Path: utzoo!utgpu!news-server.csri.toronto.edu!cs.utexas.edu!swrinde!zaphod.mps.ohio-state.edu!ncar!gatech!uflorida!haven!adm!cmcl2!kramden.acf.nyu.edu!brnstnd From: brnstnd@kramden.acf.nyu.edu (Dan Bernstein) Newsgroups: comp.lang.misc Subject: Re: Array references cannot be made optimal Message-ID: <12809:Nov1604:07:0490@kramden.acf.nyu.edu> Date: 16 Nov 90 04:07:04 GMT References: <5785:Nov1519:19:5390@kramden.acf.nyu.edu> <36480@nigel.ee.udel.edu> Organization: IR Lines: 26 In article <36480@nigel.ee.udel.edu> new@ee.udel.edu (Darren New) writes: > In article <5785:Nov1519:19:5390@kramden.acf.nyu.edu> brnstnd@kramden.acf.nyu.edu (Dan Bernstein) writes: > >See, this is what I mean about computer scientists. The computational > >model I work with is realistic---it's just my mental picture of what can > >be coded on lots of real machines. As I said before, it's finite. It has > >very, very little to do with a Turing machine. > But the program you write to do the testing you describe requires some memory. Did you read the original description? The first setup I described has two computers, side by side, one running twice as fast as the other. Cache chips---which already do almost all the necessary work---handle the housekeeping. There is no memory loss. The programs work as usual. If your machine is multiprocessing, then it's better to have two processes running side by side than to duplicate the hardware. This does imply some memory use---but in such an environment you can't assume a fixed memory size anyway. > For any given size machine, there will be a value for X where the program > will not halt when you test it but will halt if you run it alone. An "almost > right" solution to the halting problem may be useful, Your objections are based upon the supposed change in the computer's configuration. Hence they are moot. ---Dan