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=-1.3 required=5.0 tests=BAYES_00,INVALID_MSGID autolearn=no autolearn_force=no version=3.4.4 X-Google-Language: ENGLISH,ASCII-7-bit X-Google-Thread: 107079,c7637cfdf68e766 X-Google-Attributes: gid107079,public X-Google-Thread: f8362,c7637cfdf68e766 X-Google-Attributes: gidf8362,public X-Google-Thread: f43e6,c7637cfdf68e766 X-Google-Attributes: gidf43e6,public X-Google-Thread: 109d8a,c7637cfdf68e766 X-Google-Attributes: gid109d8a,public X-Google-Thread: 103376,c7637cfdf68e766 X-Google-Attributes: gid103376,public From: dewar@merv.cs.nyu.edu (Robert Dewar) Subject: Re: floating point comparison Date: 1997/08/29 Message-ID: #1/1 X-Deja-AN: 268992346 Distribution: inet References: <5tnreu$9ac$1@news.fsu.edu> <5u4eq6$30b$1@news.lth.se> Organization: New York University Newsgroups: comp.lang.ada,sci.math.num-analysis,comp.software-eng,comp.theory,sci.math Date: 1997-08-29T00:00:00+00:00 List-Id: <<<> It is especially difficult for non-native speakers of a language to accurately understand the connotation of words, as opposted to the denotation. Dictionaries tend to concentrate only on the denotation, especially if you just quote the definition -- you can sometimes get a better feel for the connotation by looking through the references in a comprehensive dictionary (really the only one for the English language is the full edition of the OED). The problem with the word error is that, while of course everyone knows its denotation (certainly you don't have to go to a dictionary for that), all native speakers of English also very much no its connotation, which is bad, horrible, something-to-avoid, evil, unacceptable ... i.e. uniformly negative (for a feeling of this connotation have a look at the use of the word error by Mary Baker Eddy, who essentially uses it as a synonym for what other religeons call sin -- now to be fair it is not as negative as sin, and that was MBE's reason for arguing for using the word error instead, but it most assuredly is something to avoid). Of course the phrase "roundoff error" is denotationally appropriate, and is not about to mislead people who understand FPT semantics and numerical analysis. But as this whole thread has made clear, there are a lot of people who (a) want to use fpt, and (b) meet neither of these criteria. FOr such people, the use of the word error is in practice damaging because it suggests there is something wrong with floating-point, and it leads to superstitious mumbo-jumbo like always use Float'Epsilon when comparing any two floating-point quantities, to avoid the dreaded ERROR! As I have repeatedly said, I do not seriously suggest the entire community change its terminology, that is of course impossible, but I am suggesting that by concentrating on the effect of this word, and suggesting that a more neutral word like discrepancy would have been better (note that your dictionary definition would apply almost unchanged to disccrepancy), we might avoid some of this superstition! Please understand that my point here is not technical. I perfectly well understand how fpt works, and have written large numerical codes, properly and carefully analyzed with respect to "error" propagation that are still in wide use. My point is entirely about trying to get people to understand that the use and implementation of floating-point is well defined in computer systems, and does not involve "error" in the informal connotative sense.