On Fri, Mar 15, 2013 at 1:03 PM, Roy Stogner <[email protected]> wrote: > > On Fri, 15 Mar 2013, Jens Lohne Eftang wrote: > >> On 03/15/2013 02:01 PM, Roy Stogner wrote: >>> >>> I'd start by turning on PETSc's monitor flags ('-ksp_monitor' etc?). >>> Endless residual reevaluations suggests to me that the initial >>> linear solve converged poorly and didn't give you a descent direction, >>> and a subsequent line search is failing to find a reduced nonlinear >>> residual. >> It seems to me that the residual gets assembled after the solver has >> converged, for some reason. > > Yes: After you take a Newton step, the Newton solver typically wants > to make sure that that step gave you a (nonlinear) residual reduction, > and to see whether that new residual meets your tolerances so that the > Newton iteration can claim convergence and exit. > > If you got a good linear solve (so the new proposed solution is a > descent direction) but the next nonlinear residual is lousy, then > typically the next operation is a line search, which does a whole > bunch more residual evaluations at points in between the solution at > the previous nonlinear solve and the failed proposed next step. > > But it looks like you're getting a good linear solve yet not getting a > good line search result. Is it possible your residual and Jacobian > aren't consistent?
Petsc 3.3? You can also try "-snes_linesearch_type basic" to turn linesearch off completely Prior to 3.3 it was "-snes_ls basic" -- John ------------------------------------------------------------------------------ Everyone hates slow websites. So do we. Make your web apps faster with AppDynamics Download AppDynamics Lite for free today: http://p.sf.net/sfu/appdyn_d2d_mar _______________________________________________ Libmesh-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/libmesh-users
