On Tue, 2007-09-04 at 18:17 -0500, Mike McCarty wrote: > Matthew Saltzman wrote: > > On Sat, 2007-09-01 at 09:41 -0500, Michael Hennebry wrote: > > > > > >>How much precision do you need? On what? Why? > >> > >>At least one person wrote a book on implementing the C standard library. > >>It would probably be a better resource than Numerical Recipes. > > > > > > That would be PJ Plauger's The Standard C Library, Prentice Hall, 1992 > > 0-13-131509-9. Most of his math lib implementation is based on Cody and > > Waite, Software Manual for the Elementary Functions, Prentice Hall, 1980 > > (sorry, he doesn't give the ISBN). > > My copy of Cody & Waite is ISBN 0-13-822064-6. The exact title > is "Software Manual for the Elementary Functions". > > I'm afraid I'm not very impressed with "Numerical Recipes". > I bought a copy many years ago, and found some humorous lapses > in the multi-precision FFT based math package. Things which > proved that they don't know what they are doing, I'm afraid. > Like subtracting one float from another repeatedly in a loop > instead of using fmod(). Early NR, especially NR in C, had some real laughers. (BTW, does Fortran 77 have an equivalent to fmod()?. If not, that might explain where they picked up the repeated subtraction idea. They really didn't know much C back in the early days...) I haven't seen any reviews yet, but the third edition is just now coming out, after 15 years. More information at http://www.nr.com. (I'm not endorsing anything here. I have no affiliation with anyone involved with NR.) > > I've had good results with Cody & Waite, though it's getting > somewhat dated (1980) and some better stuff has come along, > or so I've heard. > > But, if the hardware is being used, then coding something with > less accuracy is also going to be slower. Still may depend on the processor and exactly what instructions are executed doing the approximation. Just because it's hardware, that doesn't mean it will necessarily take only a few clock cycles. > > Mike -- Matthew Saltzman Clemson University Math Sciences mjs AT clemson DOT edu http://www.math.clemson.edu/~mjs
