Article View: comp.lang.fortran
Article #6526Re: Precision of floating point multiply
From: James Giles
Date: Mon, 29 Sep 2003 20:55
Date: Mon, 29 Sep 2003 20:55
24 lines
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2590 bytes
Glen Herrmannsfeldt wrote: ... > What I was saying is that if conversion from single to double did not clear > those bits you would get whatever was left there, possibly from an unrelated > calculation. I believe that would be a bad idea, but some posts by others > seem to indicate that it would be legal Fortran. Someone else posted: > >> Item (6) listed in Section 1.4 of the Fortran standard explicitly >> states that the standard does not specify >> >> (6) The physical properties of the representation of quantities and >> the method of rounding, approximating, or computing numeric >> values on a particular processor. > > The belief is that this statement could include leaving garbage bits in for > low bits. That's probably a correct assessment. In fact, on the system in question, where "rounding" results to single precision is done by truncation, it could be argued that leaving "garbage bits" simulates the missing data! Yes, I have heard appalling reasoning of that kind. -- J. Giles
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X-Google-Language: ENGLISH,ASCII-7-bit X-Google-Thread: fd4af,7830916812112af0 X-Google-Attributes: gidfd4af,public X-Google-Thread: fd705,7830916812112af0 X-Google-Attributes: gidfd705,public X-Google-Thread: 102b75,7830916812112af0 X-Google-Attributes: gid102b75,public X-Google-Thread: 1094ba,7830916812112af0 X-Google-Attributes: gid1094ba,public X-Google-ArrivalTime: 2003-09-29 13:55:51 PST Path: arc1-ca.pugleaf.net!news1.google.com!newsfeed.stanford.edu!logbridge.uoregon.edu!arclight.uoregon.edu!wn13feed!wn11feed!worldnet.att.net!bgtnsc05-news.ops.worldnet.att.net.POSTED!not-for-mail From: "James Giles" <jamesgiles@worldnet.att.net> Newsgroups: comp.lang.fortran,comp.arch,bit.listserv.ibm-main,alt.folklore.computers References: <dG4db.598668$uu5.97984@sccrnsc04> <xrXdb.631209$Ho3.121609@sccrnsc03> <bl9ild$abv$1@pegasus.csx.cam.ac.uk> <Rh0eb.632709$Ho3.121617@sccrnsc03> <bla4k2$nas$1@pegasus.csx.cam.ac.uk> <FR0eb.637973$uu5.101567@sccrnsc04> Subject: Re: Precision of floating point multiply Lines: 26 X-Priority: 3 X-MSMail-Priority: Normal X-Newsreader: Microsoft Outlook Express 6.00.2800.1158 X-MimeOLE: Produced By Microsoft MimeOLE V6.00.2800.1165 Message-ID: <r%0eb.163529$3o3.11771639@bgtnsc05-news.ops.worldnet.att.net> Date: Mon, 29 Sep 2003 20:55:51 GMT NNTP-Posting-Host: 12.83.90.159 X-Complaints-To: abuse@worldnet.att.net X-Trace: bgtnsc05-news.ops.worldnet.att.net 1064868951 12.83.90.159 (Mon, 29 Sep 2003 20:55:51 GMT) NNTP-Posting-Date: Mon, 29 Sep 2003 20:55:51 GMT Organization: AT&T Worldnet