[petsc-users] Convergence trouble with SNES and CG

[David Knezevic]

On Mon, Feb 22, 2016 at 6:57 PM, Barry Smith <bsmith at mcs.anl.gov> wrote:

>
>   Add -ksp_converged_reason
>


That gives "DIVERGED_INDEFINITE_PC". The full output is below:


  105 KSP Residual norm 7.099534889984e-05
  106 KSP Residual norm 6.615351528474e-05
  107 KSP Residual norm 6.303646443688e-05
  Linear solve converged due to CONVERGED_RTOL iterations 107
  NL step  5, |residual|_2 = 1.996487e+01
    0 KSP Residual norm 5.844456247091e+00
    1 KSP Residual norm 1.308756943973e+00
    2 KSP Residual norm 7.545133187463e-01
    3 KSP Residual norm 1.346068942607e+00
  Linear solve did not converge due to DIVERGED_INDEFINITE_PC iterations 4
SNES Object: 1 MPI processes
  type: newtonls
  maximum iterations=50, maximum function evaluations=10000
  tolerances: relative=1e-08, absolute=1e-50, solution=1e-08
  total number of linear solver iterations=535
  total number of function evaluations=11
  norm schedule ALWAYS
  SNESLineSearch Object:   1 MPI processes
    type: bt
      interpolation: cubic
      alpha=1.000000e-04
    maxstep=1.000000e+08, minlambda=1.000000e-12
    tolerances: relative=1.000000e-08, absolute=1.000000e-15,
lambda=1.000000e-08
    maximum iterations=40
  KSP Object:   1 MPI processes
    type: cg
    maximum iterations=10000, initial guess is zero
    tolerances:  relative=1e-05, absolute=1e-50, divergence=10000
    left preconditioning
    using NATURAL norm type for convergence test
  PC Object:   1 MPI processes
    type: ilu
      ILU: out-of-place factorization
      0 levels of fill
      tolerance for zero pivot 2.22045e-14
      matrix ordering: natural
      factor fill ratio given 1, needed 1
        Factored matrix follows:
          Mat Object:           1 MPI processes
            type: seqaij
            rows=967608, cols=967608
            package used to perform factorization: petsc
            total: nonzeros=7.55539e+07, allocated nonzeros=7.55539e+07
            total number of mallocs used during MatSetValues calls =0
              using I-node routines: found 322536 nodes, limit used is 5
    linear system matrix = precond matrix:
    Mat Object:    ()     1 MPI processes
      type: seqaij
      rows=967608, cols=967608
      total: nonzeros=7.55539e+07, allocated nonzeros=7.55539e+07
      total number of mallocs used during MatSetValues calls =0
        using I-node routines: found 322536 nodes, limit used is 5
Number of nonlinear iterations: 5
Nonlinear solver convergence/divergence reason: DIVERGED_LINEAR_SOLVE
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