On 03/15/2013 03:16 PM, John Peterson wrote: > On Fri, Mar 15, 2013 at 1:15 PM, John Peterson <[email protected]> wrote: >> 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" > Wait, nevermind, you said FEMSystem, which is base on ImplicitSystem, > sorry. Those options won't do anything. Well, it did do something ... "-snes_linesearch_type basic" makes the solver do multiple linear solves instead. That does not make any sense to me as I'm just trying to solve Ax=b.
> ------------------------------------------------------------------------------ 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
