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From: Richard Damon <richard@damon-family.org>
Newsgroups: comp.theory
Subject: Re: How do simulating termination analyzers work? ---Truth Maker
 Maximalism FULL_TRACE
Date: Sun, 13 Jul 2025 21:33:00 -0400
Organization: i2pn2 (i2pn.org)
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On 7/13/25 4:43 PM, olcott wrote:
> On 7/7/2025 9:07 AM, Alan Mackenzie wrote:
>> olcott <polcott333@gmail.com> wrote:
>>> On 7/6/2025 4:23 PM, Alan Mackenzie wrote:
>>>> olcott <polcott333@gmail.com> wrote:
>>>>> On 7/6/2025 12:52 PM, Alan Mackenzie wrote:
>>>>>> olcott <polcott333@gmail.com> wrote:
>>>>>>> On 7/6/2025 11:02 AM, Alan Mackenzie wrote:
>>
>>>> [ .... ]
>>
>>>>>>> int DD()
>>>>>>> {
>>>>>>>      int Halt_Status = HHH(DD);
>>>>>>>      if (Halt_Status)
>>>>>>>        HERE: goto HERE;
>>>>>>>      return Halt_Status;
>>>>>>> }
>>
>>>>>>> Then you should know that DD simulated by HHH
>>>>>>> according to the semantics of the C programming
>>>>>>> language cannot possibly reach its own "return"
>>>>>>> statement final halt state.
>>
>>>>>> An argument like this is at such a low level of abstraction as to 
>>>>>> be near
>>>>>> valuless.
>>
>>>>> It is really weird that you are calling a 100% complete
>>>>> concrete specification "a low level of abstraction".
>>>>> That HHH(DD) correctly determines that DD simulated by
>>>>> HHH cannot possibly halt is a proven fact.
>>
>>>> A complete concrete specification would necessarily include a 
>>>> description
>>>> of what you mean by "simulation".
>>
>>> I specifically mean that this x86 machine code
>> [ .... ]
>>> Is emulated by an x86 emulator named HHH.
>>
>> That's no adequate description.  To make it so, you'd have to say what
>> you mean by an "x86 emulator".  The name you give it is irrelevant
>>
>>>>   But my point was that rather than
>>>> sticking to the abstract nature of the proof, you're chipping tiny 
>>>> pieces
>>>> out of it and dealing with those.  The proof you claim to refute has no
>>>> notion of simulation, for example; it doesn't need it.
>>
>>
>>> *Not at all there are two pieces*
>>> (1) HHH(DD) does correctly determine that its input
>>>      specifies non halting behavior.
>>> (2) The directly executed DD() does not contradict this.
>>
>> The word "correctly" is fully redundant there.
>>
>> The proof does not state whether the constructed function returns true or
>> false, i.e. whether it specifies non halting behaviour. 
> 
> The proof is purported to prove THAT DD is an undecidable
> input for HHH. This is its counter example refuting the
> claim that a universal halt decider can exist.
> 
> 
> 

But since your DD by your own admission is a category error for a halt 
decider, as you have specifically stated it isn't a program as the input 
doesn't include the code of the specific HHH that it calls, you proof is 
just invalid.

Sorry, all you proved is that you don't know what you are talking about.