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From: "Fred. Zwarts" <F.Zwarts@HetNet.nl>
Newsgroups: comp.theory
Subject: Re: Indirect Reference Changes the Behavior of DDD() relative to DDD
 emulated by HHH
Date: Sat, 31 Aug 2024 17:15:54 +0200
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Op 31.aug.2024 om 14:50 schreef olcott:
> On 8/30/2024 8:31 AM, Mikko wrote:
>> On 2024-08-29 14:04:05 +0000, olcott said:
>>
>>> On 8/29/2024 3:00 AM, Mikko wrote:
>>>> On 2024-08-28 11:46:58 +0000, olcott said:
>>>>
>>>>> On 8/28/2024 2:33 AM, Mikko wrote:
>>>>>> On 2024-08-27 13:04:26 +0000, olcott said:
>>>>>>
>>>>>>> On 8/27/2024 12:45 AM, joes wrote:
>>>>>>>> Am Mon, 26 Aug 2024 18:03:41 -0500 schrieb 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:
>>>>>>>>
>>>>>>>>>>>> We don't really know what context Sipser was given.  I got 
>>>>>>>>>>>> in touch
>>>>>>>>>>>> at the time so I do 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".
>>>>>>>>
>>>>>>>>>> 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!
>>>>>>>> Is this an accurate phrasing, pete?
>>>>>>>
>>>>>>> Deciders never compute the mapping of the computation
>>>>>>> that they themselves are contained within.
>>>>>>
>>>>>> Why not? A decider always either accepts or rejects its input.
>>>>>
>>>>> The computation that they themselves are contained within cannot
>>>>> possibly be an input.
>>>>
>>>> What would prevent that if the input language permits computations?
>>>>
>>>
>>> When a TM takes its own machine description as input
>>> this is not always that same behavior as the direct
>>> execution of the machine. It is not the same because
>>> it is one level of indirect reference away.
>>
>> Now you contradict what you said above. You said that deciders never
>> conpute the mapping of the computation they themselves are contained
>> within. 
> 
> Although deciders cannot possibly see their own behavior
> other people can see this behavior.
> 
>> Now you are saying that they do in a way that might not be
>> as expected.
>>
> 
> If is a verified fact that DDD has different behavior
> before it is aborted in the same way that people are
> hungry before they eat.

No, the behaviour specified by the finite string does not change when a 
simulator decides to do the simulation only halfway. It is just an 
incorrect simulation.

> 
> than the behavior of DDD after it has been aborted,
> people are not hungry after they eat.

If two people are hungry and one of them eats, the other one is still 
hungry and needs to eat. It is stupid to say that they are no longer 
hungry because they have eaten.
Similarly the simulating HHH is not longer hungry, but the simulated HHH 
still is hungry and has not yet eaten.

> 
> The direct execution of DDD includes the behavior
> of the emulated DDD after it has been aborted.

And the simulator should also simulate until it sees the behaviour of 
after the simulated HHH has aborted its simulator. But, of course, it 
can't do that.
HHH cannot possibly simulate itself correctly up to the end.
I told you so many times. When will you finally understand it?

> 
> The emulation of DDD includes the behavior of DDD
> before it has been aborted.

Which makes it an incomplete simulation, which does not tell anything 
about how a correct simulation would continue. Any prediction is just a 
wild guess. An incorrect guess in this case.

> 
> The behavior of infinite recursion is different
> before its second recursive call has been aborted
> than after this second call has been aborted.

Dreaming again of an infinite recursion? Stop dreaming. HHH is 
programmed to prevent an infinite recursion. That holds for both the 
simulating and the simulated HHH.
Dreams are no substitute for facts.
That the simulating HHH fails to see that the simulated HHH would also 
prevent the infinite recursion, is just a programming error and not a 
justification for deciding that it sees an infinite recursion.
HHH cannot possibly simulate itself correctly up to the end.