Relay-Version: version B 2.10 5/3/83; site utzoo.UUCP Posting-Version: version B 2.10.2 9/18/84; site oddjob.UUCP Path: utzoo!watmath!clyde!burl!ulysses!mhuxr!mhuxt!houxm!ihnp4!oddjob!matt From: matt@oddjob.UUCP (Matt Crawford) Newsgroups: net.physics Subject: Re: Quickly Computing Quarks (Science News, VOL. 128) Message-ID: <945@oddjob.UUCP> Date: Sat, 24-Aug-85 17:39:37 EDT Article-I.D.: oddjob.945 Posted: Sat Aug 24 17:39:37 1985 Date-Received: Sun, 25-Aug-85 13:27:56 EDT References: <509@sri-arpa.ARPA> <230@geowhiz.UUCP> Reply-To: matt@oddjob.UUCP (Matt Crawford) Organization: U. Chicago, Astronomy & Astrophysics Lines: 23 In article <230@geowhiz.UUCP> karsh@geowhiz.UUCP (Bruce Karsh) writes: >Does anybody know how you would go about retaining significant digits >in a computation like this? If you figure there there will be about >10**9 round off errors per second accumulating for one year, there must >be some plans for designing the calculations to be *EXTREMELY* >insensitive to round off problems. I have done calculations of this sort (on a much smaller scale), and round-off errors do not accumulate. The system being simulated is represented by discrete parts and and then each part is repeatedly altered at random to any of its allowable states with the probability of each state dependent on the energy of that state and a parameter which plays the role of temperature. As the parameter is gradually reduced, the lowest energy state of the system should be discovered. IBM has used this technique to lay out chips on a circuit board. The "energy" of a given configuration is a count of how many wire crossings or how much wire length is needed to connect the chips. _____________________________________________________ Matt University crawford@anl-mcs.arpa Crawford of Chicago ihnp4!oddjob!matt