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

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.
--
Mikko