Floating-Point Determinism (2013)(randomascii.wordpress.com)

57 pointsby antioedipus8 tahun yang lalu6 comments

randomascii.wordpress.com

Floating-Point Determinism (2013)

https://randomascii.wordpress.com/2013/07/16/floating-point-determinism/

6 comments

strainer8 tahun yang lalu

I rewrote the main trig functions in Javascript to help with cross browser determinism. They run as quickly as the native math routines while compromising accuracy to around 10 significant digits.

https://github.com/strainer/trigfills

sour-taste8 tahun yang lalu

Excellent article. It's so easy to think "same inputs = same outputs" but that's such a simplification. There's so much more in between!

gbrown_8 tahun yang lalu

For anyone interested in this sort of thing you'd probably also be interested in John Gustafson's work on unums/posits. Here's a nice introductory presentation https://www.youtube.com/watch?v=aP0Y1uAA-2Y

olliej8 tahun yang lalu

I’m glad it pointed to the article of the terrible accuracy of the x87 trig functions - the OS X and I assume GCC software implementations are ostensibly correctly accurate, which I think is done by using witchcraft. (More precisely I think they do it using infinite precision Pi?)

brucedawson8 tahun yang lalu

Correctly rounded trig functions requires great care, and some way of knowing how much precision you need for the calculations. Doing all of the calculations at the maximum needed precision would be hugely inefficient. A high-precision version of Pi is just one of the things needed.

olliej8 tahun yang lalu

What I had been told was that they commuted "as if" they had infinite precision pi (rather than reduction modulo some approximation)