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From: olcott <polcott333@gmail.com>
Newsgroups: comp.theory,sci.logic
Subject: Re: Why does Olcott care about simulation, anyway?
Date: Mon, 3 Jun 2024 13:03:44 -0500
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On 6/3/2024 12:36 PM, Mike Terry wrote:
> On 03/06/2024 08:58, Fred. Zwarts wrote:
>> Op 03.jun.2024 om 02:16 schreef immibis:
>>> The halting problem says you can't find a Turing machine that tells 
>>> whether executing each other Turing machine will halt. Simulation has 
>>> nothing to do with the question.
>>
>> Maybe because by using simulation he can shift the attention from the 
>> pathological part of the Linz proof, to another halting problem, 
>> namely that a simulating decider does not halt because it causes 
>> infinite recursion.
> 
> PO's simulating decider does not cause infinite recursion.  That only 
> occurs in the case where the decider performs a FULL simulation of its 
> input, whereas typically for PO his H/HH/... perform PARTIAL 
> simulations, where the decider monitors what is being simulated and 
> breaks off the simulation when a particular condition is observed.
> 

Thanks for affirming that. You are my most technically
competent and honest reviewer.

> So yes, there is recursive simulation, but not /infinite/ recursion 
> since at each level of simulation the simulator is free to just stop 
> simulating at any time.  In practice this means that the outer simulator 
> H will be the one to break out, since it will always be ahead of all the 
> inner simulations of H in how far it has progressed.  This situation is 
> in contrast with direct call recursion, where the outer caller has no 
> control to break the recursion - it only regains control once the inner 
> calls have all returned.
> 
> PO does not properly understand this distinction.
> 

*You can keep ignoring this that does not make it go away*

On 10/13/2022 11:29:23 AM
MIT Professor Michael Sipser agreed this verbatim paragraph is correct
(He has neither reviewed nor agreed to anything else in this paper)

<Professor Sipser agreed>
If simulating halt decider H correctly simulates its input D until H
correctly determines that its simulated D would never stop running
unless aborted then

H can abort its simulation of D and correctly report that D specifies a
non-halting sequence of configurations.
</Professor Sipser agreed>

*You can ignore the above forever, that does not make it away*

>>
>> His own claim that D does not reach the pathological part (after line 
>> 03), displays already that the simulation is unable to process the 
>> pathological part. But the simulation introduces a new halting problem 
>> (recursive simulation), which he thinks is an answer for the original 
>> halting problem.
> 
> You're using PO's phrase "pathological" but that is a bad (misleading) 
> term because it suggests there is something WRONG/BAD (aka sick?) in the 
> situation.  E.g. H processing input which is a description of its own 
> source code.  There is nothing whatsoever wrong with that - it's just 
> that PO gets confused by it and so argues to ban it.  Perhaps there  is 
> an alternative term that doesn't have the deliberate connotation of 
> "sickness".
> 
> Mike.
> 

*Two PhD computer science professors disagree*

E C R Hehner. *Problems with the Halting Problem*, COMPUTING2011 
Symposium on 75 years of Turing Machine and Lambda-Calculus, Karlsruhe 
Germany, invited, 2011 October 20-21; Advances in Computer Science and 
Engineering v.10 n.1 p.31-60, 2013
https://www.cs.toronto.edu/~hehner/PHP.pdf

E C R Hehner. *Objective and Subjective Specifications*
WST Workshop on Termination, Oxford.  2018 July 18.
See https://www.cs.toronto.edu/~hehner/OSS.pdf

Bill Stoddart. *The Halting Paradox*
20 December 2017
https://arxiv.org/abs/1906.05340
arXiv:1906.05340 [cs.LO]

*You can ignore the above forever, that does not make it away*

-- 
Copyright 2024 Olcott "Talent hits a target no one else can hit; Genius
hits a target no one else can see." Arthur Schopenhauer