[petsc-users] Interpreting ksp_view

[Barry Smith]

  Aldo,

    This is a bug. The allocated number was not multipled by the block size squared. Because of the this the compute unneeded number was garbage. We fixed this a while ago in petsc-dev (yes it should have been fixed as a patch for 3.1 but that didn't happen.)


    Barry


On Jun 30, 2011, at 8:17 AM, Aldo Bonfiglioli wrote:

> Dear all,
> I have a doubt concerning the interpretation of the output from -vec_view.
> I am using ILU(k) on a BAIJ matrix; the run is uni-processor.
>> KSP Object:
>>  type: gmres
>>    GMRES: restart=30, using Classical (unmodified) Gram-Schmidt Orthogonalization with no iterative refinement
>>    GMRES: happy breakdown tolerance 1e-30
>>  maximum iterations=10000, initial guess is zero
>>  tolerances:  relative=1e-05, absolute=1e-50, divergence=1e+10
>>  left preconditioning
>>  using PRECONDITIONED norm type for convergence test
>> PC Object:
>>  type: ilu
>>    ILU: out-of-place factorization
>>    ILU: Reusing fill from past factorization
>>    ILU: Reusing reordering from past factorization
>>    1 level of fill
>>    tolerance for zero pivot 1e-12
>>    using diagonal shift to prevent zero pivot
>>    matrix ordering: natural
>>    factor fill ratio given 1.30284, needed 1.30284
>>      Factored matrix follows:
>>        Matrix Object:
>>          type=seqbaij, rows=52995, cols=52995
>>          package used to perform factorization: petsc
>>          total: nonzeros=2398825, allocated nonzeros=95953
>>              block size is 5
>> [0] PetscCommDuplicate():   returning tag 1073741814
>>  linear system matrix = precond matrix:
>>  Matrix Object:
>>    type=seqbaij, rows=52995, cols=52995
>>    total: nonzeros=1841225, allocated nonzeros=73649
>>        block size is 5
> I have set the fill ratio and this is aknowledged.
> I do NOT understand why the nof allocated nonzeros does NOT match
> the nonzeros; this applies to both the A matrix and its ILU(k) preconditioner
> the ratio allocated nonzeros/nonzeros = 25 = blocksize^2 in both cases.
> Is there a bs*bs factor missing or am I misinterpreting the output?
> If a look at the MatInfo structure of the preconditioner
>> info =            1   25.000000000000000
>> info =            2   95953.000000000000
>> info =            3   2398825.0000000000
>> info =            4  -2302872.0000000000
>> info =            5   19576580.000000000
>> info =            6   0.0000000000000000
>> info =            7   0.0000000000000000
>> info =            8   1.3028418580021452
>> info =            9   1.3028418580021452
>> info =           10   0.0000000000000000
> a negative number of nz_unneeded seems to indicate that not enough memory has been provided.
> on the other hand, the -info option seems to confirm that the linear system matrix had been correctly pre-allocated
>> [0] MatAssemblyEnd_SeqBAIJ(): Matrix size: 52995 X 52995, block size 5; storage space: 0 unneeded, 1841225 used
>> [0] MatAssemblyEnd_SeqBAIJ(): Number of mallocs during MatSetValues is 0
> Thanks,
> Aldo
> 
>