Path: ...!news.nobody.at!eternal-september.org!feeder3.eternal-september.org!news.eternal-september.org!.POSTED!not-for-mail From: Mikko Newsgroups: comp.theory Subject: Re: Ben Bacarisse fails understand that deciders compute the mapping from inputs Date: Thu, 29 Aug 2024 11:00:37 +0300 Organization: - Lines: 57 Message-ID: References: <431deaa157cdae1cae73a1b24268a61cf8ec2c1c@i2pn2.org> <7a1c569a699e79bfa146affbbae3eac7b91cd263@i2pn2.org> <729cc551062c13875686d266a5453a488058e81c@i2pn2.org> <148bf4dd91f32379a6d81a621fb7ec3fc1e00db0@i2pn2.org> <5591ff08ed8f7b4bdf33813681e156b775efe0ec@i2pn2.org> <878qwn0wyz.fsf@bsb.me.uk> <87le0jzc8f.fsf_-_@bsb.me.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=utf-8; format=flowed Content-Transfer-Encoding: 8bit Injection-Date: Thu, 29 Aug 2024 10:00:37 +0200 (CEST) Injection-Info: dont-email.me; posting-host="2fc2ba747bad9e08201d5742136f75b1"; logging-data="4100129"; mail-complaints-to="abuse@eternal-september.org"; posting-account="U2FsdGVkX1+AtLYKfNSrlkI6Inj8MNzY" User-Agent: Unison/2.2 Cancel-Lock: sha1:Xqt2WtDCMr8rDAa2MefxSjVSLMs= Bytes: 4688 On 2024-08-28 11:46:58 +0000, olcott said: > On 8/28/2024 2:33 AM, Mikko wrote: >> On 2024-08-27 13:04:26 +0000, olcott said: >> >>> On 8/27/2024 12:45 AM, joes wrote: >>>> Am Mon, 26 Aug 2024 18:03:41 -0500 schrieb olcott: >>>>> On 8/26/2024 7:42 AM, Ben Bacarisse wrote: >>>>>> Mike Terry writes: >>>>>>> On 23/08/2024 22:07, Ben Bacarisse wrote: >>>> >>>>>>>> We don't really know what context Sipser was given.  I got in touch >>>>>>>> at the time so I do know he had enough context to know that PO's >>>>>>>> ideas were "wacky" and that had agreed to what he considered a "minor >>>>>>>> remark". Since PO considers his words finely crafted and key to his >>>>>>>> so-called work I think it's clear that Sipser did not take the "minor >>>>>>>> remark" he agreed to to mean what PO takes it to mean!  My own take >>>>>>>> if that he (Sipser) read it as a general remark about how to >>>>>>>> determine some cases, i.e. that D names an input that H can partially >>>>>>>> simulate to determine it's halting or otherwise.  We all know or >>>>>>>> could construct some such cases. >>>>>>> >>>>>>> Exactly my reading.  It makes Sipser's agreement natural, because it >>>>>>> is both correct [with sensible interpretation of terms], and moreover >>>>>>> describes an obvious strategy that a partial decider might use that >>>>>>> can decide halting for some specific cases.  No need for Sipser to be >>>>>>> deceptive or misleading here, when the truth suffices.  (In particular >>>>>>> no need to employ "tricksy" vacuous truth get out clauses just to get >>>>>>> PO off his back as some have suggested.) >>>>>> >>>>>> Yes, and it fits with his thinking it a "trivial remark". >>>> >>>>>> That aside, it's such an odd way to present an argument: "I managed to >>>>>> trick X into saying 'yes' to something vague".  In any reasonable >>>>>> collegiate exchange you'd go back and check: "So even when D is >>>>>> constructed from H, H can return based on what /would/ happen if H did >>>>>> not stop simulating so that H(D,D) == false is correct even though D(D) >>>>>> halts?".  Just imagine what Sipser would say to that! >>>> Is this an accurate phrasing, pete? >>> >>> Deciders never compute the mapping of the computation >>> that they themselves are contained within. >> >> Why not? A decider always either accepts or rejects its input. > > The computation that they themselves are contained within cannot > possibly be an input. What would prevent that if the input language permits computations? For example, every computation can be given to an UTM. That computation may involve a decider X that uses the same input language. What What prevents giving X the same input as the UTM was given? -- Mikko