Date: Sat, 1 Oct 2016 10:52:14 +0200 From: Markus Wichmann <nullplan@....net> To: musl@...ts.openwall.com Subject: Re: Model specific optimizations? On Sat, Oct 01, 2016 at 01:50:23AM -0400, Rich Felker wrote: > I don't think this works at all. sqrt() is required to be > correctly-rounded; that's the whole reason sqrt.c is costly. It's an approximation, at least, which was rather my point. As I've come to realize over the course of this discussion, the fsqrt instruction is useless here and pretty much everywhere out there: - If you are looking for accuracy over speed, the standard C library has got you covered. - If you are looking for speed over accuracy, you can code up the Babylonian method inside five minutes. You can even tune it to suit your needs to an extent (mainly, number of rounds and method of first approximation). This method is also portable to other architectures, and can be done entirely in C (requiring IEEE floating point, but then, most serious FP code does that). Also, at least according to Apple, which were the only ones actually looking at the thing, such as I could find, it was only ever supported by the 970 and the 970FX cores, released in 2002 and 2004, respectively. I highly doubt they'll have much relevance. Chalk up my suspicions from the OP to not having researched enough. In closing: Nice discussion, but I'm sorry for the noise. Ciao, Markus
Powered by blists - more mailing lists
Confused about mailing lists and their use? Read about mailing lists on Wikipedia and check out these guidelines on proper formatting of your messages.