Re: Every sufficiently competent C programmer knows --- Semantic Property reiterated

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.