VecView behaviour
Andreas Grassl
Andreas.Grassl at student.uibk.ac.at
Thu Jun 4 17:13:50 CDT 2009
Barry Smith schrieb:
>
> Run with GMRES, what happens?
Same behaviour...
>
> On Jun 4, 2009, at 11:07 AM, Andreas Grassl wrote:
>
>> Barry Smith schrieb:
>>>
>>> On Jun 3, 2009, at 5:29 PM, Andreas Grassl wrote:
>>>
>>>> Barry Smith schrieb:
>>>>>
>>>>> When properly running nn-cg (are you sure everything is symmetric?)
>>>>> should require 10-30 iterations (certainly for model problems)
>>>>
>>>> ok, this was the number I expected.
>>>>
>>>>>
>>>>>> nn-cg on 2 nodes 229 iterations, condition 6285
>>>>>> nn-cg on 4 nodes 331 iterations, condition 13312
>>>>>
>>>>> Are you sure that your operator has the null space of only constants?
>>>>
>>>> no, I didn't touch anything regarding the null space since I thought
>>>> it would be
>>>> done inside the NN-preconditioner. Does this mean I have to set up a
>>>> null space
>>>> of the size of the Schur complement system, i.e. the number of
>>>> interface DOF's?
>>>
>>> No, I don't think you need to do anything about the null space. The
>>> code in PETSc for NN is for (and only for) a null space of constants.
>>> BTW: with 2 or 4 subdomains they all touch the boundary and likely don't
>>> have a null space anyways.
>>>
>>> Run with -ksp_view and make sure the local solves are being done with LU
>>>
>>
>> I don't find the anomalies... setting local_ksp-rtol to 1e-8 doesn't
>> change anything
>>
>> the options passed are:
>>
>> -is_localD_ksp_type preonly
>> -is_localD_pc_factor_shift_positive_definite
>> -is_localD_pc_type lu
>> -is_localN_ksp_type preonly
>> -is_localN_pc_factor_shift_positive_definite
>> -is_localN_pc_type lu
>> -ksp_rtol 1e-8
>> -ksp_view
>> #-is_localD_ksp_view
>> #-is_localN_ksp_view
>> #-nn_coarse_ksp_view
>> # -pc_is_remove_nullspace_fixed this option doesn't produce any effect
>> -log_summary
>> -options_left
>>
>> and produce:
>>
>> -ksp_view:
>>
>> KSP Object:
>> type: cg
>> maximum iterations=10000
>> tolerances: relative=1e-08, absolute=1e-50, divergence=10000
>> left preconditioning
>> PC Object:
>> type: nn
>> linear system matrix = precond matrix:
>> Matrix Object:
>> type=is, rows=28632, cols=28632
>> Matrix Object:(is)
>> type=seqaij, rows=7537, cols=7537
>> total: nonzeros=359491, allocated nonzeros=602960
>> using I-node routines: found 4578 nodes, limit used is 5
>> Matrix Object:(is)
>> type=seqaij, rows=7515, cols=7515
>> total: nonzeros=349347, allocated nonzeros=601200
>> using I-node routines: found 5159 nodes, limit used is 5
>> Matrix Object:(is)
>> type=seqaij, rows=7533, cols=7533
>> total: nonzeros=357291, allocated nonzeros=602640
>> using I-node routines: found 4739 nodes, limit used is 5
>> Matrix Object:(is)
>> type=seqaij, rows=7360, cols=7360
>> total: nonzeros=364390, allocated nonzeros=588800
>> using I-node routines: found 3602 nodes, limit used is 5
>>
>> -is_local...:
>>
>> KSP Object:(is_localD_)
>> type: preonly
>> maximum iterations=10000, initial guess is zero
>> tolerances: relative=1e-05, absolute=1e-50, divergence=10000
>> left preconditioning
>> PC Object:(is_localD_)
>> type: lu
>> LU: out-of-place factorization
>> matrix ordering: nd
>> LU: tolerance for zero pivot 1e-12
>> LU: using Manteuffel shift
>> LU: factor fill ratio needed 4.73566
>> Factored matrix follows
>> Matrix Object:
>> type=seqaij, rows=6714, cols=6714
>> package used to perform factorization: petsc
>> total: nonzeros=1479078, allocated nonzeros=1479078
>> using I-node routines: found 2790 nodes, limit used is 5
>> linear system matrix = precond matrix:
>> Matrix Object:
>> type=seqaij, rows=6714, cols=6714
>> total: nonzeros=312328, allocated nonzeros=312328
>> using I-node routines: found 4664 nodes, limit used is 5
>>
>> KSP Object:(is_localN_)
>> type: preonly
>> maximum iterations=10000, initial guess is zero
>> tolerances: relative=1e-05, absolute=1e-50, divergence=10000
>> left preconditioning
>> PC Object:(is_localN_)
>> type: lu
>> LU: out-of-place factorization
>> matrix ordering: nd
>> LU: tolerance for zero pivot 1e-12
>> LU: using Manteuffel shift
>> LU: factor fill ratio needed 5.07571
>> Factored matrix follows
>> Matrix Object:
>> type=seqaij, rows=7537, cols=7537
>> package used to perform factorization: petsc
>> total: nonzeros=1824671, allocated nonzeros=1824671
>> using I-node routines: found 2939 nodes, limit used is 5
>> linear system matrix = precond matrix:
>> Matrix Object:(is)
>> type=seqaij, rows=7537, cols=7537
>> total: nonzeros=359491, allocated nonzeros=602960
>> using I-node routines: found 4578 nodes, limit used is 5
>>
>>
>> -nn_coarse_ksp_view:
>>
>> KSP Object:(nn_coarse_)
>> type: preonly
>> maximum iterations=10000, initial guess is zero
>> tolerances: relative=1e-05, absolute=1e-50, divergence=10000
>> left preconditioning
>> PC Object:(nn_coarse_)
>> type: redundant
>> Redundant preconditioner: First (color=0) of 4 PCs follows
>> KSP Object:(redundant_)
>> type: preonly
>> maximum iterations=10000, initial guess is zero
>> tolerances: relative=1e-05, absolute=1e-50, divergence=10000
>> left preconditioning
>> PC Object:(redundant_)
>> type: lu
>> LU: out-of-place factorization
>> matrix ordering: nd
>> LU: tolerance for zero pivot 1e-12
>> LU: factor fill ratio needed 1
>> Factored matrix follows
>> Matrix Object:
>> type=seqaij, rows=4, cols=4
>> package used to perform factorization: petsc
>> total: nonzeros=4, allocated nonzeros=4
>> not using I-node routines
>> linear system matrix = precond matrix:
>> Matrix Object:
>> type=seqaij, rows=4, cols=4
>> total: nonzeros=4, allocated nonzeros=4
>> not using I-node routines
>> linear system matrix = precond matrix:
>> Matrix Object:
>> type=mpiaij, rows=4, cols=4
>> total: nonzeros=4, allocated nonzeros=68
>> not using I-node (on process 0) routines
>>
>>
>> cheers,
>>
>> ando
>>
>> --
>> /"\ Grassl Andreas
>> \ / ASCII Ribbon Campaign Uni Innsbruck Institut f. Mathematik
>> X against HTML email Technikerstr. 13 Zi 709
>> / \ +43 (0)512 507 6091
>
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