[EMAIL PROTECTED] wrote: >> >> [EMAIL PROTECTED] wrote: >>>> [EMAIL PROTECTED] wrote: >>>>>> [EMAIL PROTECTED] wrote: >>>>>>>> One or more new changesets pushed to the primary dolfin repository. >>>>>>>> A short summary of the last three changesets is included below. >>>>>>>> >>>>>>>> changeset: 4730:6548c25c33352492c9279c035509a139caab323b >>>>>>>> tag: tip >>>>>>>> user: "Garth N. Wells <[EMAIL PROTECTED]>" >>>>>>>> date: Tue Sep 09 13:08:58 2008 +0100 >>>>>>>> files: dolfin/fem/Assembler.cpp dolfin/pde/LinearPDE.cpp >>>>>>>> description: >>>>>>>> Revert to old assembly in LinearPDE due to bug in symmetric >>>>>>>> assembly. >>>>>>>> >>>>>>>> There is a problem with exterior facets in the symmetric assembly. >>>>>>>> The >>>>>>>> code needs to be broken up to make debugging easier. >>>>>>>> >>>>>>> Agree that it should be broken up. But it will take some effort. >>>>>>> Do you have an example where the bug is apparent ? >>>>>>> >>>>>> I was using a RT0 element (not one of the demos). It should be >>>>>> reproducible by adding a non-zero Dirichlet bc (given be a Function) >>>>>> to >>>>>> the mixed-poisson demo. >>>>>> >>>>>> I had a quick look, but I couldn't find the problem, so I thought it >>>>>> better to wait until the code is broken up. >>>>>> >>>>>> Garth >>>>>> >>>>> Strange, I see no reason for this not to work. >>>>> (since the code involving only cell integrals is pretty clean, but >>>>> ...) >>>>> >>>>> Anyway, I noticed that with my setup, CG is used. CG can not be used >>>>> in this case since the problem is not positive. Did you use CG ? >>>> No, I used an LU solver. I first noticed the problem when the LU >>>> solvers >>>> return a message that the system was singular. I only looked at the >>>> computation of the RHS vector which was zero when it shouldn't have >>>> been. >>> Ok, and I guess the system is singular unless you have a mix of >>> essential >>> and natural >>> bc. But the rhs should not be zero. >>> >> The essential bcs appear in the form for this problem, so the assembler >> shouldn't be doing anything extra for the bcs (bcs.size() = 0 in >> Asssembler.cpp). Makes the bug rather strange. >> >> Garth >> > > So the essential bc that you refer to is the essential bc for the > classical Poisson problem > which ends up as natural in the mixed formulation. So you have something > like: > > L = w*f*dx + w*g*ds >
Exactly. Garth > I'll have a look. > > (But as already said, I completely agree on breaking up) > > Kent > > > > > > > _______________________________________________ DOLFIN-dev mailing list [email protected] http://www.fenics.org/mailman/listinfo/dolfin-dev
