From: Brian Gough <bjg@network-theory.co.uk>
To: Philippe Huber <huberph@infomaniak.ch>
Cc: gsl-discuss@sources.redhat.com
Subject: Re: Proposition of a better convergion criterion in multimin
Date: Mon, 26 Aug 2002 13:12:00 -0000 [thread overview]
Message-ID: <15722.35587.116438.176395@debian> (raw)
In-Reply-To: <000001c248f6$e7394500$7e28c281@osiris>
Philippe Huber writes:
> I found that the stopping criterion proposed in
> gsl_multimin_test_gradient suffers from scale problems. Typically,
> if you have variables of magnitude 1.0e0 and a function of
> magnitude 1.0e5, it can be impossible to minimize the norm of the
> gradient under 1.0e-2. Dennis and Schnabel in "Numerical Methods
> for Unconstrained Optimization and Nonlinear Equations", p.160
> propose another criterion: relgrad = gradfi * xi / f, where gradfi
> is the ith component of the gradient and xi the ith variable. The
> criterion is ||relgrad||inf < epsabs, with ||.||inf is the infinite
> norm: ||x||inf=max(|xi|). Here is a proposition of a new routine
> called gsl_multimin_test_relgrad:
How about scaling the components of g? This would be invariant under
x->x+constant, f->f+constant which seems like a useful property.
prev parent reply other threads:[~2002-08-26 20:12 UTC|newest]
Thread overview: 2+ messages / expand[flat|nested] mbox.gz Atom feed top
2002-08-21 2:41 Philippe Huber
2002-08-26 13:12 ` Brian Gough [this message]
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