What do you set on the sphere? If you impose a Dirichlet BC that makes it nonsingular
Mohammad On Feb 14, 2012 7:27 AM, "Jed Brown" <jedbrown at mcs.anl.gov> wrote: > On Tue, Feb 14, 2012 at 09:20, Thomas Witkowski < > thomas.witkowski at tu-dresden.de> wrote: > >> I discretize the Laplace operator (using finite element) on the unit >> square equipped with periodic boundary conditions on all four edges. Is it >> correct that the null space is still constant? I wounder, because when I >> run the same code on a sphere (so a 2D surface embedded in 3D), the >> resulting matrix is non-singular. I thought, that both cases should be >> somehow equal with respect to the null space? >> > > The continuum operators for both cases have a constant null space, so if > either is nonsingular in your finite element code, it's a discretization > problem. > -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20120214/8898efcb/attachment.htm>
