[petsc-users] about linear solver convergence

[Jed Brown]

On Tue, Oct 11, 2011 at 10:33, behzad baghapour
<behzad.baghapour at gmail.com>wrote:

> What is the difference between "unpreconditioned resid norm"


This is estimated implicitly using the Krylov iteration. It can become
inaccurate if the Krylov basis loses orthogonality (an issue of numerical
stability).


> and "true resid norm" in -ksp_monitor?


This builds the residual explicitly. It is expensive with some methods, e.g.
GMRES.
-------------- next part --------------
An HTML attachment was scrubbed...
URL: <http://lists.mcs.anl.gov/pipermail/petsc-users/attachments/20111011/b1230a5f/attachment.htm>