[petsc-users] GAMG

[Mark Adams]

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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