From mboxrd@z Thu Jan 1 00:00:00 1970 X-Spam-Checker-Version: SpamAssassin 3.4.4 (2020-01-24) on polar.synack.me X-Spam-Level: X-Spam-Status: No, score=-1.9 required=5.0 tests=BAYES_00 autolearn=ham autolearn_force=no version=3.4.4 X-Google-Thread: 103376,890e7bb13b3c2a7f X-Google-NewGroupId: yes X-Google-Attributes: gida07f3367d7,domainid0,public,usenet X-Google-Language: ENGLISH,ASCII-7-bit Received: by 10.66.72.42 with SMTP id a10mr242704pav.34.1350642683443; Fri, 19 Oct 2012 03:31:23 -0700 (PDT) Received: by 10.68.219.198 with SMTP id pq6mr242738pbc.0.1350642683423; Fri, 19 Oct 2012 03:31:23 -0700 (PDT) Path: s9ni21683pbb.0!nntp.google.com!kt20no4375950pbb.1!postnews.google.com!glegroupsg2000goo.googlegroups.com!not-for-mail Newsgroups: comp.lang.ada Date: Fri, 19 Oct 2012 03:31:23 -0700 (PDT) In-Reply-To: Complaints-To: groups-abuse@google.com Injection-Info: glegroupsg2000goo.googlegroups.com; posting-host=97.117.199.50; posting-account=x5rpZwoAAABMN2XPwcebPWPkebpwQNJG NNTP-Posting-Host: 97.117.199.50 References: <29fc1667-46f8-40b5-aef9-bea87dc862b4@googlegroups.com> User-Agent: G2/1.0 MIME-Version: 1.0 Message-ID: <6b1e1af2-d9d0-47ce-a333-b54e979155ac@googlegroups.com> Subject: Re: How to get high-precision floating point--MPFR From: Jerry Cc: mailbox@dmitry-kazakov.de Injection-Date: Fri, 19 Oct 2012 10:31:23 +0000 Content-Type: text/plain; charset=ISO-8859-1 Date: 2012-10-19T03:31:23-07:00 List-Id: On Friday, October 19, 2012 2:45:06 AM UTC-7, Dmitry A. Kazakov wrote: > On Fri, 19 Oct 2012 01:57:19 -0700 (PDT), Jerry wrote: > > > And why is the Ada type using less > > mantissa bits than the hardware? > > AFAIK x86/x86-64 do not have hardware 128-bit floats (IEEE or not). See > > http://en.wikipedia.org/wiki/Quadruple-precision_floating-point_format > > Which also says that gcc's long double is merely 80-bit extended precision. > That, I presume, corresponds to the GNAT's Long_Long_Float. That makes sense. I think I once knew that. > You could compare attributes of Long_Long_Float and > Interfaces.C.long_double, The same program reports: In Interfaces.C, long_double bits is 128 T'Machine_Mantissa (A.5.3), in particular, it > should be 64 for 80-bit extended precision. > > Why GNAT uses 128 bit instead of 80 actually used bit? Maybe, because of > alignment issues. > > -- > Regards, > Dmitry A. Kazakov > http://www.dmitry-kazakov.de