[petsc-users] Petsc ILU PC Change between 3.6.4 and 3.7.x?

[Gaetan Kenway]

Hi All

I'm in the process of updating a code that uses PETSc for solving linear
systems for an unstructured CFD code. As of recently, it was using an
ancient version (3.3). However, when I updated it up to 3.7.6 I ended up
running into issues with one of the KSP solves. The remainder of the code
is identical,
I've tracked the issue down to occurring between version 3.6.4 and version
3.7.0 . The same issue is present on the most recent version 3.7.6.

Specifically the issue is that on the second iteration, on the 3.7 version
the KSP kicks out with KSP converged reason of -11 or
KSP_DIVERGED_PCSETUP_FAILED
<http://www.mcs.anl.gov/petsc/petsc-current/docs/manualpages/KSP/KSP_DIVERGED_PCSETUP_FAILED.html#KSP_DIVERGED_PCSETUP_FAILED>
.
After that the two runs differ.  The KSPView for each of the two are given
below which are identical, up to small formatting changes. There is still
more I can track down, but I thought I would ask if someone knows what
might have changed between these two versions which could save me a lot of
time.

Thanks,
Gaetan

3.6 KSP View:
KSP Object: 8 MPI processes
  type: gmres
    GMRES: restart=3, using Classical (unmodified) Gram-Schmidt
Orthogonalization with no iterative refinement
    GMRES: happy breakdown tolerance 1e-30
  maximum iterations=3
  using preconditioner applied to right hand side for initial guess
  tolerances:  relative=1e-08, absolute=1e-20, divergence=1e+15
  left preconditioning
  using nonzero initial guess
  using PRECONDITIONED norm type for convergence test
PC Object: 8 MPI processes
  type: bjacobi
    block Jacobi: number of blocks = 8
    Local solve is same for all blocks, in the following KSP and PC objects:
  KSP Object:  (sub_)   1 MPI processes
    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:  (sub_)   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=46439, cols=46439
            package used to perform factorization: petsc
            total: nonzeros=502615, allocated nonzeros=502615
            total number of mallocs used during MatSetValues calls =0
              not using I-node routines
    linear system matrix = precond matrix:
    Mat Object:     1 MPI processes
      type: seqaij
      rows=46439, cols=46439
      total: nonzeros=502615, allocated nonzeros=504081
      total number of mallocs used during MatSetValues calls =0
        not using I-node routines
  linear system matrix = precond matrix:
  Mat Object:   8 MPI processes
    type: mpiaij
    rows=368656, cols=368656
    total: nonzeros=4.63682e+06, allocated nonzeros=4.64417e+06
    total number of mallocs used during MatSetValues calls =0
      not using I-node (on process 0) routines
<my output: reason, iterations, rtol, atol>
reason,its: 2 3 0.001 1e-20


Petsc 3.7 KSP View
KSP Object: 8 MPI processes
  type: gmres
    GMRES: restart=3, using Classical (unmodified) Gram-Schmidt
Orthogonalization with no iterative refinement
    GMRES: happy breakdown tolerance 1e-30
  maximum iterations=3
  using preconditioner applied to right hand side for initial guess
  tolerances:  relative=1e-08, absolute=1e-20, divergence=1e+15
  left preconditioning
  using nonzero initial guess
  using PRECONDITIONED norm type for convergence test
PC Object: 8 MPI processes
  type: bjacobi
    block Jacobi: number of blocks = 8
    Local solve is same for all blocks, in the following KSP and PC objects:
  KSP Object:  (sub_)   1 MPI processes
    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:  (sub_)   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=46439, cols=46439
            package used to perform factorization: petsc
            total: nonzeros=502615, allocated nonzeros=502615
            total number of mallocs used during MatSetValues calls =0
              not using I-node routines
    linear system matrix = precond matrix:
    Mat Object:     1 MPI processes
      type: seqaij
      rows=46439, cols=46439
      total: nonzeros=502615, allocated nonzeros=504081
      total number of mallocs used during MatSetValues calls =0
        not using I-node routines
  linear system matrix = precond matrix:
  Mat Object:   8 MPI processes
    type: mpiaij
    rows=368656, cols=368656
    total: nonzeros=4636822, allocated nonzeros=4644168
    total number of mallocs used during MatSetValues calls =0
      not using I-node (on process 0) routines
<my output: reason, iterations, rtol, atol>
reason,its: -11 0 0.001 1e-20
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