Path: ...!eternal-september.org!feeder3.eternal-september.org!news.eternal-september.org!eternal-september.org!.POSTED!not-for-mail From: "Fred. Zwarts" Newsgroups: comp.theory Subject: Re: Incorrect requirements --- Computing the mapping from the input to HHH(DD) Date: Sat, 10 May 2025 10:44:55 +0200 Organization: A noiseless patient Spider Lines: 99 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 10:44:59 +0200 (CEST) Injection-Info: dont-email.me; posting-host="6132ef5c9a5712f5fb4e052234097a74"; logging-data="3603725"; mail-complaints-to="abuse@eternal-september.org"; posting-account="U2FsdGVkX19E0AdEvAj+4LCbqs5Qp3kn" User-Agent: Mozilla Thunderbird Cancel-Lock: sha1:WnsH2Dr6WGlt2/6WnizZH4/7Kk8= Content-Language: nl, en-GB In-Reply-To: Bytes: 6458 Op 10.mei.2025 om 06:27 schreef olcott: > 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. But since D is aborted, this is a vacuous statement. That is what H should take into account.