Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!execu!sequoia!uudell!bigtex!texsun!newstop!exodus!exodus-bb!khb From: khb@chiba.Eng.Sun.COM (Keith Bierman fpgroup) Newsgroups: comp.sys.sgi Subject: Re: f77 performance under 3.3.1 Message-ID: Date: 1 Nov 90 05:44:54 GMT References: <90Oct29.145239est.57616@ugw.utcs.utoronto.ca> <73658@sgi.sgi.com> Sender: news@exodus.Eng.Sun.COM Organization: Sun MegaSystems Lines: 29 In-reply-to: bron@bronze.wpd.sgi.com's message of 30 Oct 90 18:05:41 GMT .... >"exception" is *not* an error, it is just an exceptional (unusual) Kahan (primary force behind the ieee 754 effort) has a nice slide on this exceptions are not errors. exceptions are not uncommon. ... repeated 50 times.... There are perfectly "normal" applications that do nearly all their computation very close to zero (solving for deviations from an expected value, for example) .... Many vendors (Sun and MIPS included) exclude denomalized support from the hw, and this causes a non-trival class of users to have severe performance problems. Fortunately, most applications which compute things close to zero are perfectly happy with flush to zero arithmetic. Rather than having two librarys, a run-time is handy (in my experience). On suns's that is call abrupt_underflow(). My point in posting is to not allow the spirit of Kahan to be disturbed ... floating point exceptions are not exceptional events ... we should have picked a name sans connotations of frequency. -- ---------------------------------------------------------------- Keith H. Bierman kbierman@Eng.Sun.COM | khb@chiba.Eng.Sun.COM SMI 2550 Garcia 12-33 | (415 336 2648) Mountain View, CA 94043