[petsc-users] DIVERGED_PCSETUP_FAILED

[Michele Rosso]

Hi,

I encountered the following error while solving a symmetric positive
defined system:

Linear solve did not converge due to DIVERGED_PCSETUP_FAILED iterations
0
               PCSETUP_FAILED due to SUBPC_ERROR 

This error appears only if I use the  optimized version of both petsc
and my code ( compiler: gfortran, flags: -O3 ).
It is weird since I am solving  a time-dependent problem and everything,
i.e. results and convergence rate, are as expected until the above error
shows up. If I run both petsc and my code in debug mode, everything goes
smooth till the end of the simulation.
However, if I reduce the ksp_rtol, even the debug run fails, after
running as expected for a while, because of a
KSP_DIVERGED_INDEFINITE_PC . 
The options I am using are:

-ksp_type        cg
-ksp_norm_type   unpreconditioned
-ksp_rtol        1e-8
-ksp_lag_norm
-ksp_initial_guess_nonzero  yes
-pc_type mg
-pc_mg_galerkin
-pc_mg_levels 4
-mg_levels_ksp_type richardson
-mg_coarse_ksp_constant_null_space
-mg_coarse_pc_type lu
-mg_coarse_pc_factor_mat_solver_package superlu_dist
-options_left

I attached a copy of ksp_view. I am currently using petsc-master (last
updated yesterday).
I would appreciate any suggestion on this matter.

Thanks,
Michele







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KSP Object: 1 MPI processes
  type: cg
  maximum iterations=10000
  tolerances:  relative=1e-08, absolute=1e-50, divergence=10000.
  left preconditioning
  using nonzero initial guess
  using UNPRECONDITIONED norm type for convergence test
PC Object: 1 MPI processes
  type: mg
    MG: type is MULTIPLICATIVE, levels=4 cycles=v
      Cycles per PCApply=1
      Using Galerkin computed coarse grid matrices
  Coarse grid solver -- level -------------------------------
    KSP Object:    (mg_coarse_)     1 MPI processes
      type: preonly
      maximum iterations=1, initial guess is zero
      tolerances:  relative=1e-05, absolute=1e-50, divergence=10000.
      left preconditioning
      using NONE norm type for convergence test
    PC Object:    (mg_coarse_)     1 MPI processes
      type: lu
        LU: out-of-place factorization
        tolerance for zero pivot 2.22045e-14
        using diagonal shift on blocks to prevent zero pivot [INBLOCKS]
        matrix ordering: nd
        factor fill ratio given 0., needed 0.
          Factored matrix follows:
            Mat Object:             1 MPI processes
              type: seqaij
              rows=16, cols=16
              package used to perform factorization: superlu_dist
              total: nonzeros=0, allocated nonzeros=0
              total number of mallocs used during MatSetValues calls =0
                SuperLU_DIST run parameters:
                  Process grid nprow 1 x npcol 1 
                  Equilibrate matrix TRUE 
                  Matrix input mode 0 
                  Replace tiny pivots FALSE 
                  Use iterative refinement FALSE 
                  Processors in row 1 col partition 1 
                  Row permutation LargeDiag 
                  Column permutation METIS_AT_PLUS_A
                  Parallel symbolic factorization FALSE 
                  Repeated factorization SamePattern
      linear system matrix = precond matrix:
      Mat Object:       1 MPI processes
        type: seqaij
        rows=16, cols=16
        total: nonzeros=72, allocated nonzeros=72
        total number of mallocs used during MatSetValues calls =0
          not using I-node routines
  Down solver (pre-smoother) on level 1 -------------------------------
    KSP Object:    (mg_levels_1_)     1 MPI processes
      type: richardson
        Richardson: damping factor=1.
      maximum iterations=2
      tolerances:  relative=1e-05, absolute=1e-50, divergence=10000.
      left preconditioning
      using nonzero initial guess
      using NONE norm type for convergence test
    PC Object:    (mg_levels_1_)     1 MPI processes
      type: sor
        SOR: type = local_symmetric, iterations = 1, local iterations = 1, omega = 1.
      linear system matrix = precond matrix:
      Mat Object:       1 MPI processes
        type: seqaij
        rows=64, cols=64
        total: nonzeros=304, allocated nonzeros=304
        total number of mallocs used during MatSetValues calls =0
          not using I-node routines
  Up solver (post-smoother) same as down solver (pre-smoother)
  Down solver (pre-smoother) on level 2 -------------------------------
    KSP Object:    (mg_levels_2_)     1 MPI processes
      type: richardson
        Richardson: damping factor=1.
      maximum iterations=2
      tolerances:  relative=1e-05, absolute=1e-50, divergence=10000.
      left preconditioning
      using nonzero initial guess
      using NONE norm type for convergence test
    PC Object:    (mg_levels_2_)     1 MPI processes
      type: sor
        SOR: type = local_symmetric, iterations = 1, local iterations = 1, omega = 1.
      linear system matrix = precond matrix:
      Mat Object:       1 MPI processes
        type: seqaij
        rows=256, cols=256
        total: nonzeros=1248, allocated nonzeros=1248
        total number of mallocs used during MatSetValues calls =0
          not using I-node routines
  Up solver (post-smoother) same as down solver (pre-smoother)
  Down solver (pre-smoother) on level 3 -------------------------------
    KSP Object:    (mg_levels_3_)     1 MPI processes
      type: richardson
        Richardson: damping factor=1.
      maximum iterations=2
      tolerances:  relative=1e-05, absolute=1e-50, divergence=10000.
      left preconditioning
      using nonzero initial guess
      using NONE norm type for convergence test
    PC Object:    (mg_levels_3_)     1 MPI processes
      type: sor
        SOR: type = local_symmetric, iterations = 1, local iterations = 1, omega = 1.
      linear system matrix = precond matrix:
      Mat Object:       1 MPI processes
        type: seqaij
        rows=1024, cols=1024
        total: nonzeros=5056, allocated nonzeros=5056
        total number of mallocs used during MatSetValues calls =0
          has attached null space
          not using I-node routines
  Up solver (post-smoother) same as down solver (pre-smoother)
  linear system matrix = precond matrix:
  Mat Object:   1 MPI processes
    type: seqaij
    rows=1024, cols=1024
    total: nonzeros=5056, allocated nonzeros=5056
    total number of mallocs used during MatSetValues calls =0
      has attached null space
      not using I-node routines