cgl@t13.Lanl.GOV (Chris Langton) (02/19/91)
angelo@gem.stack.urc.tue.nl writes: > .....because now I have also read 'Winning ways'. > I believe that the Life computer presented there (or rather the > elements to build one) will not work. I hope Callahan's TM will. Can you expand on your doubts about this proof? I have implemented many of the components, and they seem to work as advertised... Where do you think the Life computer presented in Winning Ways breaks down? Cheers! Chris Langton Complex Systems Group MS B213, Theoretical Division Phone: (505) 667-9471 Los Alamos National Laboratory Email: cgl@t13.lanl.gov Los Alamos, New Mexico, USA FAX: (505) 665-3003 87545 <<<<<<<<<<<<<<<<<<<...Its...Its...Its Alive!...>>>>>>>>>>>>>>>>>>>
scott@ferrari.LABS.TEK.COM (Scott Huddleston) (02/26/91)
In article <9102191525.AA08177@t13.lanl.gov> cgl@t13.Lanl.GOV (Chris Langton) writes: >angelo@gem.stack.urc.tue.nl writes: >> .....because now I have also read 'Winning ways'. >> I believe that the Life computer presented there (or rather the >> elements to build one) will not work. I hope Callahan's TM will. > > Can you expand on your doubts about this proof? > > I have implemented many of the components, and they seem to work > as advertised... > > Where do you think the Life computer presented in Winning Ways > breaks down? I'm not angelo@gem.stack.urc.tue.nl, but I have some doubts about the Berlekamp/Conway proof. Here they are. I question their constructions that require creating glider guns at arbitrarily large distances away from a starting configuration. To transport the gliders used as basic components to their destination, their construction sends the gliders up between 2 parallel streams in a kickback reaction. I have a serious doubt and a minor qualm. 1. Look at the arrival timing constraints on the gliders used to build a glider gun. Most can arrive arbitrarily far apart in time, which will work fine with the Berlekamp/Conway transport contruction. But one pair must arrive at a precisely synchronized time, a few ticks behind its predecessor. How can a Berlekamp/Conway 2-stream kickback transport accomplish this? (Comment: The "standard" (i.e. oft-repeated) construction of a glider gun from gliders uses 13 gliders. But 12 suffice (an exercise for the reader). My question applies to both constructions.) 2. (minor qualm) The Berlekamp/Conway 2-stream kickback transport for gliders requires that the streams be synchronized so that they're all ultimately annihilated. How is the information and control to accomplish this handled? Perhaps my doubts only apply to their claim that a self-reproducing life configuration is possible (or one that can reproduce itself arbitrarily far away). I'm perfectly happy with their construction of a memory of arbitrary capacity acheived by moving blocks in and out. -- Scott Huddleston scott@crl.labs.tek.com
ACW@YUKON.SCRC.Symbolics.COM (Allan C. Wechsler) (02/27/91)
It seems that your qualms about the argument in Winning Ways could cause you to doubt the existence of a Constructor but not of a Computer.
ACW@YUKON.SCRC.Symbolics.COM (Allan C. Wechsler) (03/05/91)
Date: Fri, 1 Mar 1991 16:31 EST
From: scott%tekchips.labs.tek.com@RELAY.CS.NET
> It seems that your qualms about the argument in Winning Ways could cause
> you to doubt the existence of a Constructor but not of a Computer.
Right. Do you have any arguments or constructions either suppporting or
refuting their Constructor?
I'd have to refer you to Gosper -- RWG@Symbolics.COM.