On Wed, Apr 3, 2013 at 11:04 PM, Dharmendar Reddy
<dharmareddy84 at gmail.com>wrote:
> Hello,
> I see that in DMPlexComputeResidualFEM boundary conditions are
> applied using DMPlexProjectFunctionLocal. I was wondering why is there a
> loop over all local vertex Ids and a call to
> evaluation function on line 241 below. If i am not wrong, i can see that
> VecSetValuesSection is only to the points indicated as boundary points in
> DMPlexCreatSection. Should one call lines 235:242 only if v is constrained
> node ? Also, should the user provide functions for all components of all
> fields, is there a way to update add value of only the field that is
> constrained ?
>
> 234: for (v = vStart; v < vEnd; ++v) {235: PetscInt
> <http://www.mcs.anl.gov/petsc/petsc-dev/docs/manualpages/Sys/PetscInt.html#PetscInt>
> dof, off;
> 237: PetscSectionGetDof
> <http://www.mcs.anl.gov/petsc/petsc-dev/docs/manualpages/IS/PetscSectionGetDof.html#PetscSectionGetDof>(cSection,
> v, &dof);238: PetscSectionGetOffset
> <http://www.mcs.anl.gov/petsc/petsc-dev/docs/manualpages/IS/PetscSectionGetOffset.html#PetscSectionGetOffset>(cSection,
> v, &off);239: if (dof > dim) SETERRQ2
> <http://www.mcs.anl.gov/petsc/petsc-dev/docs/manualpages/Sys/SETERRQ2.html#SETERRQ2>(PetscObjectComm
>
> <http://www.mcs.anl.gov/petsc/petsc-dev/docs/manualpages/Sys/PetscObjectComm.html#PetscObjectComm>((PetscObject
>
> <http://www.mcs.anl.gov/petsc/petsc-dev/docs/manualpages/Sys/PetscObject.html#PetscObject>)dm),
> PETSC_ERR_ARG_WRONG, "Cannot have more coordinates %d then dimensions %d",
> dof, dim);240: for (d = 0; d < dof; ++d) coords[d] =
> PetscRealPart(cArray[off+d]);241: for (c = 0; c < numComp; ++c) values[c]
> = (*funcs[c])(coords);242: VecSetValuesSection
> <http://www.mcs.anl.gov/petsc/petsc-dev/docs/manualpages/Vec/VecSetValuesSection.html#VecSetValuesSection>(localX,
> section, v, values, mode);243: }
>
> ProjectFunction() just implements \int_\Omega v f(x). If you really don't
want to add a no-op function, I can
check for NULL, but I think that is slower in the inner loop.
Matt
> --
> -----------------------------------------------------
> Dharmendar Reddy Palle
> Graduate Student
> Microelectronics Research center,
> University of Texas at Austin,
> 10100 Burnet Road, Bldg. 160
> MER 2.608F, TX 78758-4445
> e-mail: dharmareddy84 at gmail.com
> Phone: +1-512-350-9082
> United States of America.
> Homepage: https://webspace.utexas.edu/~dpr342
>
--
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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