On Fri, Nov 13, 2015 at 2:48 PM, Matthew Knepley <[email protected]> wrote:
> On Fri, Nov 13, 2015 at 12:28 PM, Jed Brown <[email protected]> wrote: > >> Matthew Knepley <[email protected]> writes: >> > Something very strange is happening here. CG should converge >> monotonically, >> > but above it does not. What could be happening? >> >> Are you use -ksp_norm_type natural? CG is not monotone in other norms. >> > > Yikes! I did not check that. Why do we have PRECONDITIONED as the default > for CG? > > The two norm of the residual (ie, natural, right?) is not monotone either in CG. > Matt > > Also, if boundary conditions are enforced using a nonsymmetric >> formulation (for example), then you can get lack of monotonicity with CG >> that may not be catastrophic. >> > > > > -- > What most experimenters take for granted before they begin their > experiments is infinitely more interesting than any results to which their > experiments lead. > -- Norbert Wiener >
