[petsc-users] pc_redistribute issue

[Mark Adams]

Well, that puts the reason after the iterations, which is progress.

Oh, I see the preconditioned norm goes down a lot, but the reported
residual that you would think is used for testing (see first post) does not
go down 12 digits.
This matrix is very ill conditioned. LU just gets about 7 digits.

Thanks,
Mark

Residual norms for redistribute_ solve.
    0 KSP preconditioned resid norm 3.988887683909e+16 true resid norm
6.646245659859e+06 ||r(i)||/||b|| 1.000000000000e+00
    1 KSP preconditioned resid norm 3.257912040767e+02 true resid norm
1.741027565497e-04 ||r(i)||/||b|| 2.619565472898e-11
  Linear redistribute_ solve converged due to CONVERGED_RTOL iterations 1
KSP Object: (redistribute_) 1 MPI process
  type: gmres
    restart=30, using Classical (unmodified) Gram-Schmidt Orthogonalization
with no iterative refinement
    happy breakdown tolerance 1e-30
  maximum iterations=10000, initial guess is zero
  tolerances:  relative=1e-12, absolute=1e-50, divergence=10000.
  left preconditioning
  using PRECONDITIONED norm type for convergence test
PC Object: (redistribute_) 1 MPI process
  type: bjacobi
    number of blocks = 1
    Local solver information for first block is in the following KSP and PC
objects on rank 0:
    Use -redistribute_ksp_view ::ascii_info_detail to display information
for all blocks
    KSP Object: (redistribute_sub_) 1 MPI process
      type: preonly
      maximum iterations=10000, initial guess is zero
      tolerances:  relative=1e-05, absolute=1e-50, divergence=10000.
      left preconditioning
      using NONE norm type for convergence test
    PC Object: (redistribute_sub_) 1 MPI process
      type: lu
        out-of-place factorization
        tolerance for zero pivot 2.22045e-14
        matrix ordering: external
        factor fill ratio given 0., needed 0.
          Factored matrix follows:
            Mat Object: (redistribute_sub_) 1 MPI process
              type: mumps
              rows=44378, cols=44378
              package used to perform factorization: mumps
              total: nonzeros=50309372, allocated nonzeros=50309372
                MUMPS run parameters:

On Sat, Jan 27, 2024 at 12:51 PM Matthew Knepley <knepley at gmail.com> wrote:

> Okay, so the tolerance is right. It must be using ||b|| instead of ||r0||.
> Run with
>
>   -redistribute_ksp_monitor_true_residual
>
> You might have to force r0.
>
>   Thanks,
>
>      Matt
>
> On Sat, Jan 27, 2024 at 11:44 AM Mark Adams <mfadams at lbl.gov> wrote:
>
>> KSP Object: (redistribute_) 1 MPI process
>>   type: gmres
>>     restart=30, using Classical (unmodified) Gram-Schmidt
>> Orthogonalization with no iterative refinement
>>     happy breakdown tolerance 1e-30
>>   maximum iterations=10000, initial guess is zero
>>
>> *  tolerances:  relative=1e-12, absolute=1e-50, divergence=10000.*  left
>> preconditioning
>>   using PRECONDITIONED norm type for convergence test
>> PC Object: (redistribute_) 1 MPI process
>>   type: bjacobi
>>     number of blocks = 1
>>     Local solver information for first block is in the following KSP and
>> PC objects on rank 0:
>>     Use -redistribute_ksp_view ::ascii_info_detail to display information
>> for all blocks
>>     KSP Object: (redistribute_sub_) 1 MPI process
>>       type: preonly
>>       maximum iterations=10000, initial guess is zero
>>       tolerances:  relative=1e-05, absolute=1e-50, divergence=10000.
>>       left preconditioning
>>       using NONE norm type for convergence test
>>     PC Object: (redistribute_sub_) 1 MPI process
>>       type: lu
>>         out-of-place factorization
>>         tolerance for zero pivot 2.22045e-14
>>
>> On Sat, Jan 27, 2024 at 10:24 AM Matthew Knepley <knepley at gmail.com>
>> wrote:
>>
>>> View the solver.
>>>
>>>   Matt
>>>
>>> On Sat, Jan 27, 2024 at 9:43 AM Mark Adams <mfadams at lbl.gov> wrote:
>>>
>>>> I am not getting ksp_rtol 1e-12 into pc_redistribute correctly?
>>>>
>>>>
>>>>
>>>> * Linear redistribute_ solve converged due to CONVERGED_RTOL iterations
>>>> 1  0 KSP Residual norm 2.182384017537e+02   1 KSP Residual norm
>>>> 1.889764161573e-04 *
>>>> Number of iterations =   1 N = 47628
>>>> Residual norm 8.65917e-07
>>>> #PETSc Option Table entries:
>>>> -f S.bin # (source: command line)
>>>> -ksp_monitor # (source: command line)
>>>> -ksp_type preonly # (source: command line)
>>>> -mat_block_size 36 # (source: command line)
>>>> -mat_view ascii::ascii_info # (source: command line)
>>>> -options_left # (source: command line)
>>>> -pc_type redistribute # (source: command line)
>>>> -redistribute_ksp_converged_reason # (source: command line)
>>>>
>>>> *-redistribute_ksp_rtol 1e-12 # (source: command line)*-redistribute_ksp_type
>>>> gmres # (source: command line)
>>>> -redistribute_pc_type bjacobi # (source: command line)
>>>> -redistribute_sub_pc_factor_mat_solver_type mumps # (source: command
>>>> line)
>>>> -redistribute_sub_pc_type lu # (source: command line)
>>>> #End of PETSc Option Table entries
>>>> *There are no unused options.*
>>>>
>>>
>>>
>>> --
>>> What most experimenters take for granted before they begin their
>>> experiments is infinitely more interesting than any results to which their
>>> experiments lead.
>>> -- Norbert Wiener
>>>
>>> https://www.cse.buffalo.edu/~knepley/
>>> <http://www.cse.buffalo.edu/~knepley/>
>>>
>>
>
> --
> What most experimenters take for granted before they begin their
> experiments is infinitely more interesting than any results to which their
> experiments lead.
> -- Norbert Wiener
>
> https://www.cse.buffalo.edu/~knepley/
> <http://www.cse.buffalo.edu/~knepley/>
>
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