| Deutsch English Français Italiano |
|
<v3po03$v133$5@dont-email.me> View for Bookmarking (what is this?) Look up another Usenet article |
Path: ...!eternal-september.org!feeder3.eternal-september.org!news.eternal-september.org!.POSTED!not-for-mail From: olcott <polcott333@gmail.com> Newsgroups: comp.theory Subject: Re: Why does Olcott care about simulation, anyway? --- Mikes Review Date: Wed, 5 Jun 2024 08:08:19 -0500 Organization: A noiseless patient Spider Lines: 208 Message-ID: <v3po03$v133$5@dont-email.me> References: <v3j20v$3gm10$2@dont-email.me> <J_CdnTaA96jxpcD7nZ2dnZfqnPudnZ2d@brightview.co.uk> <v3jei1$3o3a7$1@dont-email.me> <0xqdnd8ktrnsc8D7nZ2dnZfqnPqdnZ2d@brightview.co.uk> <v3l002$5d3$1@dont-email.me> <lZadnYLpbtuB7cP7nZ2dnZfqn_udnZ2d@brightview.co.uk> <v3lrm2$4h2j$1@dont-email.me> <v3lsd6$2uv04$17@i2pn2.org> <v3ltij$8gjv$3@dont-email.me> <v3lvc6$2uv03$6@i2pn2.org> <v3nhuh$gatu$4@dont-email.me> <v3p2ss$s8bi$1@dont-email.me> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Injection-Date: Wed, 05 Jun 2024 15:08:20 +0200 (CEST) Injection-Info: dont-email.me; posting-host="dbcb5a2e000d59c1dda264f94a647a93"; logging-data="1016931"; mail-complaints-to="abuse@eternal-september.org"; posting-account="U2FsdGVkX1/aPxeNG+IGmAFtpv+PyD2o" User-Agent: Mozilla Thunderbird Cancel-Lock: sha1:R/ibskGaT10wWQRZbMmkOrad5xk= In-Reply-To: <v3p2ss$s8bi$1@dont-email.me> Content-Language: en-US Bytes: 11341 On 6/5/2024 2:08 AM, Mikko wrote: > On 2024-06-04 17:12:49 +0000, olcott said: > >> On 6/3/2024 9:49 PM, Richard Damon wrote: >>> On 6/3/24 10:18 PM, olcott wrote: >>>> On 6/3/2024 8:59 PM, Richard Damon wrote: >>>>> On 6/3/24 9:46 PM, olcott wrote: >>>>>> On 6/3/2024 8:38 PM, Mike Terry wrote: >>>>>>> On 03/06/2024 18:54, olcott wrote: >>>>>>>> On 6/3/2024 11:25 AM, Mike Terry wrote: >>>>>>>>> On 03/06/2024 04:50, olcott wrote: >>>>>>>>>> On 6/2/2024 10:28 PM, Mike Terry wrote: >>>>>>>>>>> On 03/06/2024 01:16, immibis wrote: >>>>>>>>>>>> The halting problem says you can't find a Turing machine >>>>>>>>>>>> that tells whether executing each other Turing machine will >>>>>>>>>>>> halt. Simulation has nothing to do with the question. >>>>>>>>>>> >>>>>>>>>>> Background: >>>>>>>>>>> >>>>>>>>>>> PO claims to have refuted the common HP proof, e.g. as >>>>>>>>>>> covered in the Linz book "An Introduction to Formal Languages >>>>>>>>>>> and Automata". PO occasionally posts a link to a PDF >>>>>>>>>>> containing an extract of the 5 or so pages of the book >>>>>>>>>>> containing the proof, but I expect you have access to this or >>>>>>>>>>> equivalent. >>>>>>>>>>> >>>>>>>>>>> In a nutshell, the proof goes: >>>>>>>>>>> - Suppose H is a TM Halt decider that decides for any input >>>>>>>>>>> <P><I> whether >>>>>>>>>>> TM P run with input I on its input tape halts. >>>>>>>>>>> [<P> is the string representation of the actual TM P, and >>>>>>>>>>> <I> is the string representation of input tape I] >>>>>>>>>>> - Construct from H a new TM H^ using the mechanical process >>>>>>>>>>> described in the proof. >>>>>>>>>>> If H exists, then its corresponding H^ also exists. >>>>>>>>>>> - Show that the construction of H^ ensures that: >>>>>>>>>>> - if H decides input <H^><H^> (representing H^ running >>>>>>>>>>> with input <H^>) halts, >>>>>>>>>>> then