On 03/15/2013 03:24 PM, John Peterson wrote: > On Fri, Mar 15, 2013 at 1:19 PM, Jens Lohne Eftang <[email protected]> wrote: >> 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. > Well I think FEMSystem solves everything as though it were nonlinear. > So if you make your ksp_rtol (linear tolerance) about the same as your > nonlinear tolerance, the "nonlinear" solver should converge in 1 > iteration. Right, but the norm of my residual stays at 0.403898 after the first (and every consecutive) linear solve. So it's got to be something with my assemblies then.
In element_time_derivative is it correct that I should only assemble the jacobian if request_jacobian == true? ------------------------------------------------------------------------------ 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
