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From: Mikko <mikko.levanto@iki.fi>
Newsgroups: comp.theory
Subject: Re: D(D) simulated by H cannot possibly reach past its own line 03
Date: Wed, 5 Jun 2024 10:05:19 +0300
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On 2024-06-03 18:09:30 +0000, olcott said:

> On 6/3/2024 9:17 AM, Mikko wrote:
>> On 2024-06-03 12:25:48 +0000, olcott said:
>> 
>>> On 6/3/2024 2:39 AM, Mikko wrote:
>>>> On 2024-06-02 14:50:26 +0000, olcott said:
>>>> 
>>>>> On 6/2/2024 4:50 AM, Fred. Zwarts wrote:
>>>>>> Op 03.mei.2024 om 15:40 schreef olcott:
>>>>>>> 00 int H(ptr x, ptr x)  // ptr is pointer to int function
>>>>>>> 01 int D(ptr x)
>>>>>>> 02 {
>>>>>>> 03   int Halt_Status = H(x, x);
>>>>>>> 04   if (Halt_Status)
>>>>>>> 05     HERE: goto HERE;
>>>>>>> 06   return Halt_Status;
>>>>>>> 07 }
>>>>>>> 08
>>>>>>> 09 void main()
>>>>>>> 10 {
>>>>>>> 11   H(D,D);
>>>>>>> 12 }
>>>>>>> 
>>>>>>> We are examining the behavior of D(D) for every possible H/D pair
>>>>>>> where 1 to N steps of D(D) are simulated by H.
>>>>>>> 
>>>>>>> *Execution Trace*
>>>>>>> Line 11: main() invokes H(D,D) that simulates D(D)
>>>>>>> 
>>>>>>> *keeps repeating* (unless aborted)
>>>>>>> Line 01
>>>>>>> Line 02
>>>>>>> Line 03: simulated D(D) invokes simulated H(D,D) that simulates D(D)
>>>>>>> 
>>>>>>> *Simulation invariant*
>>>>>>> D correctly simulated by H cannot possibly reach past its own line 03.
>>>>>> 
>>>>>> The Linz proof is based on the pathological relation ship that D 
>>>>>> contradicts the result of H. This is expressed in lines 04, 05, 06 of 
>>>>>> D, above.
>>>>>> It is strange that olcott claims that the simulation never sees the 
>>>>>> pathological part of D. He now seems to shift the meaning of 
>>>>>> pathological to the mere fact that D calls H. Lines 04, 05, and 06 are 
>>>>>> completely irrelevant.
>>>>>> In fact, any function that calls H now become pathological.
>>>>>> 
>>>>>> E.G. if we replace D with a function P that only returns its own Halt_Status:
>>>>>> 
>>>>>> 01 int P(ptr x)
>>>>>> 02 {
>>>>>> 03   int Halt_Status = H(x, x);
>>>>>> 04
>>>>>> 05
>>>>>> 06   return Halt_Status;
>>>>>> 07 }
>>>>>> 
>>>>>> Then we would normally expect that, because H is required to halt, P 
>>>>>> would halt as well. But the simulation of P by H does not halt. So, P, 
>>>>>> when it halts, reports that it not halting.
>>>>>> 
>>>>>> The problem here is, that H is unable to simulate itself to its final 
>>>>>> state. That has no relation with the Linz proof, it is a problem of H.
>>>>>> 
>>>>>> So, there is another *Simulation invariant*
>>>>>> H correctly simulated by H cannot possibly reach its own return.
>>>>>> 
>>>>> 
>>>>> Already addressed in another reply.
>>>> 
>>>> Which reply? The one where you said you made a mistake? Or typo?
>>>> 
>>> 
>>> I am not going to answer the same question from multiple people.
>> 
>> Your choice. But you can't keep multiple people from seeing your
>> lack of answer.
>> 
> 
> This is my canned reply that no one has attempted to refute because
> they know it is irrefutable. When we are analyzing x86 code and
> someone disagrees that is like disagreeing that 2 + 3 = 5.

The code has been anylzed by several people so carefully that
any disagreement really is like s like disagreeing that 2 + 3 = 5.
But you disagree anyway:

> DD correctly emulated by any HH that can possibly exist DOES NOT HALT

-- 
Mikko