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From: olcott <polcott333@gmail.com>
Newsgroups: comp.theory
Subject: Re: Ben fails to understand---- correction
Date: Thu, 4 Jul 2024 09:51:38 -0500
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On 7/4/2024 9:25 AM, olcott wrote:
> On 10/14/2022 7:44 PM, Ben Bacarisse wrote:
>> Python <python@invalid.org> writes:
>>
>> Olcott (annotated):
>>
>>>    If simulating halt decider H correctly simulates its input D until H
>>>    correctly determines that its simulated D would never stop running
>>>
>>>    [comment: as D halts, the simulation is faulty, Pr. Sipser has been
>>>     fooled by Olcott shell game confusion "pretending to simulate" and
>>>     "correctly simulate"]
>>>
>>>    unless aborted then H can abort its simulation of D and correctly
>>>    report that D specifies a non-halting sequence of configurations.
>>
>> I don't think that is the shell game.  PO really /has/ an H (it's
>> trivial to do for this one case) that correctly determines that P(P)
>> *would* never stop running *unless* aborted.  He knows and accepts that
>> P(P) actually does stop.  The wrong answer is justified by what would
>> happen if H (and hence a different P) where not what they actually are.
>>
> 
> <MIT Professor Sipser agreed to ONLY these verbatim words 10/13/2022>
>      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.
> </MIT Professor Sipser agreed to ONLY these verbatim words 10/13/2022>
> 
> It is the case that H must abort its simulation of P to prevent
> its own non-termination. The directly executed P(P) benefits
> from H already having aborted its simulation of P. P correctly
> simulated H cannot reap this benefit proving that it is a different
> sequence of configurations than the directly executed P(P).
> 
>> (I've gone back to his previous names what P is Linz's H^.)
>>
>>> In other words: "if the simulation were right the answer would be
>>> right".
>>
>> I don't think that's the right paraphrase.  He is saying if P were
>> different (built from a non-aborting H) H's answer would be the right
>> one.
>>
>>> But the simulation is not right. D actually halts.
>>
>> But H determines (correctly) that D would not halt if it were not
>> halted.  That much is a truism. 
> 
> Thus H(D,D) must abort the simulation of its input to prevent
> its own non-termination.
> 
>> What's wrong is to pronounce that
>> answer as being correct for the D that does, in fact, stop.
>>
> 

*REPLACED PARAGRAPH*

The directly executed D(D) is executed in a different memory
process. D correctly simulated by H is simulated in its own
separate memory process. The executed D(D) only halts because
D correctly simulated by H was aborted.

A simpler example is show below so that one is not overwhelmed
with too much detail.

> 
> They are not the same instance of D.
> 
> void DDD()
> {
>    HHH(DDD); // creates new process context
> }           // thus not the same DDD as the
>              // one that is directly executed.
> int main()
> {
>    DDD(DDD);
> }
> 
> _DDD()
> [00002163] 55         push ebp
> [00002164] 8bec       mov ebp,esp
> [00002166] 6863210000 push 00002163
> [0000216b] e853f4ffff call 000015c3
> [00002170] 83c404     add esp,+04
> [00002173] 5d         pop ebp
> [00002174] c3         ret
> Size in bytes:(0018) [00002174]
> 
> _main()
> [00002183] 55         push ebp
> [00002184] 8bec       mov ebp,esp
> [00002186] 6863210000 push 00002163 ; push DDD
> [0000218b] e8d3ffffff call 00002163 ; call DDD(DDD)
> [00002190] 83c404     add esp,+04
> [00002193] 33c0       xor eax,eax
> [00002195] 5d         pop ebp
> [00002196] c3         ret
> Size in bytes:(0020) [00002196]
> 
>   machine   stack     stack     machine    assembly
>   address   address   data      code       language
>   ========  ========  ========  =========  =============
> [00002183][001037dd][00000000] 55         push ebp      ; housekeeping
> [00002184][001037dd][00000000] 8bec       mov ebp,esp   ; housekeeping
> [00002186][001037d9][00002163] 6863210000 push 00002163 ; push DDD
> [0000218b][001037d5][00002190] e8d3ffffff call 00002163 ; call HHH(DDD)
> [00002163][001037d1][001037dd] 55         push ebp      ; housekeeping
> [00002164][001037d1][001037dd] 8bec       mov ebp,esp   ; housekeeping
> [00002166][001037cd][00002163] 6863210000 push 00002163 ; push DDD
> [0000216b][001037c9][00002170] e853f4ffff call 000015c3 ; call HHH(DDD)
> 
> New slave_stack at:103881 ; Create new process context
> Begin Local Halt Decider Simulation   Execution Trace Stored at:113889
> [00002163][00113879][0011387d] 55         push ebp      ; housekeeping
> [00002164][00113879][0011387d] 8bec       mov ebp,esp   ; housekeeping
> [00002166][00113875][00002163] 6863210000 push 00002163 ; push DDD
> [0000216b][00113871][00002170] e853f4ffff call 000015c3 ; call HHH(DDD)
> 
> New slave_stack at:14e2a9 ; Create new process context
> [00002163][0015e2a1][0015e2a5] 55         push ebp      ; housekeeping
> [00002164][0015e2a1][0015e2a5] 8bec       mov ebp,esp   ; housekeeping
> [00002166][0015e29d][00002163] 6863210000 push 00002163 ; push DDD
> [0000216b][0015e299][00002170] e853f4ffff call 000015c3 ; call HHH(DDD)
> Local Halt Decider: Infinite Recursion Detected Simulation Stopped
> 
> [00002170][001037d1][001037dd] 83c404     add esp,+04; executed DDD(DDD)
> [00002173][001037d5][00002190] 5d         pop ebp    ; executed DDD(DDD)
> [00002174][001037d9][00002163] c3         ret        ; executed DDD(DDD)
> [00002190][001037dd][00000000] 83c404     add esp,+04
> [00002193][001037dd][00000000] 33c0       xor eax,eax
> [00002195][001037e1][00000018] 5d         pop ebp
> [00002196][001037e5][00000000] c3         ret
> Number of Instructions Executed(10073) == 150 Pages
> 
> 
> 

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