Ya, Lisandro, it's my mistake. It is indeed SPD. Thank you for your reminder!
Lisandro Dalcin wrote: > On 2/6/08, Ben Tay <zonexo at gmail.com> wrote: > Because my grid's are > >> non-uniform in both x,y directions. Shouldn't that result in a >> non-symmetric matrix? But I think it's still PD, positive definite. >> Correct me if I'm wrong. >> > > I believe you are wrong, unless you are using a non-standart spatial > discretization method. Is your Poisson equation using some additional > terms than the usual Laplace operator? For standard finite elements > and finite diferences, your matrix should be symmetric. Of course, > symmetry can be lost if you use the common trick of zeroing-out rows > for boundary conditions (using MatZeroRows and related). But even in > that case, I believe you can still use CG. > >
