[petsc-users] query DMPlexCreateSection

[Matthew Knepley]

On Thu, Jan 2, 2014 at 4:11 AM, Dharmendar Reddy <dharmareddy84 at gmail.com>wrote:

> Hello,
>          I am trying to use DMPlexCreateSection from fortran. I was
> able to solve a Poisson equation earlier using DMPlex for handling
> mesh data.
>
> Now i need to solve a system of equations: (poisson + continuity equations)
>
> - div (grad phi) = (C + n)  --- (1)
>   div (J ) = 0  ---------------  (2)
>   J = n grad(phi)
> ( C is constant)
> Simulation domain is defined as, rectangular regions 1 and 2 shown below.
>
> -------------
> |     1        |
> -------------
> |               |
> |       2      |
> |               |
> --------------
>
> Now, equation 1 is defined in region 1 and 2
> and equation 2 is defined only for region 2.
>
> How do i setup the section  ? DMPlexCreateSection applies the given
> DOF layout  per cell to all cells in the mesh.
>
> I am not sure if all the function calls inside
> DMPlexCreateSectionIntial and DMPlexCreateSectionBCDof  are accessible
> from Fotran.
>

You don't want them anyway since they apply to the whole domain. The
control flow could be:

  DMPlexSetChart()
  <loop over region 1>
    DMPlexSetDof() and DMPlexSetFieldDof()
  <loop over region 2>
    DMPlexSetDof() and DMPlexSetFieldDof()
  <loop over BC>
    DMPlexSetConstraintDof() and DMPlexSetFieldConstraintDof()
  DMPlexSetUp()
  <loop over BC>
    DMPlexSetConstraintIndices() and DMPlexSetFieldConstraintIndices()

We could try and package some of this up if it looks generic.

  Thanks,

     Matt


> Thanks
> Reddy
>
> --
> -----------------------------------------------------
> Dharmendar Reddy Palle
>



-- 
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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