Path: ...!eternal-september.org!feeder3.eternal-september.org!news.eternal-september.org!eternal-september.org!.POSTED!not-for-mail From: olcott Newsgroups: comp.theory Subject: Re: Incorrect requirements --- Computing the mapping from the input to HHH(DD) Date: Fri, 9 May 2025 23:27:06 -0500 Organization: A noiseless patient Spider Lines: 102 Message-ID: References: <87msbmeo3b.fsf@nosuchdomain.example.com> <87ecwyekg2.fsf@nosuchdomain.example.com> <87bjs2cyj6.fsf@nosuchdomain.example.com> <87msblcg60.fsf@nosuchdomain.example.com> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Injection-Date: Sat, 10 May 2025 06:27:07 +0200 (CEST) Injection-Info: dont-email.me; posting-host="7be348abb5bc2ec0a70724586a3ca680"; logging-data="3520393"; mail-complaints-to="abuse@eternal-september.org"; posting-account="U2FsdGVkX1/P/GCIuJ8M3bNNwDC4fobI" User-Agent: Mozilla Thunderbird Cancel-Lock: sha1:n9HS0Luvn/m7BmTFO78KFDJtJso= X-Antivirus-Status: Clean Content-Language: en-US X-Antivirus: Norton (VPS 250509-6, 5/9/2025), Outbound message In-Reply-To: Bytes: 6430 On 5/9/2025 10:29 PM, Richard Damon wrote: > On 5/9/25 11:17 PM, olcott wrote: >> On 5/9/2025 10:12 PM, Keith Thompson wrote: >>> Mike Terry writes: >>>> On 09/05/2025 03:23, Keith Thompson wrote: >>>>> Richard Damon writes: >>>>>> On 5/8/25 7:53 PM, olcott wrote: >>>>> [...] >>>>>>> void DDD() >>>>>>> { >>>>>>>      HHH(DDD); >>>>>>>      return; >>>>>>> } >>>>>>> We don't need to look at any of my code for me >>>>>>> to totally prove my point. For example when >>>>>>> the above DDD is correctly simulated by HHH >>>>>>> this simulated DDD cannot possibly reach its own >>>>>>> "return" instruction. >>>>>> >>>>>> And thus not correctly simulatd. >>>>>> >>>>>> Sorry, there is no "OS Exemption" to correct simulaiton;. >>>>> Perhaps I've missed something.  I don't see anything in the above >>>>> that >>>>> implies that HHH does not correctly simulate DDD.  Richard, you've >>>>> read >>>>> far more of olcott's posts than I have, so perhaps you can clarify. >>>>> If we assume that HHH correctly simulates DDD, then the above code >>>>> is >>>>> equivalent to: >>>>>       void DDD() >>>>>       { >>>>>         DDD(); >>>>>         return; >>>>>       } >>>>> which is a trivial case of infinite recursion.  As far as I can >>>>> tell, >>>>> assuming that DDD() is actually called at some point, neither the >>>>> outer execution of DDD nor the nested (simulated) execution of DDD >>>>> can reach the return statement.  Infinite recursion might either >>>>> cause a stack overflow and a probable program crash, or an unending >>>>> loop if the compiler implements tail call optimization. >>>>> I see no contradiction, just an uninteresting case of infinite >>>>> recursion, something that's well understood by anyone with a >>>>> reasonable level of programming experience.  (And it has nothing to >>>>> do with the halting problem as far as I can tell, though of course >>>>> olcott has discussed the halting problem elsewhere.) >>>>> Richard, what am I missing? >>>> >>>> Depends on what you've picked up on. >>>> >>>> Do you get that HHH's simulation is a /partial/ simulation?  HHH is >>>> free to simulate a few x86 instructions of DDD, and then simply >>>> abandon the simulation and return.  Since such a simulation is >>>> obviously NOT equivalent to a direct call to DDD, and above you argue >>>> that it is, I'd say you've missed that. >>> >>> I have not read the vast majority of olcott's post here.  For most >>> of the recent discussion I had with him, there was no mention of >>> partial simulation.  olcott finally said something about simulating >>> just a few instructions, but at the same time he finally indicated >>> that understanding his arguments would require an understanding of >>> x86 machine and/or assembly language.  That's when I bailed out. >>> >>> A "correct simulation", as I understand the term, would require fully >>> simulate the execution of DDD.  If DDD never halts, its simulation never >>> halts.  olcott seems to think that he's found a way around this that's >>> relevant to the Halting Problem, but I withdrew before getting to that >>> point. >>> >> >> It only need be a correct simulation until HHH sees the >> repeating pattern that would cause itself to never terminate. > > Right, but that pattern needs to be based on the fact that HHH is a > program that can abort its simulation, and in fact WILL. > >> >> The best selling author of theory of computation textbooks >> agreed that I could quote his agreement with my words. >> >> >>      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. >> >> >> > *simulated D would never stop running unless aborted* means determining what would happen if this H never aborted. -- Copyright 2024 Olcott "Talent hits a target no one else can hit; Genius hits a target no one else can see." Arthur Schopenhauer