[Trilinos-Users] AztecOO restarted gmres

Heroux, Michael A maherou at sandia.gov
Fri Jan 29 15:13:32 EST 2016


If I understand your question correction, we don't have a way to directly control the number of restarts.  A restart occurs after AZ_option[AZ_kspace] iterations.  The number of restarts is a function of this parameter and the number of iteration you require in order to reach convergence.  For example, if you set AZ_option[AZ_kspace] = 30 and took 100 iterations to reach convergence, you would restart 3 times (after 30, 60 and 90 iterations).

Does this make sense?


From: Trilinos-Users <trilinos-users-bounces at trilinos.org<mailto:trilinos-users-bounces at trilinos.org>> on behalf of Danielle Catherine Maddix <dcmaddix at stanford.edu<mailto:dcmaddix at stanford.edu>>
Date: Friday, January 29, 2016 at 11:12 AM
To: Trilinos Users <trilinos-users at trilinos.org<mailto:trilinos-users at trilinos.org>>
Subject: [EXTERNAL] [Trilinos-Users] AztecOO restarted gmres


I am solving a non-symmetric indefinite PDE problem arising from PDEs. When use gmres_condnum, it encouraged me to increase the dimension of the Krylov space. So I increased it from the default 30 to 250 using the kspace AZ_option. I am also seeing better results using MGS rather than CGS. I was wondering if there was a way to also specify the number of restarts that we want or if that is done internally when the maximum number of iterations is specified.


Danielle Maddix
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