On Tue, Dec 25, 2001, Shlomi Fish wrote about "Re: Implementation of log(x) for SPARC32": > Actually, usually glibc calls the processor's FPU logarithm routine.
Oops, I didn't know the 386DX's FPU had a logarithm function on it... Nice :) Do they also have things like sqrt and cbrt? > I did not say it is i386 specific. I'm sure it works fine on SPARCs. > However, with things like math, there are separate routines for each > architecture. And the SPARC's one is too obfuscated, and I cannot > understand how I can rip the relevant code. Maybe SPARC doesn't have a magic-logarithm-blackbox on its CPU or FPU, so it must use an actual algorithm to find the log - which is why it looks more obfuscated than a simple call-the-fpu code. > FYI, I eventually gave up and coded a logarithm function in perl: >.. > Works like a charm with exactly the same accuracy. I'm going to convert it > to C, and by this I will have a truly portable log() implementation for > the kernel. Inventing your own wheels again, are you? :) Your algorithm works, no doubt. So will nearly any other algorithm you'll divise. What I doubt is that you can't do the same thing with half the number of floating-point calculations (divisions, additions, comparisons), so if you care about performance (maybe you don't, I don't know) you might want to look for the *best* known algorithm, not just *an* algorithm. Maybe your algorithm is alread the best possible - I don't know; In that case, congradulations :) > IMO, someone should port stuff like a large part of glibc as well as STL, > etc to the kernel. That would make the lives of programmers much easier > because they won't have to reinvent the wheel times and again. But it will make the kernel huge... And nobody needs logarithms or bessel functions and such stuff in the kernel anyway, except perhaps your very specialized module. Next thing, you'll be asking to put a Java virtual machine inside the kernel. It would have been useful to run syscalltrack expressions ;) -- Nadav Har'El | Tuesday, Dec 25 2001, 10 Tevet 5762 [EMAIL PROTECTED] |----------------------------------------- Phone: +972-53-245868, ICQ 13349191 |Seen on the back of a dump truck: http://nadav.harel.org.il |<---PASSING SIDE . . . . . SUICIDE---> ================================================================= To unsubscribe, send mail to [EMAIL PROTECTED] with the word "unsubscribe" in the message body, e.g., run the command echo unsubscribe | mail [EMAIL PROTECTED]
