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?
---
Roy
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