On Fri, May 15, 2015 at 6:37 PM, Mark Lohry <[email protected]> wrote:
> I'm having an issue with SNES where the regular newton line search
> severely overshoots the solution update, ending up with irrecoverable
> values (negative densities and temperatures in a fluids code), so it seems
> newtonTR is a better way to go.
>
> the manual says to set delta0 using -snes_tr_delta0, where the trust
> region radius is delta = delta0 * norm2( F ). My F values aren't well
> scaled and have pretty different values so norm2 of the whole thing isn't
> particularly meaningful. Ideally I'd like to tell SNES to limit the update
> to say, 10% of the current value of any given unknown. Is this possible?
>
1) The best thing you can do for solver convergence is to start with a
well-scaled system. Is there a reason why
you cannot non-dimensionalize your system?
2) Writing a custom line search is easier than messing with TR in my
experience
3) If you have constraints on the variables, you might benefit from using
SNESVI
Thanks,
Matt
--
What most experimenters take for granted before they begin their
experiments is infinitely more interesting than any results to which their
experiments lead.
-- Norbert Wiener
