From mboxrd@z Thu Jan 1 00:00:00 1970 X-Msuck: nntp://news.gmane.org/gmane.linux.lib.musl.general/13691 Path: news.gmane.org!.POSTED.blaine.gmane.org!not-for-mail From: Damian McGuckin Newsgroups: gmane.linux.lib.musl.general Subject: Re: Possible Mistype in exp.c Date: Wed, 30 Jan 2019 22:14:01 +1100 (AEDT) Message-ID: References: <20190129110135.GC21289@port70.net> <20190129114308.GD21289@port70.net> <20190130093738.GE21289@port70.net> Reply-To: musl@lists.openwall.com Mime-Version: 1.0 Content-Type: TEXT/PLAIN; format=flowed; charset=US-ASCII Injection-Info: blaine.gmane.org; posting-host="blaine.gmane.org:195.159.176.226"; logging-data="89011"; mail-complaints-to="usenet@blaine.gmane.org" User-Agent: Alpine 2.02 (LRH 1266 2009-07-14) Cc: musl@lists.openwall.com To: Szabolcs Nagy Original-X-From: musl-return-13707-gllmg-musl=m.gmane.org@lists.openwall.com Wed Jan 30 12:14:19 2019 Return-path: Envelope-to: gllmg-musl@m.gmane.org Original-Received: from mother.openwall.net ([195.42.179.200]) by blaine.gmane.org with smtp (Exim 4.89) (envelope-from ) id 1gonox-000N37-KD for gllmg-musl@m.gmane.org; Wed, 30 Jan 2019 12:14:19 +0100 Original-Received: (qmail 23711 invoked by uid 550); 30 Jan 2019 11:14:17 -0000 Mailing-List: contact musl-help@lists.openwall.com; run by ezmlm Precedence: bulk List-Post: List-Help: List-Unsubscribe: List-Subscribe: List-ID: Original-Received: (qmail 23684 invoked from network); 30 Jan 2019 11:14:16 -0000 X-Authentication-Warning: key0.esi.com.au: damianm owned process doing -bs In-Reply-To: <20190130093738.GE21289@port70.net> Xref: news.gmane.org gmane.linux.lib.musl.general:13691 Archived-At: On Wed, 30 Jan 2019, Szabolcs Nagy wrote: > i work at arm and i did this work there so i know the background. That explains everything. > there is not much published about the algorithms (although there aren't > many new ideas in the code, Sadly, a lot of the existing ideas are not documented well. Even the texts on this topic seem to be lacking all the information to actually implement a fast low-level routine. They cover fundamentals well and important topics like error analysis but omit the basic techniques and little details and basic techniques that are needed to make it fast and still achieve that 1*ULP (or better) error bound. > it's mostly about optimizing for modern cpus), but i plan to at least > put the polynomial and lookup table generation code in that repo. Thanks. For some reason, I have this aversion to table lookup because suddenly there are lots more numbers hanging about. But, it certainly helps to achieve optimal performance. I had a look at the GLIBC exp.c which comes out of the Ultimate Libray done by IBM and I find that inpossible to read/comprehend especially with its table lookups. > the polynomial coefficients were generated with the sollya tool from > inria. Yes, nice tool. What range reduction is used for those routines and why are there several polynomials? Just curious. Regards - Damian Pacific Engineering Systems International, 277-279 Broadway, Glebe NSW 2037 Ph:+61-2-8571-0847 .. Fx:+61-2-9692-9623 | unsolicited email not wanted here Views & opinions here are mine and not those of any past or present employer