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From: olcott <polcott333@gmail.com>
Newsgroups: comp.theory
Subject: Re: Can D simulated by H terminate normally?
Date: Sun, 28 Apr 2024 07:56:36 -0500
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On 4/28/2024 3:23 AM, Mikko wrote:
> On 2024-04-28 00:17:48 +0000, olcott said:
> 
>> Can D simulated by H terminate normally?
> 
> One should not that "D simulated by H" is not the same as
> "simulation of D by H". The message below seems to be more
> about the latter than the former. In any case, it is more
> about the properties of H than about the properties of D.
>  

D specifies what is essentially infinite recursion to H.
Several people agreed that D simulated by H cannot possibly
reach past its own line 03 no matter what H does.

>> The x86utm operating system based on an open source x86 emulator.
>> This system enables one C function to execute another C function
>> in debug step mode. When H simulates D it creates a separate process
>> context for D with its own memory, stack and virtual registers. H
>> is able to simulate D simulating itself, thus the only limit to
>> recursive simulations is RAM.
>>
>> // The following is written in C
>> //
>> 01 typedef int (*ptr)(); // pointer to int function
>> 02 int H(ptr x, ptr y)    // uses x86 emulator to simulate its input
>> 03
>> 04 int D(ptr x)
>> 05 {
>> 06   int Halt_Status = H(x, x);
>> 07   if (Halt_Status)
>> 08     HERE: goto HERE;
>> 09   return Halt_Status;
>> 10 }
>> 11
>> 12 void main()
>> 13 {
>> 14   D(D);
>> 15 }
>>
>> Execution Trace
>> Line 14: main() invokes D(D)
>>
>> keeps repeating (unless aborted)
>> Line 06: simulated D(D) invokes simulated H(D,D) that simulates D(D)
>>
>> Simulation invariant
>> D correctly simulated by H cannot possibly reach its own line 09.
>>
>> Is it dead obvious to everyone here when examining the execution
>> trace of lines 14 and 06 above that D correctly simulated by H cannot
>> possibly terminate normally by reaching its own line 09?
> 
> 

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