Dear Petsc developers: Hi, Recently I encounter an error message, but I don't know how to solve it. I solve a problem of a system of nonlinear equations in which the coefficients of the system vary with variables. The Args are: mpiexec -n 1 ./myprogram -snes_mf_operator -snes_view -snes_converged_reason -snes_monitor -ksp_converged_reason -ksp_monitor -ksp_rtol 0.1 -snes_rtol 1e-8 -snes_max_funcs 10000000000 -snes_max_it 10000 -pc_factor_levels 6 The log is : 0 SNES Function norm 2.818062118573e+07 0 KSP Residual norm 1.967792312615e+05 1 KSP Residual norm 3.423312208841e+03 Linear solve converged due to CONVERGED_RTOL iterations 1 1 SNES Function norm 2.818049788401e+07 0 KSP Residual norm 1.960830037415e+05 1 KSP Residual norm 3.458649556419e+03 Linear solve converged due to CONVERGED_RTOL iterations 1 Nonlinear solve did not converge due to DIVERGED_LINE_SEARCH iterations 1 SNES Object: 1 MPI processes type: newtonls maximum iterations=10000, maximum function evaluations=1410065408 tolerances: relative=1e-08, absolute=1e-50, solution=1e-08 total number of linear solver iterations=2 total number of function evaluations=27 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: 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=0.1, absolute=1e-50, divergence=10000. left preconditioning using PRECONDITIONED norm type for convergence test PC Object: 1 MPI processes type: ilu out-of-place factorization 6 levels of fill tolerance for zero pivot 2.22045e-14 matrix ordering: natural factor fill ratio given 1., needed 4.29616 Factored matrix follows: Mat Object: 1 MPI processes type: seqaij rows=11368, cols=11368 package used to perform factorization: petsc total: nonzeros=183764, allocated nonzeros=183764 total number of mallocs used during MatSetValues calls =0 not using I-node routines linear system matrix followed by preconditioner matrix: Mat Object: 1 MPI processes type: mffd rows=11368, cols=11368 Matrix-free approximation: err=1.49012e-08 (relative error in function evaluation) Using wp compute h routine Does not compute normU Mat Object: 1 MPI processes type: seqaij rows=11368, cols=11368 total: nonzeros=42774, allocated nonzeros=56840 total number of mallocs used during MatSetValues calls =0 not using I-node routines I don't know what causes Line_Search to diverge. The Ksp_rtol setting in the program is very small because I find that linear-step convergence is not good. My best wishes for Christmas, Yingjie