Re: Michael Sipser of MIT validates the notion of a simulating halt decider

On 2025-05-13 13:58:09 +0000, olcott said:

On 5/13/2025 2:46 AM, Mikko wrote:

On 2025-05-12 17:14:03 +0000, olcott said:
 

On 10/12/2022 6:49 PM, Keith Thompson wrote:

olcott <polcott2@gmail.com> writes:

On 10/12/2022 5:37 PM, Richard Damon wrote:

On 10/12/22 11:08 AM, olcott wrote:

Professor Michael Sipser of MIT said that this verbatim paragraph
looks correct:

 <quoted email to professor Sipser>
Here is what I would like to say:
 Professor Michael Sipser of MIT said that this verbatim paragraph
looks correct:
 If H does correctly determine that its correct simulation
of D would never stop  running unless aborted, would it be
correct for H to abort this simulation and report that D
specifies a non-halting sequence of configurations?
 This validates the idea of a simulating halt decider referenced in
this paper.
 Rebutting the Sipser Halting Problem Proof
https://www.researchgate.net/ publication/364302709_Rebutting_the_Sipser_Halting_Problem_Proof
 Professor Sipser has not had the time to carefully review this paper
presented to him.
</quoted email to professor Sipser>
 <quoted reply from professor Sipser>
Looks ok.  Thanks for checking.
</quoted reply from professor Sipser>
 

IF I drop by and ask him face to face, will he confirm this?

 Yes.

 Would Professor Sipser agree that you have refuted his halting problem
proof?
 If I understand this correctly, it does not support the idea that a
general "simulating halt decider" can actually exist.
 In the above, let D be a program that may or may not halt, and let H be
an observer who attempts to determine whether or not D halts.
Concretely, let D be this C program or equivalent:
 int main(void) { while (1) { } }
 and I'll be H.  I can observe D.  I can simulate it until I get bored,
which won't take long (one iteration, two iterations, three iterations,
zzzzzzzzz).  I can, while simulating it, conclude that it will never
halt, abort the simulation, and report that it never halts.  It wouldn't
be difficult to automate the process in a way that works for this simple
case.

 My scope is to prove that the "impossible"
input to all the halting problem proofs <is>
decidable.

 As it is provably impossible it is not possible. The nearest you can hope
is to construct an oracle that can do what a Turing machine cannot do. It
would not be easy, just not yet proven imposssible.

 Not at all. No one ever bothered to notice that
the contradictory part is unreachable code because
the counter-example input gets stuck in recursive
simulation. HHH simply sees this repeating pattern
and rejects DD.

As that does not identify any error in any proof it does not matter
whether that is noticed or not. What is soundly proven impossible
is impossible.
--
Mikko