From ... Path: archiver1.google.com!news1.google.com!newsfeed.stanford.edu!newsfeeds.belnet.be!news.belnet.be!ossa.telenet-ops.be!nmaster.kpnqwest.net!nreader1.kpnqwest.net.POSTED!not-for-mail Newsgroups: comp.lang.lisp Subject: Re: CMUCL18d on Alpha? References: <3CBA8472.48774F5C@ilt.fhg.de> <3CBBE1E6.93F85F44@ilt.fhg.de> <3CBBF4AC.39CD4A4C@kfunigraz.ac.at> <3CBE88D1.6A17BCE1@ilt.fhg.de> <3CBFBF03.31766207@ilt.fhg.de> <87g01r384r.fsf@nkapi.internal> <3228232604375936@naggum.net> <87k7r31mn5.fsf@nkapi.internal> Mail-Copies-To: never From: Erik Naggum Message-ID: <3228242118692057@naggum.net> Organization: Naggum Software, Oslo, Norway Lines: 25 User-Agent: Gnus/5.09 (Gnus v5.9.0) Emacs/21.2 MIME-Version: 1.0 Content-Type: text/plain; charset=us-ascii Date: Fri, 19 Apr 2002 21:55:19 GMT X-Complaints-To: newsmaster@KPNQwest.no X-Trace: nreader1.kpnqwest.net 1019253319 193.71.199.50 (Fri, 19 Apr 2002 23:55:19 MET DST) NNTP-Posting-Date: Fri, 19 Apr 2002 23:55:19 MET DST Xref: archiver1.google.com comp.lang.lisp:32054 * Bulent Murtezaoglu | Now I am not even sure the 53 bits IEEE double gives you can be used to | hold the conversions of A and B above and not cause you to lose precision | in the addition. This is why most reasonable implementations of floating-point hardware offer much more internal precision, so that intermediate results do not introduce lots of precision-related errors. If, as a compiler writer, you are very good at this stuff, you use _only_ the longer internal forms for as long as you possibly can, storing only single- or double-float numbers when you have to. Common Lisp supports a long-float format that should be mapped to this longer form, which is usually an 80-bit format instead of the 64-bit double-float format used by default. (_Computing_ with single-float these days is just plain nuts, even though it may make sense to store values of that type.) It appears reasonable to expect that double-floats will read and print correctly when the underlying representation used for the computation is such a long-float, but then it would be wasteful to believe the same for the (internal) long-floats. /// -- In a fight against something, the fight has value, victory has none. In a fight for something, the fight is a loss, victory merely relief. Post with compassion: http://home.chello.no/~xyzzy/kitten.jpg