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: 103376,6a8952cbe009f3ed X-Google-NewGroupId: yes X-Google-Attributes: gida07f3367d7,domainid0,public,usenet X-Google-Language: ENGLISH,ASCII-7-bit X-Received: by 10.180.93.134 with SMTP id cu6mr1360949wib.5.1359115745270; Fri, 25 Jan 2013 04:09:05 -0800 (PST) Path: o9ni19014wio.1!nntp.google.com!feeder1-2.proxad.net!proxad.net!feeder1-1.proxad.net!ecngs!feeder2.ecngs.de!feeder.erje.net!eu.feeder.erje.net!eternal-september.org!feeder.eternal-september.org!mx04.eternal-september.org!.POSTED!not-for-mail From: Paul Colin Gloster Newsgroups: comp.lang.ada Subject: Re: Numerical calculations: Why not use fixed point types for everything? Date: Fri, 25 Jan 2013 12:09:05 +0000 (UTC) Organization: A noiseless patient Spider Message-ID: References: <4905b963-0036-4129-8050-fb26ef0154d6@googlegroups.com> <32314026-23ae-45b8-a4c5-e589e7d79de2@googlegroups.com> <7aeff757-a038-45e0-93d6-bd1d6e02093e@googlegroups.com> Mime-Version: 1.0 Injection-Date: Fri, 25 Jan 2013 12:09:05 +0000 (UTC) Injection-Info: mx04.eternal-september.org; posting-host="2da593c5dc84c37dabca6edf3693dfa1"; logging-data="8301"; mail-complaints-to="abuse@eternal-september.org"; posting-account="U2FsdGVkX18IpEexdhSmvLOXLiHEGCur0FLnV2D8tTu57YR2UAOttQ==" User-Agent: slrn/0.9.9p1 (Linux) Cancel-Lock: sha1:zTHKEAXPn4sh0RfbWW9jue15KIU= Content-Type: text/plain; charset=us-ascii Content-Transfer-Encoding: 7bit Date: 2013-01-25T12:09:05+00:00 List-Id: On 2013-01-18, Randy Brukardt sent: |-----------------------------------------------------------------------------| |""Adam Beneschan" wrote in message | |news:7aeff757-a038-45e0-93d6-bd1d6e02093e@googlegroups.com... | |... | |>What I mean is that some processors (including the Pentium) have | |>instructions | |>to perform mathematical operations like trig functions, square-root, etc., | |>on | |>floating-point numbers, and special hardware to do the computation. | | | |We're talking Ada here, and in at least some cases (i.e. Intel processors), | |at least, those instructions aren't accurate enough to meet the requirements | |of Annex G for those mathematical operations. So it's unlikely that your | |compiler would use them (unless of course Annex G isn't supported at all, in | |which case you have no idea what the math actually does)." | |-----------------------------------------------------------------------------| During a VHDL-standardization meeting, David Bishop mentioned that a widespread, non-VHDL supposed implementation of a mathematical function was very wrong even within the supposedly supported bitwidth. |-----------------------------------------------------------------------------| |"So I find this to be a red herring: most Ada software uses only software | |trig functions and the like. [. . .] | | | |[. . .]" | |-----------------------------------------------------------------------------| Recent hardware lacks 128-bit floating-point support regardless of language. For example, from HTTP://software.Intel.com/en-us/forums/topic/304052?wapkw=quadruple : ##################################################################### #"[. . .] # # # # TimP (Intel) # #Tue, 11/27/2007 - 05:51 # # # #ifort real*16 (113 bits precision) is implemented on Xeon CPUs by # #functions which combine x87 operations, so the performance is quite# #low [. . .] # # # #[. . .]" # ##################################################################### Similarly from WWW.PGroup.com/userforum/viewtopic.php?t=127&highlight=double+emulation : !-----------------------------------------------------------------------! !"[. . .] ! ! ! !mkcolg ! ! ! ! ! ! ! !Joined: 30 Jun 2004 ! !Posts: 4616 ! !Location: The Portland Group Inc. ! !PostPosted: Tue Dec 14, 2004 2:03 pm Post subject: Reply with quote! !Hello, ! ! ! ! ! !At this time we don't plan on supporting REAL*16. This is due to the ! !lack of hardware support and the extreme performance penalty of ! !software emulation. Of course, if we see more demand then we'll ! !reconsider. ! ! ! !Thanks, ! !Mat ! ! ! ![. . .]" ! !-----------------------------------------------------------------------! Similarly from HTTP://StackOverflow.com/questions/2799684/x86-64-long-double-precision : |__________________________________________________________________| |"[. . .] | | | |x86-64 precision is the same as regular x86. Extended double is 80| |bits, using the x87 ISA, with 6 padding bytes added. There is no | |128-bit FP hardware. | | | |[. . .] | | | |answered May 10 '10 at 0:16 | |Potatoswatter | |[. . .] | | | |[. . .]" | |__________________________________________________________________|