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From: olcott <polcott333@gmail.com>
Newsgroups: comp.lang.c++,comp.lang.c
Subject: Re: Can you see that D correctly simulated by H remains stuck in
 recursive simulation?
Date: Sat, 25 May 2024 23:19:17 -0500
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On 5/25/2024 2:32 AM, Fred. Zwarts wrote:
> Op 23.mei.2024 om 18:52 schreef olcott:
>> typedef int (*ptr)();  // ptr is pointer to int function in C
>> 00       int H(ptr p, ptr i);
>> 01       int D(ptr p)
>> 02       {
>> 03         int Halt_Status = H(p, p);
>> 04         if (Halt_Status)
>> 05           HERE: goto HERE;
>> 06         return Halt_Status;
>> 07       }
>> 08
>> 09       int main()
>> 10       {
>> 11         H(D,D);
>> 12         return 0;
>> 13       }
>>
>> The above template refers to an infinite set of H/D pairs where D is
>> correctly simulated by pure function H. This was done because many
>> reviewers used the shell game ploy to endlessly switch which H/D was
>> being referred to.
>>
>> *Correct Simulation Defined*
>> This is provided because every reviewer had a different notion of
>> correct simulation that diverges from this notion.
>>
>> In the above case a simulator is an x86 emulator that correctly emulates
>> at least one of the x86 instructions of D in the order specified by the
>> x86 instructions of D.
>>
>> This may include correctly emulating the x86 instructions of H in the
>> order specified by the x86 instructions of H thus calling H(D,D) in
>> recursive simulation.
>>
>> *Execution Trace*
>> Line 11: main() invokes H(D,D); H(D,D) simulates lines 01, 02, and 03 of
>> D. This invokes H(D,D) again to repeat the process in endless recursive
>> simulation.
>>
> 
> Olcott's own words are that the simulation of D never reaches past line 
> 03. So the lines following line 03 do not play a role and, therefore, 
> can be removed without changing the claim. This leads to:
> 
> typedef int (*ptr)();  // ptr is pointer to int function in C
> 00       int H(ptr p, ptr i);
> 01       int D(ptr p)
> 02       {
> 03         return H(p, p);
> 04       }
> 05
> 06       int main()
> 07       {
> 08         H(D,D);
> 09         return 0;
> 10       }
> 
> 
> What we see is that the only property of D that is used is that it is a 
> parameter duplicator. (Is that why it is called D?). H needs 2 
> parameters, but it can be given only one input parameter, so the 
> parameter duplicator is required to allow H to decide about itself.
> 
> 
> 
> Of the infinite set of H that simulate at least one step, none of them, 
> when simulated by H, halts, because none of them reaches its final 
> state. Olcott's claim is equivalent to the claim of non-halting 
> behaviour of H.
> This means that a simulating halt-decider is a bad idea, because the 
> decider itself does not halt.

Not at all.
    A simulator is an x86 emulator that correctly emulates 1 to N of the
    x86 instructions of D in the order specified by the x86 instructions
    of D. This may include M recursive emulations of H emulating itself
    emulating D.

    This means that D cannot possibly reach its own line 06 and halt
    in any finite steps of correct simulation. H is free to halt at
    any time after these N finite steps of correct simulation.


-- 
Copyright 2024 Olcott "Talent hits a target no one else can hit; Genius
hits a target no one else can see." Arthur Schopenhauer