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Re: Trust Region problem

On 3/17/07, Gong Ding <gdiso@xxxxxxxx> wrote: 
Hi all,
   I use PETSC's nonelinear solver to do
emiconductor simulation. I found a strange problem
with trust region solvers. It usually works well
if LU method is used for inner linear solver. But
when krylov method i.e. GMRES, is employed, it
often stops due to pnorm is small, but still
remains large error of function norm. How to solve
this problem? LU method is much slower than i.e.
GMRES.


This sounds like GMRES is not actually converging (you can check this
using -ksp_monitor). You need a more powerful preconditioner, which
unfortunately usually depends a lot on the problem.

 Matt

G.D.
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