http://petsc.cs.iit.edu/petsc/petsc-dev/rev/90ce2a6ecab0
On Fri, Jun 22, 2012 at 1:45 PM, Barry Smith <bsmith at mcs.anl.gov> wrote: > > 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 > > > -------------- next part -------------- An HTML attachment was scrubbed... URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20120622/a718e27a/attachment.html>
