[petsc-users] (no subject)

[Yingjie Wu]

Dear Petsc developer:
Hi,
I recently begin a new program, which is a two-dimensional nonlinear PDEs
problem, and solved by SNES.  However, there is an error. The log is :

Linear solve did not converge due to DIVERGED_PCSETUP_FAILED iterations 0
                 PCSETUP_FAILED due to FACTOR_NUMERIC_ZEROPIVOT
Nonlinear solve did not converge due to DIVERGED_LINEAR_SOLVE iterations 0
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=0
  total number of function evaluations=18903
  norm schedule ALWAYS
  Jacobian is built using finite differences one column at a time
  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: 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-05, absolute=1e-50, divergence=10000.
    left preconditioning
    using PRECONDITIONED norm type for convergence test
  PC Object: 1 MPI processes
    type: lu
      out-of-place factorization
      tolerance for zero pivot 2.22045e-14
      matrix ordering: nd
      factor fill ratio given 5., needed 20.7926
        Factored matrix follows:
          Mat Object: 1 MPI processes
            type: seqaij
            rows=18901, cols=18901
            package used to perform factorization: petsc
            total: nonzeros=3029644, allocated nonzeros=3029644
            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=18901, cols=18901
      total: nonzeros=145708, allocated nonzeros=341390
      total number of mallocs used during MatSetValues calls =16459
        not using I-node routines

I used "-snes_fd -pc_type lu" to test the program.
The error shows that there are some zero elements in the matrix. What might
cause this problem?

Thanks,
Yingjie
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