Dear Petsc developer: Hi, Thank you very much for your previous reply .
I recently wrote an example of neutron diffusion, which shows that the nonlinear residuals are gradually decreasing, but the program terminates in the tenth step of the nonlinear step.The program output information is as follows. -snes_fd -pc_type lu -snes_view -snes_converged_reason -snes_monitor_cancel -ksp_converged_reason -ksp_monitor_true_residual iter = 0, SNES Function norm 0.999045 0 KSP preconditioned resid norm 1.143042621777e+02 true resid norm 9.990445435144e-01 ||r(i)||/||b|| 1.000000000000e+00 1 KSP preconditioned resid norm 2.250033129078e-12 true resid norm 3.772661181818e-14 ||r(i)||/||b|| 3.776269242757e-14 Linear solve converged due to CONVERGED_RTOL iterations 1 iter = 1, SNES Function norm 0.863398 0 KSP preconditioned resid norm 3.176569252473e+00 true resid norm 8.633978674995e-01 ||r(i)||/||b|| 1.000000000000e+00 1 KSP preconditioned resid norm 7.360979829512e-14 true resid norm 1.835881897914e-14 ||r(i)||/||b|| 2.126345184557e-14 Linear solve converged due to CONVERGED_RTOL iterations 1 iter = 2, SNES Function norm 0.217885 0 KSP preconditioned resid norm 5.796196387015e+01 true resid norm 2.178851605144e-01 ||r(i)||/||b|| 1.000000000000e+00 1 KSP preconditioned resid norm 9.643306967470e-13 true resid norm 3.884638811957e-14 ||r(i)||/||b|| 1.782883608405e-13 Linear solve converged due to CONVERGED_RTOL iterations 1 iter = 3, SNES Function norm 0.217871 0 KSP preconditioned resid norm 3.792350832110e+01 true resid norm 2.178711262680e-01 ||r(i)||/||b|| 1.000000000000e+00 1 KSP preconditioned resid norm 1.369102629758e-12 true resid norm 1.632695466260e-13 ||r(i)||/||b|| 7.493858843196e-13 Linear solve converged due to CONVERGED_RTOL iterations 1 iter = 4, SNES Function norm 0.217839 0 KSP preconditioned resid norm 2.467674567895e+01 true resid norm 2.178387732479e-01 ||r(i)||/||b|| 1.000000000000e+00 1 KSP preconditioned resid norm 1.336018611676e-12 true resid norm 2.369440379931e-14 ||r(i)||/||b|| 1.087703692324e-13 Linear solve converged due to CONVERGED_RTOL iterations 1 iter = 5, SNES Function norm 0.217793 0 KSP preconditioned resid norm 1.325333377704e+01 true resid norm 2.177933144217e-01 ||r(i)||/||b|| 1.000000000000e+00 1 KSP preconditioned resid norm 2.663121116220e-13 true resid norm 6.399802508715e-15 ||r(i)||/||b|| 2.938475189519e-14 Linear solve converged due to CONVERGED_RTOL iterations 1 iter = 6, SNES Function norm 0.217546 0 KSP preconditioned resid norm 8.654271429945e+00 true resid norm 2.175456199462e-01 ||r(i)||/||b|| 1.000000000000e+00 1 KSP preconditioned resid norm 2.103027422078e-12 true resid norm 1.896269373207e-14 ||r(i)||/||b|| 8.716651586351e-14 Linear solve converged due to CONVERGED_RTOL iterations 1 iter = 7, SNES Function norm 0.217024 0 KSP preconditioned resid norm 5.238463146996e+00 true resid norm 2.170240974179e-01 ||r(i)||/||b|| 1.000000000000e+00 1 KSP preconditioned resid norm 1.538914082201e-13 true resid norm 1.398699322805e-14 ||r(i)||/||b|| 6.444903305426e-14 Linear solve converged due to CONVERGED_RTOL iterations 1 iter = 8, SNES Function norm 0.215661 0 KSP preconditioned resid norm 3.380654310210e+00 true resid norm 2.156611254980e-01 ||r(i)||/||b|| 1.000000000000e+00 1 KSP preconditioned resid norm 5.676163043758e-14 true resid norm 2.209776803347e-15 ||r(i)||/||b|| 1.024652355979e-14 Linear solve converged due to CONVERGED_RTOL iterations 1 iter = 9, SNES Function norm 0.213573 0 KSP preconditioned resid norm 1.833370627403e+00 true resid norm 2.135728351107e-01 ||r(i)||/||b|| 1.000000000000e+00 1 KSP preconditioned resid norm 1.237094085371e-13 true resid norm 3.167085089319e-15 ||r(i)||/||b|| 1.482906329205e-14 Linear solve converged due to CONVERGED_RTOL iterations 1 iter = 10, SNES Function norm 0.206951 0 KSP preconditioned resid norm 1.011617991320e+00 true resid norm 2.069514796799e-01 ||r(i)||/||b|| 1.000000000000e+00 1 KSP preconditioned resid norm 3.789650938118e-13 true resid norm 5.695302032970e-14 ||r(i)||/||b|| 2.751998701231e-13 Linear solve converged due to CONVERGED_RTOL iterations 1 Nonlinear solve did not converge due to DIVERGED_FUNCTION_COUNT iterations 10 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=11 total number of function evaluations=10623 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 5.81047 Factored matrix follows: Mat Object: 1 MPI processes type: seqaij rows=961, cols=961 package used to perform factorization: petsc total: nonzeros=38169, allocated nonzeros=38169 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=961, cols=961 total: nonzeros=6569, allocated nonzeros=15485 total number of mallocs used during MatSetValues calls =712 not using I-node routines I don't know why the program was terminated. I really need your help. Thanks, Yingjie
