# [petsc-users] (no subject)

Yingjie Wu yjwu16 at gmail.com
Fri Dec 7 09:03:44 CST 2018

```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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