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Subject: Re: Proof that DDD specifies non-halting behavior --- point by point
Newsgroups: comp.theory
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From: Mike Terry <news.dead.person.stones@darjeeling.plus.com>
Date: Thu, 15 Aug 2024 18:31:27 +0100
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On 15/08/2024 08:00, joes wrote:
> Am Wed, 14 Aug 2024 16:07:43 +0100 schrieb Mike Terry:
>> On 14/08/2024 08:43, joes wrote:
>>> Am Tue, 13 Aug 2024 21:38:07 -0500 schrieb olcott:
>>>> On 8/13/2024 9:29 PM, Richard Damon wrote:
>>>>> On 8/13/24 8:52 PM, olcott wrote:
>>>
>>>>>> A simulation of N instructions of DDD by HHH according to the
>>>>>> semantics of the x86 language is necessarily correct.
>>>>> Nope, it is just the correct PARTIAL emulation of the first N
>>>>> instructions of DDD, and not of all of DDD,
>>>> That is what I said dufuss.
>>> You were trying to label an incomplete/partial/aborted simulation as
>>> correct.
>>>
>>>>>> A correct simulation of N instructions of DDD by HHH is sufficient
>>>>>> to correctly predict the behavior of an unlimited simulation.
>>>>> Nope, if a HHH returns to its caller,
>>>> *Try to show exactly how DDD emulated by HHH returns to its caller*
>>> how *HHH* returns
> 
>>> HHH simulates DDD	enter the matrix
>>>     DDD calls HHH(DDD)	Fred: could be eliminated HHH simulates
> DDD
>>>     second level
>>>       DDD calls HHH(DDD)	recursion detected
>>>     HHH aborts, returns	outside interference DDD halts		
> voila
>>> HHH halts
>>
>> You're misunderstanding the scenario?  If your simulated HHH aborts its
>> simulation [line 5 above],
>> then the outer level H would have aborted its identical simulation
>> earlier.  You know that, right?
> Of course. I made it only to illustrate one step in the paradoxical
> reasoning, as long as we're calling programs that do or don't abort
> the same.

So... it seems that perhaps you agree on this one specific point: that when (some specific) HHH 
partially simulates its associated (specific) DDD, that SIMULATION does not get as far as simulating 
DDD returning?  [Well, it did in your example above, but you seem to have agreed that was logically 
wrong.]

For example, perhaps HHH never aborts so the simulation never terminates, or in the case of PO's HHH 
in halt7.c, HHH aborts its simulation before DDD gets as far as returning.  Either way /the partial 
simulation/ does not proceed to a point where DDD returns...

That's a completely different question from asking whether computation DDD() ever returns, which is 
what a halt decider must decide.  You shouldn't feel that if you agree with the former, that you're 
also agreeing that DDD() never halts, or that "not halting is the right answer for HHH to give for 
input DDD" or any other PO nonsense!

I'd just add that if you do agree with PO on this one specific point, why argue with him about it? 
Just agree and PO will soon move on to some completely ridiculous conclusion that surely would be 
more fun to argue with (assuming you enjoy arguing with PO :)).


Mike.