log and exp in math.h

FlyingNosehair

Does anyone know how the functions log and exp work in math.h or where I can find out how they work?

anthrax11

This didn't help?
[link=http://www.google.com/#hl=en&source=hp&q=log+exp+math.h]http://www.google.com/#hl=en&source=hp&q=log+exp+math.h[/link]

FlyingNosehair

Yes, that's right. It didn't. All I could find when I typed that or similar queries was information about their definitions (such as what type of variable they return, what type of variable they accept, and a brief description of what they do). I found nothing like information on how they were programmed. Nothing like source code for them.

FlyingNosehair

Come to think of it, maybe I should clarify what I mean. I don't simply want to know what to pass to the functions and what they return. I want to know how they work "under the covers". Do they use something like a Taylor series? Ideally, I'd like the source code for them.

anthrax11

I see. Well, I'm no expert on this, but I can point you to a couple of open-source implementations of libc. Here you can find the math functions not specific to a platform (if I understand correctly):
http://sourceware.org/git/?p=glibc.git;a=tree;f=math;
[link=http://git.uclibc.org/uClibc/tree/libm]http://git.uclibc.org/uClibc/tree/libm[/link]

The platform-dependant implementations of log and exp can be found in the sysdeps directory. Look for the fpu directory under each of the platform directories.
http://sourceware.org/git/?p=glibc.git;a=tree;f=sysdeps;

You can also get a local copy of the whole library for easier access:
[link=http://ftp.gnu.org/gnu/glibc/]http://ftp.gnu.org/gnu/glibc/[/link]

I hope this helps.

FlyingNosehair

Thanks, it did.