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NNTP-Posting-Date: Mon, 03 Jun 2024 17:36:34 +0000
Subject: Re: Why does Olcott care about simulation, anyway?
Newsgroups: comp.theory,sci.logic
References: <v3j20v$3gm10$2@dont-email.me> <v3jt2s$3qblu$1@dont-email.me>
From: Mike Terry <news.dead.person.stones@darjeeling.plus.com>
Date: Mon, 3 Jun 2024 18:36:34 +0100
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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.

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.

> 
> 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.