[petsc-users] Monotonic convergence in FGMRES.

[Jed Brown]

On Tue, Dec 21, 2010 at 21:04, Barry Smith <bsmith at mcs.anl.gov> wrote:

> This is a sign that the preconditioner is seriously messed up and should
> not be used in its current form.  It can happen if the matrix is nearly
> singular and for example you use an incomplete factorization for a
> preconditioner that just screws up the scaling like totally. Run with
> -ksp_monitor_true_residual and you'll see that the solver is not really
> solving the problem even though it thinks it is converging fine.


FGMRES only does right preconditioning so it should be showing the true
residual.
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