[SciPy-User] optimize.fmin_cg terminates when w - grad*1e-10 yields lower obj & grad
Mon Oct 5 13:35:23 CDT 2009
On Mon, Oct 5, 2009 at 1:53 PM, Jason Rennie <firstname.lastname@example.org> wrote:
> On Mon, Oct 5, 2009 at 1:40 PM, <email@example.com> wrote:
>> Does lowering gtol help? e.g. gtol=1e-10
>> I would keep using norm=inf to force more iterations.
> Thanks for the suggestion, but no, it does not seem to help. I get the same
> exact behavior with no norm argument (default is Inf) and a gtol=1e-10
In this case, I either agree with Sebastian, or you are already at a minimum
up to the usual precision, or your problem is badly scaled (my next guesses).
In your initial example, you had an improvement with a stepsize 1e-10,
however fmin_cg has a minimum stepsize of amin = 1e-8 (hardcoded) in linesearch
if my very fast skimming of the code is correct.
I don't know about fmin_cg but, if I remember correctly, I got this return code
with other minimizers when I had an (almost) perfect fit, with no noise in the
simulation. Otherwise, you could try to rescale your problem to make the
parameters larger in absolute value.
> Jason Rennie
> Research Scientist, ITA Software
> SciPy-User mailing list
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