On Aug 20, 2008, at 2:18 AM, Kent-Andre Mardal wrote: > On ti., 2008-08-19 at 14:59 -0500, Catherine Micek wrote: >> Hi, >> >> I have been looking at demo3.py in the dolfin demos in "sandbox/la/ >> trilinos/", which solves the Stokes system using preconditioners and >> an iterative solver. I can follow the code until it gets to applying >> the boundary conditions: >> >> # apply bc >> for bc in bcs: >> bc.apply(A00, b0, a00) >> bc.zero(A01, a00) >> >> Why do you apply the second command as "bc.zero(A01, a00)?" I would >> have guessed something more like "bc.zero(A01, a01)." Perhaps the >> better question is more general: how do the bc.apply and bc.zero >> commands work? >> >> Thanks! >> Katy > > bc.apply(A00, b0, a00) > will set the Dirichlet boundary conditions by seting > the part of A00 on the boundary to the identity and put > the boundary conditions in b0. > > bc.zero(A01, a00) will zero out the part on the boundary. > > Together these to commands create an identity matrix for > the part on the boundary for the block matrix.
Ok, this helps -- thanks! > > Kent > > > _______________________________________________ DOLFIN-dev mailing list [email protected] http://www.fenics.org/mailman/listinfo/dolfin-dev
