[firedrake] parallel weirdness

[Colin Cotter]

Hi Lawrence,
   Why does that term change the Krylov space? It's either added in ures,
or in that line.
Cjc
On 19 Nov 2014 17:23, "Lawrence Mitchell" <lawrence.mitchell at imperial.ac.uk>
wrote:

>
> On 19 Nov 2014, at 13:01, Hiroe Yamazaki <h.yamazaki at imperial.ac.uk>
> wrote:
>
> > Hi Lawrence,
> >
> > I updated the files with the exact settings I see the problem, so
> > could you run test_linear.py again with the current HEAD of the branch
> > "periodic_parallel" (267de84)? With this setting I got results that
> > looked different at t = 600*dt in serial and parallel. I've attached
> > the picture for your reference (left: serial, right: parallel(2
> > cores), serial run gives a symmetric result but parallel run results
> > in slightly asymmetric).
>
> Thanks, I see the problem.  I note that if I dial the solver tolerances up
> to 1e-10, then the problem appears to go away, but other than that I've got
> no idea.  I note that by moving this one term, you'll change the subspaces
> the Krylov solves explore.  If I monitor the convergence of the U solver, I
> see that the true residual is reduced less fast than the preconditioned
> residual, so is the problem that you somehow haven't killed the errors well
> enough?  Does this give any useful clues?
>
> Cheers,
>
> Lawrence
>
> _______________________________________________
> firedrake mailing list
> firedrake at imperial.ac.uk
> https://mailman.ic.ac.uk/mailman/listinfo/firedrake
>
>
-------------- next part --------------
HTML attachment scrubbed and removed