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From: dbush <dbush.mobile@gmail.com>
Newsgroups: comp.theory
Subject: Re: Every sufficiently competent C programmer knows --- Semantic
 Property reiterated
Date: Thu, 13 Mar 2025 13:16:20 -0400
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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 <news.dead.person.stones@darjeeling.plus.com> 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.