[petsc-users] question about contexts

[Dominik Szczerba]

It does not seem to work, unless I just miss some C/C++ idiom.
I was wrong, StiffnessMatrixMultiplication can not be static member,
else all the other non-static members are inaccessible.
So I am trying non-static, but can not pray PCShellSetApply work with
such a function, always get some syntax error.

Any hints are highly appreciated.

Dominik



On Fri, Sep 30, 2011 at 5:54 PM, Dominik Szczerba <dominik at itis.ethz.ch> wrote:
> Yes, I only have one instance of my solver class, if this is what you
> mean by a singleton.
> I did not mean to cast my context, I meant to avoid any contexts and
> just access the members. I so far use the context only to pass KSP,
> Mat and Vec objects around a few functions. I am asking, because I
> have not seen anyone doing it, while it appears natural to me. Also, I
> am doubting if #define __FUNCT__ "StiffnessMatrixMultiplication" will
> continue to work for static functions.
>
> Thanks,
> Dominik
>
> On Fri, Sep 30, 2011 at 4:44 PM, Jed Brown <jedbrown at mcs.anl.gov> wrote:
>> On Fri, Sep 30, 2011 at 09:34, Dominik Szczerba <dominik at itis.ethz.ch>
>> wrote:
>>>
>>> I am currently declaring functions outside my C++ solver class to be
>>> used by via MatShellSetOperation like:
>>>
>>> #undef __FUNCT__
>>> #define __FUNCT__ "StiffnessMatrixMultiplication"
>>> PetscErrorCode StiffnessMatrixMultiplication(Mat A, Vec x, Vec y)
>>> {
>>>        // ...
>>>        ierr = MatShellGetContext(A, (void**) &ctx);CHKERRQ(ierr);
>>>        Mat foo;
>>>        foo = ctx->foo;
>>>        // ...
>>> }
>>>
>>> and I set/get contexts to e.g. pass 'foo' around. Is it possible in
>>> Petsc / is it a good idea / to instead declare such functions as
>>> static class member functions and then use the class members directly
>>> without any contexts shuffled around?
>>
>> You have to go through the context unless your class is a singleton. Or do
>> you still mean casting the ctx to your class type and accessing members
>> through it (explicit "this")? That should work, if you prefer.
>