Path: utzoo!utgpu!news-server.csri.toronto.edu!bonnie.concordia.ca!thunder.mcrcim.mcgill.edu!snorkelwacker.mit.edu!hsdndev!think.com!rpi!dali.cs.montana.edu!uakari.primate.wisc.edu!aplcen!aplcomm!uunet!mcsun!corton!geocub!billaud From: billaud@geocub.UUCP (Michel BILLAUD) Newsgroups: comp.lang.misc Subject: Re: Will this *thread* ever halt? Message-ID: <3441@geocub.UUCP> Date: 17 Jun 91 09:59:38 GMT References: <22012:Jun1205:25:0491@kramden.acf.nyu.edu> <1991Jun12.194212.21395@clipper.ingr.com> <10452.Jun1317.26.4791@kramden.acf.nyu.edu> Organization: GRECO Programmation du CNRS & LaBRI - FRANCE Lines: 43 In article <10452.Jun1317.26.4791@kramden.acf.nyu.edu> brnstnd@kramden.acf.nyu.edu (Dan Bernstein) writes: >In article <1991Jun12.194212.21395@clipper.ingr.com> smryan@clipper.ingr.com (Steven Ryan) writes: >> In article <22012:Jun1205:25:0491@kramden.acf.nyu.edu> brnstnd@kramden.acf.nyu.edu (Dan Bernstein) writes: >> Your conclusion >> therefore only applies to bounded programs. > >No shit. That's what ``for any given *size*'' means: it's a *bound*. >(``Welcome to Mr. Rogers' Neighborhood. Can you say `bound'? B-O-U-N-D. >Bound. Very good, boys and girls. This is a bound.'') > >> You have no proof that unbounded >> programs do not exist. > >Sure I do. Computers have finite memory. To determine halting for an IBM >PC in some state, I need merely hook up another IBM PC and a bit of >extra hardware, and run both machines a bit slower than usual. To >determine halting for a given language environment, the interpreter or >compiler need only duplicate its memory and do a bit of housekeeping. >This is eminently practical. Another point is that there is only a *FINITE*NUMBER* of computers in the universe. As "Computers have finite memory", there exists a computer CM which has more memory than others. "Practically", there will be no computer to run your program to determine halting on that CM. You could object that you may "hook up" several CM with additional hardware : but there is a finite number of networks, and so on. Also we mortals have a limited amount of time, so ... M Billaud -- Michel BILLAUD : billaud@geocub.greco-prog.fr Departement d'Informatique : IUT "A", Universite Bordeaux I : phone W: 56.84.57.92 // 56.84.69.22 33405 Talence (FRANCE) : H: 56.36.65.90 (answering mach.)