From mboxrd@z Thu Jan 1 00:00:00 1970 Return-Path: Received: (qmail 126589 invoked by alias); 16 Nov 2015 22:07:06 -0000 Mailing-List: contact libc-alpha-help@sourceware.org; run by ezmlm Precedence: bulk List-Id: List-Subscribe: List-Archive: List-Post: List-Help: , Sender: libc-alpha-owner@sourceware.org Received: (qmail 126575 invoked by uid 89); 16 Nov 2015 22:07:05 -0000 Authentication-Results: sourceware.org; auth=none X-Virus-Found: No X-Spam-SWARE-Status: No, score=-0.4 required=5.0 tests=AWL,BAYES_00,KAM_LAZY_DOMAIN_SECURITY,RCVD_IN_DNSWL_LOW,SPF_HELO_PASS autolearn=no version=3.3.2 X-HELO: sonata.ens-lyon.org Message-ID: <564A53CE.8080500@lip6.fr> Date: Mon, 16 Nov 2015 22:07:00 -0000 From: Christoph Lauter User-Agent: Mozilla/5.0 (X11; Linux x86_64; rv:31.0) Gecko/20100101 Icedove/31.8.0 MIME-Version: 1.0 To: Joseph Myers , "Paul E. Murphy" CC: "libc-alpha@sourceware.org" , Steve Munroe , Tulio Magno Quites Machado Filho , Michael R Meissner Subject: Re: IEEE128 binary float to decimal float conversion routines References: <564A16D5.3020105@linux.vnet.ibm.com> In-Reply-To: Content-Type: text/plain; charset=windows-1252; format=flowed Content-Transfer-Encoding: 8bit X-SW-Source: 2015-11/txt/msg00324.txt.bz2 Hi everyone, Joseph Myers wrote on 11/16/2015 07:24 PM: > The BID conversions between binary and decimal float involve several MB of > tables (whereas libgcc DPD conversions go via strings). Several MB of > tables are not of course needed; if doing correctly-rounded conversions > (required for IEEE 754 conformance) there's a speed/space trade-off in how > much precomputed data you use versus how much computation you do at > runtime, and it's up to you what you think the right trade-off for powerpc > is. > For what it's worth: some colleagues of mine and myself have recently published a paper on exact binary-to-decimal conversions between all IEEE754 formats, assuming BID as the encoding for decimal. None of the algorithms we proposed uses a table larger that a couple of dozens of kilobytes. Converting between binary and decimal FP with correct rounding is essentially the same problem, so people might wish to have a look at these results: > http://www.computer.org/csdl/trans/tc/preprint/07271015-abs.html Best regards, Christoph Lauter -- Christoph Lauter Maître de conférences - Associate Professor Équipe PEQUAN - LIP6 - UPMC Paris 6 4, place Jussieu, 75252 Paris Cedex 05, 26-00/301 Tel.: +33144278029 / +33182521777 http://www.christoph-lauter.org/