[petsc-dev] XXXGetContext() in Fortran

[Satish Balay]

On Thu, 10 Nov 2011, Jed Brown wrote:

> On Wed, Nov 9, 2011 at 12:52, Barry Smith <bsmith at mcs.anl.gov> wrote:
> 
> > So what both Satish's and Ethan's email are saying is so long as you tell
> > the Fortran function the interface that shows the type being returned you
> > can "trick" the Fortran into thinking that data type is just coming from
> > another Fortran routine.
> >
> >   I think this should resolve your issues and everything should be
> > straightforward (no need for transfer function). Please let us know if this
> > is problematic.
> >
> 
> Thanks everyone. This works, and in hindsight, I should have looked at
> snes/examples/tutorials/ex5f90.F because it does this with
> SNESGetApplicationContext.
> 
> The unfortunate thing is that it appears that the user needs to write a
> custom interface for each such function in order to get the compiler to
> pass the pointer in a useful way. Is there a way for us to put some
> interface definitions into the library? An (ugly) alternative would be to
> provide some CPP macros that the user can use to get interface definitions
> without needing to hand-type it (they would pass in their user-defined
> type).
> 
> How can we manage multiple contexts with different types in the same file?
> It looks like perhaps I can put the interface definitions in different
> modules, which I can import at subroutine granularity. If I want to get the
> context out of two MatShells inside the same function, I would have to
> write helper functions so that they can import different interface
> definitions via different modules?

Perhaps we can use a generic interface definition - and then use
'transfer' function that Blaise refered to - in the user code.
[I havne't yet tried this with the prior example code...]

Satish