[petsc-dev] PetscFEM routines missing user data arguments

[Matthew Knepley]

On Thu, Nov 14, 2013 at 8:14 PM, Geoffrey Irving <irving at naml.us> wrote:

> On Thu, Nov 14, 2013 at 6:03 PM, Matthew Knepley <knepley at gmail.com>
> wrote:
> > On Thu, Nov 14, 2013 at 7:43 PM, Geoffrey Irving <irving at naml.us> wrote:
> >>
> >> It doesn't look like there's currently a way to pass user data down to
> >> the various fields in PetscFEM.  Can I add an extra argument to each
> >> function, or is that part of the API going to change in a way that
> >> would obviate the extra argument?
> >
> >
> > That is by design. Here is the rationale. I want to be able to use CUDA
> or OpenCL
> > to evaluate these low-level FEM integration routines, so you can't pass
> in arbitrary context.
> >
> > I really don't think we should need arbitrary information at the lowest
> level integration.
> > Right now you can pass in information using auxiliary fields. How would
> you use
> > other stuff?
>
> Well, you're probably not going to like application 1, which is
> passing around PyObject*'s so I can write little FEM explorations in
> numpy.  Is the field support the right thing to do for constant
> fields, or integer valued constant fields?


I should explain further. Here is the hierarchy:

  SNESComputeFunction (global)
  --> SNESComputeFunction_DMLocal (l2g)
    --> DMPlexComputeResidualFEM (local)
      --> PetscFEIntegrateResidual (chunk of cells)
        --> kernel (batch of cells)

I can be talked into a context all the way down to the kernel, which only
integrates a few cells
(like 32), but I would think that what you would do is write another
PetscFE that calls Python
(I have one for the CPU and one for OpenCL), and it has a context.

   Matt


>
> Geoffrey
>



-- 
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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