The linear solver did not fail to converge. It says it converged. The nonlinear solver failed because the line search failed, not the linear solver. This is common when the changes are tiny, tiny like they are here. You cannot expect that corrections that are the same size as the round error to improve the nonlinear system. That is your initial guess is so small you cannot do any better.
I will change the LS in the message to line_search for clarity in petsc-dev Barry On Sep 10, 2010, at 9:54 AM, Rebecca Xuefei Yuan wrote: > Dear all, > > I have the convergence history as > > > > 0 SNES Function norm 1.930639214656e-14 > 0 KSP Residual norm 1.930639214656e-14 > 1 KSP Residual norm 1.897969082784e-14 > 2 KSP Residual norm 1.890943705731e-14 > 3 KSP Residual norm 1.890499250642e-14 > 4 KSP Residual norm 1.882719263807e-14 > 5 KSP Residual norm 1.881639616800e-14 > 6 KSP Residual norm 1.881624492545e-14 > 7 KSP Residual norm 1.876497311488e-14 > 8 KSP Residual norm 1.864714377471e-14 > 9 KSP Residual norm 1.861061216430e-14 > 10 KSP Residual norm 1.856993815540e-14 > 11 KSP Residual norm 1.856245191617e-14 > 12 KSP Residual norm 1.855993722295e-14 > 13 KSP Residual norm 1.855756795426e-14 > 14 KSP Residual norm 1.855542358114e-14 > 15 KSP Residual norm 1.855188622531e-14 > 16 KSP Residual norm 1.854906019037e-14 > 17 KSP Residual norm 1.851397858397e-14 > 18 KSP Residual norm 1.851152033377e-14 > 19 KSP Residual norm 1.845662066987e-14 > 20 KSP Residual norm 1.810881990601e-14 > 21 KSP Residual norm 9.715701270773e-15 > 22 KSP Residual norm 2.134473951854e-15 > Linear solve converged due to CONVERGED_RTOL iterations 22 > Nonlinear solve did not converge due to DIVERGED_LS_FAILURE > > Why the linear solver is failed? > > Thanks a lot! > > > > > > Rebecca Xuefei YUAN > Department of Applied Physics and Applied Mathematics > Columbia University > Tel:917-399-8032 > www.columbia.edu/~xy2102 >
