Yes, you are right, I am trying to solve Oseen equation. I tried using preconditioner PCILU(1) which works well. But for PCILU(0) it did not work, as well as PCBJACOBI. I have tried to insert zero on the diagonal, but it still does not work.
In your opinion, what is the best parallel solver and preconditioner for the Oseen equation ? Thanks for your reply. Liang On 8/12/07, Barry Smith <bsmith at mcs.anl.gov> wrote: > > > It is not really the BiCGstab Krylov solver that it complaining; > it is the default ILU or block Jacobi with ILU on the blocks that is > complaining. > > You first need to make sure you insert 0 entries on the all the diagonal > entries that are 0. BUT given the structure of your matrix you may want > to think about solvers that specifically handle that type of matrix. > > Barry > > Stokes type solvers? > > > On Mon, 13 Aug 2007, Zhu Liang wrote: > > > By the way, the block of my matrix is like : > > > > U , a > > A^T , 0 > > > > > > > > ---------- Forwarded message ---------- > > From: Zhu Liang <liangcanada at gmail.com> > > Date: Aug 13, 2007 5:46 AM > > Subject: How can I use BICGStab on a matrix with zero entries on the > > diagonal > > To: petsc-users at mcs.anl.gov > > > > > > Dear petsc-users > > > > When I try to solve a linear equation Ax=b with BicgStab preconditioner, > I > > got > > an error "Matrix is missing diagonal number". That is because I have > zeros > > on > > the diagonal of the matrix. > > > > I am wondering if there is some simple method to avoid that? > > > > Best, > > Liang > > > > -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20070812/5d12bd3a/attachment.htm>
