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From: Ben Bacarisse <ben@bsb.me.uk>
Newsgroups: comp.theory
Subject: Re: Every sufficiently competent C programmer knows
Date: Thu, 13 Mar 2025 15:44:34 +0000
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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.

-- 
Ben.