On Fri, Jun 22, 2012 at 9:19 AM, Barry Smith <bsmith at mcs.anl.gov> wrote:
> CGNE is only for people who have A (which is square) and want to solve > the normal equations with CG using the preconditioner of A and its > transpose for the preconditioner. Basically it allows the user to avoid > computing A'A explicitly or making their own shell matrix. It is > definitely not a substitute for LSQR. What? Maybe you are saying the same thing, but CGNE is a general-purpose non-symmetric method. It works well when the singular values are much better behaved than eigenvalues. A unitary matrix is a classic example where CGNE converges in one iteration (unpreconditioned), but GMRES and CGS need N iterations. -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20120622/42b21a0d/attachment.html>