that implies that H^ running with input <H^> >>>>>>>>>>> never halts >>>>>>>>>>> - if H decides input <H^><H^> never halts, >>>>>>>>>>> then that implies H^ running with input <H^> halts >>>>>>>>>>> I.e. either way, H decides the specific input <H^><H^> >>>>>>>>>>> incorrectly, contradicting >>>>>>>>>>> the initial assumption that H is a halt decider. >>>>>>>>>>> - So no halt decider exists. (Every proposed halt decider >>>>>>>>>>> decides at least one input case >>>>>>>>>>> incorrectly, viz input <H^><H^>.) >>>>>>>>>>> >>>>>>>>>>> PO basically claimed he had a fully coded TM H, which >>>>>>>>>>> CORRECTLY decides its "nemesis" input <H^><H^>, contradicting >>>>>>>>>>> the logic of the Linz proof [without pointing out any actual >>>>>>>>>>> mistake in the Linz proof]. Given most people here >>>>>>>>>>> understand the Linz proof well enough to see it is basically >>>>>>>>>>> sound, people were sceptical! >>>>>>>>>>> >>>>>>>>>>> It turned out PO was lying about the fully coded TM, and in >>>>>>>>>>> fact what he actually had was the idea behind a C program >>>>>>>>>>> which would "prove" his idea. A couple of years(?) later he >>>>>>>>>>> actually completed his C program and his x86utm.exe which >>>>>>>>>>> would simulate the x86 code of his H and H^ to "prove" his >>>>>>>>>>> claim. His equivalent of Linz H is his C function H or HH, >>>>>>>>>>> and his equivalent of Linz H^ is his D or DD respectively. >>>>>>>>>>> (They run under x86utm.exe and are not Windows/Unix >>>>>>>>>>> executables.) >>>>>>>>>>> >>>>>>>>>>> H/HH use PARTIAL simulation of their input to decide >>>>>>>>>>> halting/non-halting, returning >>>>>>>>>>> 0 or 1 to communicate their decision. As you correctly point >>>>>>>>>>> out, to the HP proof simulation is quite irrelevant, being >>>>>>>>>>> just one kind of data manipulation that H may perform on its >>>>>>>>>>> input string <P><I> before it decides the halting status. So >>>>>>>>>>> the Linz HP proof covers such H, no problem. >>>>>>>>>>> [I put PARTIAL in caps, just because there seems to be some >>>>>>>>>>> confusion in recent threads as to what PO means by >>>>>>>>>>> "simulation". He doesn't say it explicitly, despite >>>>>>>>>>> suggestions to this effect, but he always means what might be >>>>>>>>>>> called /partial/ simulation.] >>>>>>>>>>> >>>>>>>>>>> PO believes that by (partially) simulating the computation >>>>>>>>>>> corresponding to the input <P><I> [i.e. calculating the >>>>>>>>>>> successive x86 instruction steps of the computation P(I)] and >>>>>>>>>>> monitoring the progress of virtual x86 state changes (like >>>>>>>>>>> instruction address and op-code and so on) H could spot some >>>>>>>>>>> pattern that reveals whether computation P(I) halts or not. >>>>>>>>>>> At this point in the partial simulation, his H would stop >>>>>>>>>>> simulating (aka "abort" the simulation) and return the >>>>>>>>>>> appropriate halt status for input <P><I>. >>>>>>>>>>> >>>>>>>>>>> Nothing remarkable so far! Clearly a tight-loop in P /can/ >>>>>>>>>>> be detected in this fashion, so /some/ <P><I> inputs /can/ be >>>>>>>>>>> correctly determined like this. The PO claim however is that >>>>>>>>>>> the specific input <H^><H^> is correctly decided by his H. >>>>>>>>>>> In C terms those correspond to