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-Language: ENGLISH,ASCII-7-bit X-Google-Thread: 103376,18f7f6e041b3e0bf X-Google-Attributes: gid103376,public X-Google-ArrivalTime: 2002-08-19 17:25:13 PST Path: archiver1.google.com!postnews1.google.com!not-for-mail From: dewar@gnat.com (Robert Dewar) Newsgroups: comp.lang.ada Subject: Re: Information Systems Annex (usefulness of Decimal Floats) Date: 19 Aug 2002 17:25:13 -0700 Organization: http://groups.google.com/ Message-ID: <5ee5b646.0208191625.11ebf691@posting.google.com> References: NNTP-Posting-Host: 205.232.38.14 Content-Type: text/plain; charset=ISO-8859-1 Content-Transfer-Encoding: 8bit X-Trace: posting.google.com 1029803113 26810 127.0.0.1 (20 Aug 2002 00:25:13 GMT) X-Complaints-To: groups-abuse@google.com NNTP-Posting-Date: 20 Aug 2002 00:25:13 GMT Xref: archiver1.google.com comp.lang.ada:28230 Date: 2002-08-20T00:25:13+00:00 List-Id: "Robert C. Leif" wrote in message news:... > From: Robert C. Leif > To: Robert Dewar et al. > Decimal fixed point is sufficient only if you have a > common intermediate > reference, such as the Dollar, Euro, or gold. However, > one can get into > a combinatorial catastrophe employing multiple conversion > factors. Sorry, this just seems like FUD. I have written a lot of financial code of some complexity in COBOL, and never run into any requirement like this. And as I pointed out before clearly the COBOL community has not considered this a problem or this facility would have been provided. Remember that fixed-point can always be used for any calculations if you are willing to worry carefully about scaling. > Complex scientific and engineering calculations require a > floating type. I still believe that given the existence > of gigahertz processors, that > there is a benefit in performing calculations in the most > human understandable format, decimal. This is wrong for two reasons. 1. The efficiency hit on modern processors between binary floating-point (IEEE 754) and simulated decimal floating point (IEEE 854) is simply huge. Probably a factor of 200 in practice at least, perhaps more with modern pipelined machines. That means your gigahertz processor is crawling along at the equivalent of 5 megahertz (like the original PC-1), totally hopeless for "complex scientific and engineering calculations". 2. There are no gains in practice over binary floating-point. Yes, it may avoid surprises for naive users, but naive users of floating-point should be banned from doing "complex scientific and engineering calculations" since they will make a complete mess of it. Such applications [I have even more experience in that sphere] require a proper understanding of how floating-point works, and how errors propagate, and there is nothing inherently better about decimal fpt. The one area where decimal fpt has turned out to be an advantage is in hand held calculators, where abysmal performance does not matter at all, and you avoid surprises for naive users :-) Note that once you start talking about "complex scientific and engineering" applications, you have completely shifted the sphere of argument away from the subject material. This has nothing whatever to do with the Information Systems Annex.