[petsc-users] GAMG

[jeremy theler]

I will try these options in a couple of hours (I have to go out now). I
forgot to mention that the geometry has revolution symmetry around the z
axis (just the geometry, not the problem because it has a non-symmetric
temperature distribution).
I am solving with only one proc, there are approx 50k nodes so 150k dofs.
Thanks again.

On Fri, Oct 28, 2016, 11:07 Mark Adams <mfadams at lbl.gov> wrote:

> Also, try solving the problem with a one level iterative method and
> Chebyshev, like:
>
> -ksp_type chebyshev
> -pc_type jacobi
>
> It will take a long time to solve but I just want to see if it has the
> same error.
>
>
> On Fri, Oct 28, 2016 at 10:04 AM, Mark Adams <mfadams at lbl.gov> wrote:
>
> GAMG's eigen estimator worked but the values are very high.  You have very
> low number of equations per processor, is this a thin body? Are the
> elements badly stretched?
>
> Do this again with these parameters:
>
> -mg_levels_ksp_type chebyshev
> -mg_levels_esteig_ksp_type cg
> -mg_levels_esteig_ksp_max_it 10
> ​​
> -mg_levels_ksp_chebyshev_esteig 0,.1,0,1.05
> -gamg_est_ksp_type cg
>
>
> On Fri, Oct 28, 2016 at 9:48 AM, Jeremy Theler <jeremy at seamplex.com>
> wrote:
>
> On Fri, 2016-10-28 at 09:46 -0400, Mark Adams wrote:
> > Please run with -info and grep on GAMG.
> >
> [0] PCSetUp_GAMG(): level 0) N=120726, n data rows=3, n data cols=6,
> nnz/row (ave)=41, np=1
> [0] PCGAMGFilterGraph():         99.904% nnz after filtering, with
> threshold 0., 13.7468 nnz ave. (N=40242)
> [0] PCGAMGCoarsen_AGG(): Square Graph on level 1 of 1 to square
> [0] PCGAMGProlongator_AGG(): New grid 1894 nodes
> [0] PCGAMGOptProlongator_AGG(): Smooth P0: max eigen=5.726852e+00
> min=1.330683e-01 PC=jacobi
> [0] PCSetUp_GAMG(): 1) N=11364, n data cols=6, nnz/row (ave)=196, 1
> active pes
> [0] PCGAMGFilterGraph():         99.9839% nnz after filtering, with
> threshold 0., 32.7656 nnz ave. (N=1894)
> [0] PCGAMGProlongator_AGG(): New grid 155 nodes
> [0] PCGAMGOptProlongator_AGG(): Smooth P0: max eigen=1.011119e+01
> min=1.832878e-04 PC=jacobi
> [0] PCSetUp_GAMG(): 2) N=930, n data cols=6, nnz/row (ave)=196, 1 active
> pes
> [0] PCGAMGFilterGraph():         100.% nnz after filtering, with
> threshold 0., 32.7806 nnz ave. (N=155)
> [0] PCGAMGProlongator_AGG(): New grid 9 nodes
> [0] PCGAMGOptProlongator_AGG(): Smooth P0: max eigen=2.116373e+00
> min=6.337173e-03 PC=jacobi
> [0] PCSetUp_GAMG(): 3) N=54, n data cols=6, nnz/row (ave)=34, 1 active
> pes
> [0] PCGAMGFilterGraph():         100.% nnz after filtering, with
> threshold 0., 5.66667 nnz ave. (N=9)
> [0] PCGAMGProlongator_AGG(): New grid 2 nodes
> [0] PCGAMGOptProlongator_AGG(): Smooth P0: max eigen=1.984549e+00
> min=8.582767e-03 PC=jacobi
> [0] PCSetUp_GAMG(): 4) N=12, n data cols=6, nnz/row (ave)=12, 1 active
> pes
> [0] PCSetUp_GAMG(): 5 levels, grid complexity = 1.48586
> error: PETSc error 77-0 'Eigen estimator failed: DIVERGED_NANORINF at
> iteration 0'
> in /home/gtheler/libs/petsc-3.7.4/src/ksp/ksp/impls/cheby/cheby.c
> KSPSolve_Chebyshev:440
>
>
>
> >
> >
> >
> >
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