H(D,D) correctly returning the >>>>>>>>>>> halt status of computation D(D). [PO would probably dispute >>>>>>>>>>> this, because he doesn't properly understand halting or the >>>>>>>>>>> HP generally, or in fact pretty much /any abstract concept/ ] >>>>>>>>>>> >>>>>>>>>> >>>>>>>>>> Introduction to the Theory of Computation, by Michael Sipser >>>>>>>>>> https://www.amazon.com/Introduction-Theory-Computation-Michael-Sipser/dp/113318779X/ >>>>>>>>>> >>>>>>>>>> On 10/13/2022 11:29:23 AM >>>>>>>>>> MIT Professor Michael Sipser agreed this verbatim paragraph is >>>>>>>>>> correct >>>>>>>>>> (He has neither reviewed nor agreed to anything else in this >>>>>>>>>> paper) >>>>>>>>>> >>>>>>>>>> <Professor Sipser agreed> >>>>>>>>>> If simulating halt decider H correctly simulates its input D >>>>>>>>>> until H >>>>>>>>>> correctly determines that its simulated D would never stop >>>>>>>>>> running >>>>>>>>>> unless aborted then >>>>>>>>>> >>>>>>>>>> H can abort its simulation of D and correctly report that D >>>>>>>>>> specifies a >>>>>>>>>> non-halting sequence of configurations. >>>>>>>>>> </Professor Sipser agreed> >>>>>>>>>> >>>>>>>>>> I have started working on what seem to be some computability >>>>>>>>>> issues >>>>>>>>>> that you pointed out with my HH. I found that they are >>>>>>>>>> isolated to >>>>>>>>>> one single element of HH. Essentially the details of how the >>>>>>>>>> master >>>>>>>>>> UTM directly executed HH passes a portion of its tape to its >>>>>>>>>> slaves. >>>>>>>>>> >>>>>>>>>> Nothing else seems to have any computability issues by the >>>>>>>>>> measure >>>>>>>>>> that I am using. >>>>>>>>>> >>>>>>>>>> Message-ID: <rLmcnQQ3-N_tvH_4nZ2dnZfqnPGdnZ2d@brightview.co.uk> >>>>>>>>>> On 3/1/2024 12:41 PM, Mike Terry wrote: >>>>>>>>>> > >>>>>>>>>> > Obviously a simulator has access to the internal state >>>>>>>>>> > (tape contents etc.) of the simulated machine. No problem >>>>>>>>>> there. >>>>>>>>>> >>>>>>>>>> Because of your above comment it seems that correcting this >>>>>>>>>> tiny computability issue with HH is my best path forward. >>>>>>>>>> >>>>>>>>>> >>>>>>>>>> >>>>>>>>>> >>>>>>>>>> You have given the following a blatantly false review when I >>>>>>>>>> said the same thing another way: >>>>>>>>> >>>>>>>>> I have no idea what you're talking about. I did not write any >>>>>>>>> of what follows below. >>>>>>>>> >>>>>>>>> Also I don't believe I said anything "blatantly false". You're >>>>>>>>> incapable of judging what other people say or are thinking - >>>>>>>>> you're often telling people that they'er lying to you and denying >>>>>>>>> "previously verified facts" etc. but its all rubbish - you're >>>>>>>>> in no position to make such judgements. >>>>>>>>> >>>>>>>>> >>>>>>>>> Mike. >>>>>>>>> >>>>>>>> >>>>>>>> You said that the execution trace that I proved is correct is >>>>>>>> incorrect because you didn't like the way that HH was written. >>>>>>>> You said this without looking at my proof as you are doing >>>>>>>> here again. >>>>>>> >>>>>>> An execution trace that is produced by a program that is >>>>>>> incorrect /proves/ nothing whatsoever. I don't need to look at >>>>>>> your proof, as I was commenting on the value of your program >>>>>>> output AS PROOF. ========== REMAINDER OF ARTICLE TRUNCATED ==========