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On Fri, 29 Sep 2000, Van Snyder wrote: > easy. As one reads NR, one also gains the impression that both the > reader and the authors understand the material completely. > > Unfortunately, none of this is true. I have mixed feelings about the NR books. Since I have purchased both F77 and F90 volumes myself, I have a legal copy of the routines on disc. From time to time I get colleagues asking if they can use the code. I have to explain (a) the copyright restrictions, and (b) the questionable quality of the code. Almost anyone can appreciate the lack of sensible error-handling if it is pointed out to them. But I still think that the NR volumes are extremely valuable. Very few scientists are competenent in numerical analysis, and the most we can hope for is a short course on it as undergraduates (which quickly gets forgotten). When we come across some problem in the field, there's a problem. Scientists are reluctant to use a black box without understanding how it works, and standard library routines often seem unnecessarily complex and hard to use. I think that NR fulfils a valuable function in explaining in language that the average scientist can understand, the basic principles. If that deters some of them from trying to write their own code to solve their current problem, then that alone is a valuable function. If it makes them understand how the routine from some standard library (like NAG) works, at least in outline, then that is also valuable. The fact that the NR books include code, helps me to understand what they are talking about. So I'm a modest supporter. I have learnt a lot from the NR books, and I can't say that about any other tomes on numerical analysis. > This will continue to be true so long as the authors of NR pursue > overly-simple solutions to complex problems, or continue to describe > methods that have been obsolete for decades. It would be nice to have examples of these - I've seen a number of critiques of the algorithms, but most seem to be of the type that I'd call "nit-picking". I haven't seen any examples of techniques they advocate which are wholly obsolete. -- Clive Page, Dept of Physics & Astronomy, University of Leicester. %%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%%