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From: "Fred. Zwarts" <F.Zwarts@HetNet.nl>
Newsgroups: comp.theory
Subject: Re: Ben Bacarisse fails understand that deciders COMPUTE THE MAPPING
 FROM INPUTS
Date: Tue, 27 Aug 2024 10:58:53 +0200
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Op 27.aug.2024 om 01:03 schreef olcott:
> On 8/26/2024 7:42 AM, Ben Bacarisse wrote:
>> Mike Terry <news.dead.person.stones@darjeeling.plus.com> writes:
>>
>>> On 23/08/2024 22:07, Ben Bacarisse wrote:
>>>> joes <noreply@example.org> writes:
>>>>
>>>>> Am Wed, 21 Aug 2024 20:55:52 -0500 schrieb olcott:
>>>>
>>>>>> Professor Sipser clearly agreed that an H that does a finite 
>>>>>> simulation
>>>>>> of D is to predict the behavior of an unlimited simulation of D.
>>>>>
>>>>> If the simulator *itself* would not abort. The H called by D is,
>>>>> by construction, the same and *does* abort.
>>>> We don't really know what context Sipser was given.  I got in touch at
>>>> the time so do I know he had enough context to know that PO's ideas 
>>>> were
>>>> "wacky" and that had agreed to what he considered a "minor remark".
>>>> Since PO considers his words finely crafted and key to his so-called
>>>> work I think it's clear that Sipser did not take the "minor remark" he
>>>> agreed to to mean what PO takes it to mean!  My own take if that he
>>>> (Sipser) read it as a general remark about how to determine some cases,
>>>> i.e. that D names an input that H can partially simulate to determine
>>>> it's halting or otherwise.  We all know or could construct some such
>>>> cases.
>>>
>>> Exactly my reading.  It makes Sipser's agreement natural, because it is
>>> both correct [with sensible interpretation of terms], and moreover
>>> describes an obvious strategy that a partial decider might use that can
>>> decide halting for some specific cases.  No need for Sipser to be 
>>> deceptive
>>> or misleading here, when the truth suffices.  (In particular no need to
>>> employ "tricksy" vacuous truth get out clauses just to get PO off his 
>>> back
>>> as some have suggested.)
>>
>> Yes, and it fits with his thinking it a "trivial remark".  Mind you I
>> can't help I feeling really annoyed that a respected academic is having
>> his name repeated dragged into this nonsense by PO.
>>
>> That aside, it's such an odd way to present an argument: "I managed to
>> trick X into saying 'yes' to something vague".  In any reasonable
>> collegiate exchange you'd go back and check: "So even when D is
>> constructed from H, H can return based on what /would/ happen if H did
>> not stop simulating so that H(D,D) == false is correct even though D(D)
>> halts?".  Just imagine what Sipser would say to that!
>>
>> Academic exchange thrives on clarity.  Cranks thrive on smoke and
>> mirrors.
>>
> 
> Try to point to the tiniest lack of clarity in this fully
> specified concrete example.
> 
> void DDD()
> {
>    HHH(DDD);
>    return;
> }
> 
> _DDD()
> [00002172] 55         push ebp      ; housekeeping
> [00002173] 8bec       mov ebp,esp   ; housekeeping
> [00002175] 6872210000 push 00002172 ; push DDD
> [0000217a] e853f4ffff call 000015d2 ; call HHH(DDD)
> [0000217f] 83c404     add esp,+04
> [00002182] 5d         pop ebp
> [00002183] c3         ret
> Size in bytes:(0018) [00002183]
> 
> HHH computes the mapping from DDD to behavior that never reaches
> its "return" statement on the basis of the x86 emulation of DDD
> by HHH according to the semantics of the x86 language.

Only, because the simulation stopped, so that it skipped the halting part.

> 
> For all the  years people said that this simulation is incorrect
> never realizing that they were disagreeing with the semantics
> of the x86 language.

No, all these years you did not realise that the simulation deviated 
from the semantics of the x86 language by skipping the last few 
instructions of a halting program.

        int main() {
          return HHH(main);
        }

Has exactly the same problem, proving that the problem is not DDD, but 
HHH, but you simply ignore it.
HHH cannot possibly simulate itself correctly up to the end.
And it uses an unsound 'special condition' to stop the simulation of a 
halting program, because the programmer is still dreaming of an HHH that 
does not halt.