[petsc-users] GMRES restart guidelines

[Barry Smith]

> On Aug 26, 2016, at 2:15 PM, Justin Chang <jychang48 at gmail.com> wrote:
> 
> Hi all,
> 
> When exactly would one need to modify the default restart value of 30 for GMRES? I have seen papers like this which suggest playing around with values between 1 and 30, but are there cases where people need to use large restart values like 50 or 100?

  Sure. It is not ideal because the work and memory requirements go up but if you have a problem where even after proper preconditioning there are say 50 "bad" eigenvalue/eigenvectors of the preconditioned operator then using a larger value is valid.

  Barry

> 
> 
> Thanks,
> Justin