VecView behaviour

[Andreas Grassl]

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
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>> / \                               +43 (0)512 507 6091
> 

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