[petsc-users] non-convergence for SNES ex5 and ex20

[Qian Zhu]

On Jun 22, 2011, at 10:26 AM, Jed Brown wrote:

> On Wed, Jun 22, 2011 at 16:58, Qian Zhu <qzhu at mcs.anl.gov> wrote:
> For ex5, par=xxx,  using "-ksp_type gmres -pc_type ilu" will make the solution converge while using "-ksp_type cg -pc_type jacobi" cannot (all ksp's and pc's are just randomly picked...they may not make sense).
> 
> boundary conditions are not symmetric in this example
>  
> What would this "xxx" value be? Or is there any input parameters I am missing out for these applications?
> 
> look at snes ex19 and use  -lidvelocity 100 -grashof 1e5 if you are looking for something that doesn't converge. Or try a Stokes problem.

Thanks for the reply, Jed. I worked on ex27 so I know setting certain values for the input parameters can make the case converge/non-converge...I am just wondering whether this is also true with ex5 and ex20 (We picked them for other interesting characteristics). Which examples are solving the Stokers problem?

Thanks a lot! 

Qian Zhu, Ph.D.
Mathematics and Computer Science Division
Argonne National Laboratory
9700 S.Cass Avenue
Argonne, IL 60439-4844
Phone: 630-252-0086

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