[petsc-users] Any changes in ML usage between 3.1-p8 -> 3.3-p6?

[Jozsef Bakosi]

On 04.17.2013 10:26, Jozsef Bakosi wrote:
> On 04.05.2013 08:34, Jozsef Bakosi wrote:
> > Hi folks,
> > 
> > In switching from 3.1-p8 to 3.3-p6, keeping the same ML ml-6.2.tar.gz, I get
> > indefinite preconditioner with the newer PETSc version. Has there been anything
> > substantial changed around how PCs are handled, e.g. in the defaults?
> > 
> > I know this request is pretty general, I would just like to know where to start
> > looking, where changes in PETSc might be clobbering the (supposedly same)
> > behavior of ML.
> > 
> 
> Alright, here is a little more information about what we see. Running the same
> setup/solve using ML (using the same ML and application source code) and
> switching from PETSc 3.1-p8 to 3.3-p6 appears to work differently, in some
> cases, resulting in divergence compared to the old version.
> 
> I attach the output from KSPView() called after KSPSetup() for the 3.1-p8
> (old.out) and for the 3.3-p6 (new.out), both running on 4 MPI ranks.
> 
> A diff reveals some notable differences:
> 
>   * using (PRECONDITIONED -> NONE) norm type for convergence test
> 
>   * (using -> not using) I-node routines
> 
>   * tolerance for zero pivot (1e-12 -> 2.22045e-14) for PPE_mg_levels_[12]_sub_
>     (stayed the same for PPE_mg_coarse_redundant_)
> 
> So we are wondering what might have changed in the PETSc defaults around how
> PCs, in particular ML, is used.
> 
> Thanks, and please let me know if I can give you more information,
> 
> Thanks,
> Jozsef


Another piece of info: The error we get is indefinite preconditioner.
Interestingly the same setup produces an OK preconditioner using 1,2,3, and 5
ranks -- indefinite only on 4.

ps: Please CC me as I'm not on the email list.

Thanks,
J