From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 2590 invoked by alias); 14 Jul 2002 21:05:35 -0000 Mailing-List: contact gsl-discuss-help@sources.redhat.com; run by ezmlm Precedence: bulk List-Subscribe: List-Archive: List-Post: List-Help: , Sender: gsl-discuss-owner@sources.redhat.com Received: (qmail 2508 invoked from network); 14 Jul 2002 21:05:34 -0000 Received: from unknown (HELO mail7.svr.pol.co.uk) (195.92.193.21) by sources.redhat.com with SMTP; 14 Jul 2002 21:05:34 -0000 Received: from modem-38.chromis.dialup.pol.co.uk ([62.136.245.38] helo=localhost) by mail7.svr.pol.co.uk with esmtp (Exim 3.35 #1) id 17TqYf-0008QL-00; Sun, 14 Jul 2002 22:05:33 +0100 Received: by network-theory.co.uk via sendmail from stdin id (Debian Smail3.2.0.102) for tlb@tlb.org; Sun, 14 Jul 2002 21:34:23 +0100 (BST) From: Brian Gough MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Message-ID: <15665.57423.817466.370459@debian> Date: Sun, 14 Jul 2002 14:05:00 -0000 To: tlb@tlb.org Cc: gsl-discuss@sources.redhat.com Subject: Re: multifit_nlin on linear data In-Reply-To: <200207122024.g6CKODl4055949@tlb.blackwells.net> References: <200207122024.g6CKODl4055949@tlb.blackwells.net> X-SW-Source: 2002-q3/txt/msg00057.txt.bz2 tlb@tlb.org writes: > I have a multiparameter fitting problem which is nonlinear in general, > but has linear behavior in some regions where I can exactly calculate > the derivatives. So sometimes when I use gsl_multifit_fdfsolver it's > able to jump to the correct solution in a single jump, as you'd expect > it to. > > Should I be using a different termination critereon than > gsl_multifit_test_delta? I'd recommend using a different termination criterion. The step size is not a reliable indicator on its own. ETOLF indicates that the algorithm can't go any further downhill, so you can usually take that as signalling a minimum if you know that the behavior of the function is reasonable. regards Brian Gough