dolfin team mailing list archive

[Anders Logg <logg@xxxxxxxxx>]

On Sat, Jul 12, 2008 at 09:51:13PM +0100, Garth N. Wells wrote:
> 
> 
> Anders Logg wrote:
> > On Thu, Jul 03, 2008 at 06:07:08PM +0100, Garth N. Wells wrote:
> >>
> >> Kent-Andre Mardal wrote:
> >>> On to., 2008-07-03 at 08:03 +0100, Garth N. Wells wrote:
> >>>> DOLFIN wrote:
> >>>>> One or more new changesets pushed to the primary dolfin repository.
> >>>>> A short summary of the last three changesets is included below.
> >>>>>
> >>>>> changeset:   4374:6e1db926186ebfe9d9316b729a7d5747be3c5115
> >>>>> tag:         tip
> >>>>> parent:      4373:8f4accd9eb039d0d13412e8d871e7f1bfce896b8
> >>>>> parent:      4372:3abbccc877d3bb358c76ef36dbbe252155b88183
> >>>>> user:        Kent-Andre Mardal <kent-and@xxxxxxxxx>
> >>>>> date:        Wed Jul 02 16:02:17 2008 +0200
> >>>>> files:       dolfin/fem/Assembler.cpp dolfin/fem/DirichletBC.cpp site-packages/dolfin/assemble.py
> >>>>> description:
> >>>>> merge
> >>>>>
> >>>>>
> >>>>> changeset:   4373:8f4accd9eb039d0d13412e8d871e7f1bfce896b8
> >>>>> parent:      4369:b272b94b43ae789e2c72c90f6a027ce9fb89f6fc
> >>>>> user:        Kent-Andre Mardal <kent-and@xxxxxxxxx>
> >>>>> date:        Wed Jul 02 16:01:09 2008 +0200
> >>>>> files:       demo/pde/sym-dirichlet-bc/demo.py dolfin/fem/Assembler.cpp dolfin/fem/Assembler.h dolfin/fem/DirichletBC.cpp dolfin/fem/DirichletBC.h dolfin/fem/assemble.cpp dolfin/fem/assemble.h dolfin/la/AssemblyMatrix.cpp dolfin/la/AssemblyMatrix.h dolfin/la/EpetraMatrix.cpp dolfin/la/EpetraMatrix.h dolfin/la/EpetraVector.cpp dolfin/la/EpetraVector.h dolfin/la/GenericMatrix.h dolfin/la/GenericTensor.h dolfin/la/GenericVector.h dolfin/la/Matrix.h dolfin/la/PETScMatrix.cpp dolfin/la/PETScMatrix.h dolfin/la/PETScVector.cpp dolfin/la/PETScVector.h dolfin/la/Scalar.h dolfin/la/Vector.h dolfin/la/uBlasMatrix.h dolfin/la/uBlasVector.cpp dolfin/la/uBlasVector.h dolfin/swig/dolfin_fem_pre.i dolfin/swig/dolfin_headers.i site-packages/dolfin/assemble.py
> >>>>> description:
> >>>>> implemented symmetric handling of boundary conditions
> >>>>>
> >>>> Great.
> >>>>
> >>>> I looked at the demo but could see how to specify the method for 
> >>>> applying boundary conditions. Could you write a short description on how 
> >>>> to use it and it compares in terms of performance?
> >>>>
> >>>> Garth
> >>>>
> >>> Can you explain to me what the different methods do ? I assume you refer
> >>> to the topological, geometric, pointwise switch in computeBC (which
> >>> is used). 
> >>>
> >> I haven't looked at it in detail for some time, so I have to defer to 
> >> Anders and Kristian for a good explanation.
> > 
> > We have implemented 3 different strategies for locating the dofs for
> > which strong boundary conditions should be enforced:
> > 
> 
> I guess none of these strategies will work for P0 elements?
> 
> Garth

True, unless one uses the pointwise option and specifies the points as
the midpoints of the cells on the boundary.

I guess the proper way to specify boundary conditions for P0 elements
is weakly (using the same jump terms as for interior facets) as we've
done before.

-- 
Anders

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