On Mon, Mar 20, 2017 at 9:33 PM, Barry Smith <[email protected]> wrote:
> > > On Mar 20, 2017, at 6:07 PM, Daralagodu Dattatreya Jois, Sathwik Bharadw > <[email protected]> wrote: > > > > Hey all, > > > > I am using AIJ matrix to solve Laplace problem in finite element > framework. To apply Neumann boundary conditions I need to obtain values of > first and last few columns and subtract it with the corresponding right > hand side vector. I understand that MatGetColumnVector andMatGetValues are > not collective. Is there any other alternative petsc calls to achieve this > in parallel? > > Hmm, I think you mean non-zero Dirichlet boundary conditions. In that > case the recommended approach is calling MatZeroRows() or if you want to > preserve symmetry MatZeroRowsColumns(). There are also MatZeroRowsLocal() > and MatZeroRowsColumnsLocal() and a few other variants. > > Barry > If we zero out rows AND columns using MatZeroRowsColumns to preserve the symmetry, how we connect the non-zero boundary values with the interior solution? Fande, > > > > > > Thanks, > > Sathwik > >
