[dune-fem] parallel solver issue

[Radcliffe, Alastair]

Hi fellow Dune-femers,

I've come across an interesting issue with the non-convergence of the parallel solvers (istl or fem) for the (latest on the "stokes" branch) fem-howto example 04 when using Dirichlet boundary conditions on a dgf mesh i generated recently, see below.

dune-fem version 1.4, and version 2.3 for the dune core modules

Any feedback from someone who knows how the parallel solvers work would be gratefully received ...

Thanks,

Alastair


________________________________________
From: Dedner, Andreas
Sent: Friday, April 10, 2015 11:49 PM
To: Radcliffe, Alastair
Subject: Re: Fw: bug in alu or fem

Hi Alastair.
I can't figure out anything at the moment.
You should perhaps report the bug to the dune-fem mailinglist with that
dgf file.
Andreas


On 10/04/15 19:15, Radcliffe, Alastair wrote:
> Hi,
>
> 'it' was a non-convergence of the solver, and the fem solvers didn't work either i think ... and of course, there are very few dune preconditioners that work in parallel to try ...
>
> the only way i've found to get it to 'solve' is to set the required residual to something e+3 or so ... then at least you can get paraview output to check it has "ranked" (ie: divided) the geometry up nicely ...
>
> i was hoping howto example 04 would do as a "minimal working example" for debugging ... but is it an alu or a dune-fem bug, so i can post it on the correct bug list ?
>
> Ta,
>
> Alastair
>
> ps: see you monday?, tuesday?, wednesday ? ...
>
> ________________________________________
> From: Dedner, Andreas
> Sent: Friday, April 10, 2015 4:18 PM
> To: Radcliffe, Alastair
> Subject: Re: Fw: bug in alu or fem
>
> Hi Alastair.
> Yes I can conform it - whatever 'it' was in your case. You really have
> to learn to write
> meaningful and helpful error reports! In my case the program got stuck -
> but is that the
> same behaviour you saw? Also: what sort of tests did you do? For
> example, did you see if
> there is an endless loop in the solver (setting the verbosity flag to
> 1)? I did do that and the
> solver then printed "nan" for the residual. It starts off ok but then
> goes bad. Did you test a
> different solver, i.e., change the flag in Makefile.am to not use istl.
> Anything else you tried/
> Best
> Andreas
>
>
>
> On 08/04/15 12:18, Radcliffe, Alastair wrote:
>> mpiexec -np 2 main