From mboxrd@z Thu Jan 1 00:00:00 1970 From: Mikael Adlers To: "'jonathan@leto.net'" , gsl-discuss@sources.redhat.com Subject: RE: Root finding page manual suggestion Date: Wed, 19 Dec 2001 13:20:00 -0000 Message-id: <4DFD94A38EB3104E838576A77AEBB36E166DC8@hermes.mathcore.se> X-SW-Source: 2001/msg00631.html Hi, I agree with the warning. The book you refereed to "Numerical recipes" by W. H. Press S.A Teukolsky et. al. is not regarded by numerical analysis's as anything worth reading. The algorithms are old and not so good implemented. Even the references are bad (how can anyone implement linear algebra algorithms without including any references to Golub or van Loan?) The only bright part with the book is that they cover much in an easy way and book is quite cheap. Potorti on the other hand refereed to the book "Numerical methods" by Dalquist and Björck. Two of the most leading numerical analysis's in the field of ODE and linear algebra. This book is worth reading but starts to become quite old. I know that a new book, "Numerical Mathematics" in several volumes will soon be published by SIAM. I can really recommend this book as a reference work when it becomes available. Regards, /Mikael Adlers BTW. the choice of when to use the Newton or the secant method is still present Numerical Mathematics (together with the derivation of the rule). ------------------------------------------------------------------ Mikael Adlers, Ph.D. email: mikael@mathcore.com MathCore AB phone: +4613 32 85 07 Wallenbergsgata 4 fax: 21 27 01 SE-583 35 Linköping, Sweden http://www.mathcore.com > -----Original Message----- > From: Jonathan Leto [ mailto:jonathan@leto.net ] > Sent: den 19 oktober 2001 04:08 > To: Francesco Potorti` > Cc: gsl-discuss@sources.redhat.com > Subject: Re: Root finding page manual suggestion > > > Just as a word of warning, I found a interesting site called > "Why not use Numerical Recipes?", written by JPL. > Link: http://math.jpl.nasa.gov/nr/ > > It seems that a few professional numerical analysts have found > quite a few things wrong with much of the code and theory. > > > Francesco Potorti` (pot@gnu.org) was saying: > > > In the "Root Finding Algorithms using Derivatives" page one reads that > > the Newton's method converges quadratically for single roots, while the > > secant method has 1.6 convergence order, and "can be useful when > > computation of the derivative is costly". > > > > In fact, as far as I know, it is almost always preferable to Newton's > > method. > > > > Quoting from "Numerical Methods" by Germund Dahlquist and Ake Bjorck, > > translated by Ned Anderson - Prentice-Hall Inc., 1974. > > > > Chapter 6.4.1. (the end) pg 229 > > The choice between the secant method and Newton-Raphson's method > > depends on the amount of work required to compute f'(x). Suppose the > > amount of work to compute f'(x) is T times the amouof work to > > compute a value of f(x). Then an asymptotic analysis can be used to > > motivate the rule: if T > 0.44, then use the secant method; otherwise, > > use Newton-Raphson's method. > > > > I've used this criterion in some small numerical program I've written, > > and it works ok. The above means that Newton's method wins only if > > computing f'(x) is more than twice faster than computing f(x), a quite > > rare occurrence in practice. I suggest this fact to be mentioned in the > > manual. > > > > Please Cc to me while replying, as I am not subscribed to the list. > > -- > jonathan@leto.net > "Wir mussen wissen. Wir werden wissen." > > >