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Path: ...!weretis.net!feeder9.news.weretis.net!news.quux.org!eternal-september.org!feeder3.eternal-september.org!news.eternal-september.org!eternal-september.org!.POSTED!not-for-mail From: dbush <dbush.mobile@gmail.com> Newsgroups: comp.theory Subject: Re: Halting Problem: What Constitutes Pathological Input Date: Tue, 6 May 2025 16:53:19 -0400 Organization: A noiseless patient Spider Lines: 124 Message-ID: <vvdsru$3lapa$7@dont-email.me> References: <GE4SP.47558$VBab.42930@fx08.ams4> <vvamqc$o6v5$4@dont-email.me> <vvan7q$o4v0$1@dont-email.me> <ts5SP.113145$_Npd.41800@fx01.ams4> <vvat0g$vtiu$1@dont-email.me> <vvatf3$o4v0$3@dont-email.me> <vvaut0$vtiu$4@dont-email.me> <vvav6o$o4v0$4@dont-email.me> <vvb329$15u5b$1@dont-email.me> <vvb37g$1451r$1@dont-email.me> <vvb43f$15u5b$4@dont-email.me> <vvb8fm$1a9jr$1@dont-email.me> <vvc4ok$26dgq$1@dont-email.me> <vvcubb$2sk4a$2@dont-email.me> <vvdlu8$3j2mn$1@dont-email.me> <vvdof1$3lapa$2@dont-email.me> <vvdrn6$3n3t4$2@dont-email.me> <vvds7a$3lapa$4@dont-email.me> <vvdsl3$3n3t4$6@dont-email.me> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Injection-Date: Tue, 06 May 2025 22:53:19 +0200 (CEST) Injection-Info: dont-email.me; posting-host="80f1b624b2b67f0b720d14d0d7fce339"; logging-data="3844906"; mail-complaints-to="abuse@eternal-september.org"; posting-account="U2FsdGVkX19fEU8FkmFV5adxLgARJOM8" User-Agent: Mozilla Thunderbird Cancel-Lock: sha1:CN2MvEFAgn9Lz/GfRs9Jhfid41U= Content-Language: en-US In-Reply-To: <vvdsl3$3n3t4$6@dont-email.me> Bytes: 6256 On 5/6/2025 4:49 PM, olcott wrote: > On 5/6/2025 3:42 PM, dbush wrote: >> On 5/6/2025 4:33 PM, olcott wrote: >>> On 5/6/2025 2:38 PM, dbush wrote: >>>> On 5/6/2025 2:55 PM, olcott wrote: >>>>> On 5/6/2025 7:12 AM, dbush wrote: >>>>>> On 5/6/2025 12:55 AM, olcott wrote: >>>>>>> On 5/5/2025 3:53 PM, Richard Heathfield wrote: >>>>>>>> On 05/05/2025 20:38, olcott wrote: >>>>>>>>> On 5/5/2025 2:23 PM, Richard Heathfield wrote: >>>>>>>>>> On 05/05/2025 20:20, olcott wrote: >>>>>>>>>>> Is "halts" the correct answer for H to return? NO >>>>>>>>>>> Is "does not halt" the correct answer for H to return? NO >>>>>>>>>>> Both Boolean return values are the wrong answer >>>>>>>>>> >>>>>>>>>> Or to put it another way, the answer is undecidable, QED. >>>>>>>>>> >>>>>>>>>> See? You got there in the end. >>>>>>>>>> >>>>>>>>> >>>>>>>>> Is this sentence true or false: "What time is it?" >>>>>>>> >>>>>>>> 20:45GMT, give or take. >>>>>>>> >>>>>>>>> is also "undecidable" because it is not a proposition >>>>>>>>> having a truth value. >>>>>>>> >>>>>>>> No, it's computable and therefore decidable. Your computer is >>>>>>>> perfectly capable of displaying its interpretation of the time. >>>>>>>> >>>>>>>>> Is this sentence true or false: "This sentence is untrue." >>>>>>>>> is also "undecidable" because it is not a semantically sound >>>>>>>>> proposition having a truth value. >>>>>>>> >>>>>>>> But we know that it halts at the full stop. >>>>>>>> >>>>>>>>> Can Carol correctly answer “no” to this (yes/no) question? >>>>>>>> >>>>>>>> You have, I see, learned that not all yes/no questions are >>>>>>>> decidable. Well done! You're coming along nicely. >>>>>>>> >>>>>>>>> Both Yes and No are the wrong answer proving that >>>>>>>>> the question is incorrect when the context of who >>>>>>>>> is asked is understood to be a linguistically required >>>>>>>>> aspect of the full meaning of the question. >>>>>>>> >>>>>>>> The question is grammatically and syntactically unremarkable. I >>>>>>>> see no grounds for claiming that it's 'incorrect'. It's just >>>>>>>> undecidable. >>>>>>>> >>>>>>>> You appear to be trying to overturn the Halting Problem by >>>>>>>> claiming that Turing somehow cheated. You're entitled to hold >>>>>>>> that opinion, but it's not one that will gain any traction with >>>>>>>> peer reviewers when you try to publish. >>>>>>>> >>>>>>> >>>>>>> *EVERYONE IGNORES THIS* >>>>>>> It is very simple the mapping from inputs to outputs >>>>>>> must have a well defined sequence of steps. >>>>>>> >>>>>> >>>>>> FALSE!!! >>>>>> >>>>>> There is no requirement that mappings have steps to compute them. >>>>>> >>>>> >>>>> The requirement is that >>>> >>>> Assuming that an algorithm exists that can compute the following >>>> mapping: >>>> >>>> >>>> Given any algorithm (i.e. a fixed immutable sequence of >>>> instructions) X described as <X> with input Y: >>>> >>>> A solution to the halting problem is an algorithm H that computes >>>> the following mapping: >>>> >>>> (<X>,Y) maps to 1 if and only if X(Y) halts when executed directly >>>> (<X>,Y) maps to 0 if and only if X(Y) does not halt when executed >>>> directly >>>> >>>> >>>>> OUTPUTS must correspond >>>>> to INPUTS. This requires that outputs must be >>>>> derived from INPUTS. >>>> >>>> And when a contradiction is reached that proves the above assumption >>>> false, as Linz and others have proved, and you have *explicitly* >>>> admitted is correct. >>> >>> As I already said Linz is only correct when the halting >>> problem proof is construed as >> >> After assuming that an algorithm exists to map the halting function >> >>> having an input that can >>> actually do the opposite of whatever value the termination >>> analyzer returns. Since this is false, >> >> That proves the above assumption false, as Linz and others have proved >> and as you have *explicitly* agreed is correct. >> > > The fundamental basic assumption of all of the halting > problem proofs is that An algorithm exists that can compute the following mapping: Given any algorithm (i.e. a fixed immutable sequence of instructions) X described as <X> with input Y: A solution to the halting problem is an algorithm H that computes the following mapping: (<X>,Y) maps to 1 if and only if X(Y) halts when executed directly (<X>,Y) maps to 0 if and only if X(Y) does not halt when executed directly > THIS ASSUMPTION IS FALSE. As Linz and others have proved, and as you have *explicitly* agreed is correct.