[Trilinos-Users] [EXTERNAL] AztecOO convergence
Salinger, Andrew
agsalin at sandia.gov
Mon Jun 24 13:54:03 MDT 2013
Bui,
I would suggest setting "Size of Krylov Space" = 1000.
This stagnation can occur after GMRES restarts.
If your user-defined preconditioner involves some iterative
solves or finite-difference perturbations, flexible GMRES can
also help. For this I would suggest the Belos BlockGMRES solver
that has a "Flexible GMRES" option.
Andy
From: Hoang Giang Bui <hgbk2008 at gmail.com<mailto:hgbk2008 at gmail.com>>
Date: Monday, June 24, 2013 12:02 PM
To: "trilinos-users at software.sandia.gov<mailto:trilinos-users at software.sandia.gov>" <trilinos-users at software.sandia.gov<mailto:trilinos-users at software.sandia.gov>>
Subject: [EXTERNAL] [Trilinos-Users] AztecOO convergence
Hi
When using AztecOO with user defined preconditioner. I obtained convergence behaviour like this:
*******************************************************
***** Problem: Epetra::CrsMatrix
***** Preconditioned GMRES solution
***** N4Teko22BlockLowerTriInverseOpE
***** No scaling
*******************************************************
iter: 0 residual = 1.000000e+00
iter: 100 residual = 1.698526e-03
iter: 200 residual = 3.441675e-04
iter: 300 residual = 4.356401e-05
iter: 400 residual = 3.333877e-05
iter: 500 residual = 1.901319e-05
iter: 600 residual = 1.574073e-05
iter: 700 residual = 1.438600e-05
iter: 800 residual = 1.372764e-05
iter: 900 residual = 1.351302e-05
iter: 1000 residual = 1.335775e-05 ***************************************************************
Warning: maximum number of iterations exceeded without convergence
Solver: gmres
number of iterations: 1000
Recursive residual = 3.6551e-08
The convergence rate at iteration > 200 is very slow. In this case, what should I do to improve the convergence rate of Gmres?
BR
Bui
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