VecView behaviour

[Andreas Grassl]

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

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