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From: olcott <polcott333@gmail.com>
Newsgroups: comp.theory,sci.logic
Subject: Can D simulated by H terminate normally?
Date: Sat, 27 Apr 2024 19:17:48 -0500
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Can D simulated by H terminate normally?

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