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Failed to connect to MySQL: (1203) User howardkn already has more than 'max_user_connections' active connectionsPath: news.eternal-september.org!eternal-september.org!.POSTED!not-for-mail From: dbush Newsgroups: comp.theory Subject: Re: Every sufficiently competent C programmer knows --- Semantic Property reiterated Date: Thu, 13 Mar 2025 13:16:20 -0400 Organization: A noiseless patient Spider Lines: 140 Message-ID: References: <878qp9gckd.fsf@bsb.me.uk> MIME-Version: 1.0 Content-Type: text/plain; charset=UTF-8; format=flowed Content-Transfer-Encoding: 8bit Injection-Date: Thu, 13 Mar 2025 18:16:20 +0100 (CET) Injection-Info: dont-email.me; posting-host="416957debdcb20d9b566cd00245152da"; logging-data="3561448"; mail-complaints-to="abuse@eternal-september.org"; posting-account="U2FsdGVkX19vQnjWI3P57Lk4RLgkZceY" User-Agent: Mozilla Thunderbird Cancel-Lock: sha1:7SdrvA86rNfT9YwMMPqvvMUJCU4= In-Reply-To: Content-Language: en-US On 3/13/2025 1:10 PM, olcott wrote: > On 3/13/2025 11:44 AM, dbush wrote: >> On 3/13/2025 12:39 PM, olcott wrote: >>> On 3/13/2025 11:12 AM, dbush wrote: >>>> On 3/13/2025 12:09 PM, olcott wrote: >>>>> On 3/13/2025 10:44 AM, Ben Bacarisse wrote: >>>>>> Mike Terry writes: >>>>>> >>>>>>> On 11/03/2025 18:23, Richard Heathfield wrote: >>>>>>>> On 11/03/2025 17:42, Mike Terry wrote: >>>>>>>>> Finally, if you really want to see the actual HHH code, its in the >>>>>>>>> halt7.c file (along with DDD) that PO provides links to from >>>>>>>>> time to >>>>>>>>> time.  However it's not very illuminating due to bugs/design >>>>>>>>> errors/misunderstandings which only serve to obfuscate PO's >>>>>>>>> errors in >>>>>>>>> thinking. >>>>>>>> [I've now seen the code. Oh deary deary me.] >>>>>>> >>>>>>> :) >>>>>>> >>>>>>>> Thank you for a spirited attempt to be cogent - or at least as >>>>>>>> cogent as >>>>>>>> it is possible to be in the circumstances! >>>>>>>> I think PO's first step must be to demonstrate that HHH() correctly >>>>>>>> diagnoses some easy functions, such as these: >>>>>>> >>>>>>> Not really necessary - PO is not trying or claiming to have a (full) >>>>>>> halt decider. >>>>>>> >>>>>>> Originally his claim was that he had a program which worked for the >>>>>>> counter-example TM used in the common (e.g. Linz book) proof. >>>>>> >>>>>> That, of course, depends on the way the wind's blowing.  For >>>>>> example in >>>>>> 2020: >>>>>> >>>>>>    "The non-halting decider that I defined accepts any and all >>>>>>    non-halting inputs and rejects any and all halting inputs." >>>>>> >>>>>> But then he retreated to the "once case" argument again until: >>>>>> >>>>>> Me: "Recent posts have said that you really do claim to have a >>>>>> halting >>>>>>      decider.  Have you extended your claim or was that a >>>>>>      misunderstanding?" >>>>>> >>>>>> PO: "I really do have a halting decider." >>>>>> >>>>>>> ... Such a >>>>>>> program is impossible, as Linz and others prove, so having a >>>>>>> program H and >>>>>>> its corresponding "counter-example" D, such that H correctly >>>>>>> decides D, >>>>>>> would certainly show that the Linz proof is wrong.  His claim was >>>>>>> always >>>>>>> that he had "refuted the HP proof", or sometimes that he had >>>>>>> refuted the HP >>>>>>> theorem itself although he's been told dozens of times that there >>>>>>> are many >>>>>>> alternative proofs for the result. >>>>>> >>>>>> Way back in 2004 he was sure that: >>>>>> >>>>>>    "I have correctly refuted each and every mechanism by which the >>>>>>    [halting theorem] has been proven to be true. I have not shown >>>>>> that >>>>>>    solving the Halting Problem is possible, merely refuted every >>>>>> proof >>>>>>    that it is impossible." >>>>>> >>>>>> I expect a publication anytime.  20 years is just about enough to get >>>>>> all the details right. >>>>>> >>>>>>> [As it turned out, PO's D(D) halted when run under his x86utm >>>>>>> environment, >>>>>>> while H(D,D) which is required to return the halting status of >>>>>>> computation >>>>>>> D(D) returned 0 (=non-halting).  That is exactly what the Linz >>>>>>> proofs >>>>>>> claim!] >>>>>> >>>>>> We must always remember that PO has re-defined what it means for the >>>>>> answer to be correct: >>>>>> >>>>>> Me: "Here's the key question: do you still assert that H(P,P) == >>>>>> false >>>>>>      is the "correct" answer even though P(P) halts?" >>>>>> >>>>>> PO: "Yes that is the correct answer even though P(P) halts." >>>>>> >>>>>> He's been quite clear about it: >>>>>> >>>>>>    "When we make the single change that I suggest the halting problem >>>>>>    ceases to be impossible to solve because this revised question >>>>>> is not >>>>>>    subject to pathological self-reference." >>>>>> >>>>>>    "This transforms an undecidable problem into a decidable problem." >>>>>> >>>>>> I hope you forgive me just chipping in with stuff you know perfectly >>>>>> well, but I thought I'd just give some background as Richard is a new >>>>>> participant and my comments fit better with your post than his. >>>>>> >>>>> >>>>> typedef void (*ptr)(); >>>>> int HHH(ptr P); >>>>> >>>>> int DD() >>>>> { >>>>>    int Halt_Status = HHH(DD); >>>>>    if (Halt_Status) >>>>>      HERE: goto HERE; >>>>>    return Halt_Status; >>>>> } >>>>> >>>>> When N steps of DD are correctly emulated by >>>>> any HHH then each DD cannot possibly reach >>>>> its own final state and terminate normally. >>>>> >>>>> We we recall Rice's Theorem we know that the >>>>> issue to be decided must be based on the semantic >>>>> property that the input finite string specifies. >>>>> >>>> >>>> And the semantic property we care about, which you implicitly agreed >>>> is one, is the property of the directly executed DD. >>> >>> No that is stupidly wrong >> >> Not when it's the direct execution that we care about. >> > > That stupidly ignores that Rice's Theorem requires > that a decider makes its decision on the basis of > a semantic property encoded as a finite string. > It does not, as the semantic property we're interested in that of the direct execution.