Implementing Cosine in C from Scratch

• musl

  17 169 8.6 C

  unofficial musl mirror git://git.musl-libc.org/musl (by ifduyue)

• pure-data

  8 1,457 9.4 C

  Pure Data - a free real-time computer music system

  

• WorkOS

  workos.com sponsored

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• scratch-www

  803 1,559 9.9 JavaScript

  Standalone web client for Scratch

  

Now, anyone that wants to know sin(A) just has to read that sprite's X and Y position.

[0]: https://scratch.mit.edu

• v7unix

  5 74 2.7 C

  Version 7 Unix for a POSIX world

  

This takes me back in time, to c. 1982 when I got curious about how computers calculated trig functions. Luckily I was using one of the first OSS systems (modulo AT&T lawyers): Unix V7. So I pulled up the source and took a look. You can still see it here: https://github.com/v7unix/v7unix/blob/master/v7/usr/src/libm...

• supercollider

  64 5,198 8.4 C++

  An audio server, programming language, and IDE for sound synthesis and algorithmic composition.

  

• vectrig

  1 6 10.0 C

  Vectorized approximate trigonometry library optimized for GCC

Thanks for explaining this. I actually wrote a SIMD implementation of trig functions years ago, using the techniques you describe.

You can check it out: https://github.com/jeremysalwen/vectrig

I compared several different methods of generating polynomials of different sizes for speed and precision (spoilers: taylor series were the worst and minimax polynomials (Remez algorithm) were the best).

Another (surprising) thing which I learned during the project was that the range reduction was just as (if not more) important to the accuracy of the implementation than the polynomial. If you think about it, you will realize that it's actually pretty difficult to quickly and accurately compute the sin of large numbers like 2^50.

I also tried to directly optimize the coefficients for the accuracy of the polynomial on the required range, but that experiment was unsuccessful.

It's all there in the repository, the implementations, notes about the different polynomials used, and the accuracy/speed statistics for the different methods.

• wefx

  4 27 4.9 C

  Basic WASM graphics package to draw to an HTML Canvas using C. In the style of the gfx library

I haven’t seen this version mentioned in the thread - if you don’t need a lot of precision, here is a simple 4 line version[1] and here’s how it works[2].

Not sure who initially came up with it.

[1] https://github.com/robrohan/wefx/blob/1a918cc2d5ad87402a3830...

[2] https://www.desmos.com/calculator/lo7cf60mjz

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