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From: olcott <polcott333@gmail.com>
Newsgroups: comp.theory
Subject: Re: D correctly simulated by pure function H cannot possibly reach
 its, own line 06
Date: Sat, 25 May 2024 16:27:07 -0500
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On 5/25/2024 4:09 PM, Alan Mackenzie wrote:
> [ Followup-To: set ]
> 
> In comp.theory olcott <polcott333@gmail.com> wrote:
> 
> [ .... ]
> 
>> Not at all. I simply utterly reject the dishonest dodge
>> of the strawman deception change-the-subject rebuttal.
> 
>> 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 pair
>> was being referred to.
> 
>> *Correct Simulation Defined*
>>     This is provided because many reviewers had a different notion of
>>     correct simulation that diverges from this notion.
> 
>>     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.
> 
> Having simulated at least one x86 instruction, what does a correct
> simulator then do?  This isn't made clear.  I'm assuming it must return
> an integer, as its C specification says.
> 

D correctly simulated by pure function H means that H correctly emulates
1 to N of the machine language instructions of D with an x86 emulator
and this involves 0 to M recursive emulations of H emulating itself
emulating D.

Because H is a pure function we know that H halts and returns some
value. For simplicity we will say that this value is the meaningless 56.

>>     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.
> 
> Not if the simulation is "correct"; suppose the simulation emulates just
> one instruction of D.  Supposing it then returns 0 (somewhat extending
> your definition of a "correct simulator").  The execution trace will then
> be somewhat different from what you've outlined above.
> 

I rephrased it to be more clear.
Thanks for your review.

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

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