[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 >> The application of bcs on external is within the loop over all cells. >> Shouldn't it be within a loop over all boundary cells? > > In the present code I only run over each cell once. After the computations > of the various integrals is performed, the BC is enforced. > > > Kent > _______________________________________________ DOLFIN-dev mailing list [email protected] http://www.fenics.org/mailman/listinfo/dolfin-dev
