dolfin team mailing list archive

[Johan Hake <hake@xxxxxxxxx>]

On Tuesday 03 February 2009 10:06:22 Anders Logg wrote:
> On Tue, Feb 03, 2009 at 12:40:16AM -0700, Bartosz Sawicki wrote:
> > Hi all,
> >
> > Have any of you, some experience with posteriori error estimation in
> > Dolfin? I'm playing with adaptive refinement techniques, where proper
> > error estimation is essential.
> > I try to use form language with discontinous Lagrange elements to
> > describe error, but the results are somehow strange.
> > I found that in Unicorn there are some error estimation code, but I
> > can't find any application of it or any example? Is this code working?
> >
> > regrd.
> > BArtek
>
> What is currently missing is the ability to evaluate integrands over
> cells and facets and not adding the results. 

I might be saying something totally uncorrelated here but...

couldn't you just assemble them one by one, using a matrix with the same 
sparsitypattern? Then you could substract or do what ever you like with the 
matrices.

Johan

> This is a fairly 
> straightforward extension of our current assembly algorithms and it's
> partly there already (additional argument values to assemble_cells).
>
> In the meantime, it's possible to evaluate at least the cell
> contribution by multiplying with a DG test function. We do this all
> the time and it works fine.
>
> There will be much improved support for a posteriori error estimation
> in future versions, including automated generation of dual problems
> and error estimators as part of UFL, although I can't promise when.