On Jun 22, 2012, at 4:11 PM, Jed Brown wrote: > 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.
Maybe you should add this to the KSPCGNE manual page. Without the "What?" :-) Barry
