here. We should not be using options in SetUp or setting up in
SetFromOptions() since it might not be called. I am tying to fix all this
in DM.

   Matt


> --
> Lisandro Dalcin
> ============
> Research Scientist
> Extreme Computing Research Center (ECRC)
> King Abdullah University of Science and Technology (KAUST)
> http://ecrc.kaust.edu.sa/
>


-- 
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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