Re: Can you see that D correctly simulated by H remains stuck in recursive simulation?

On 5/25/2024 4:59 AM, Mikko wrote:

On 2024-05-24 16:57:36 +0000, olcott said:
 

On 5/24/2024 10:01 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.

>
The case can be simplified even more (D is not needed):
>

>
We are ONLY asking about whether D correctly simulated by pure function H can possibly reach its own final state at line 06 and halt.
>
Because H is a pure function we know that H halts.

 We don't know that H halts. The OP said the opposite:
 

The above references *pure function* H thus we do know
that the spec *requires* H to halt.
https://en.wikipedia.org/wiki/Pure_function

On 2024-05-23 16:52:21 +0000, olcott said:

*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.

 To repeat in endless recursve simulation makes halting impossible.
Apparently OP's interpretation of "pure function" does not imply
halting.
 

Every H is required to halt and return a value.
To make things simple every H returns the meaningless 56.
It is endless recursive simulation until H halts.
I had to refer to endless recursive simulation so that people
could get the gist of what is going on while hardly paying any
attention at all.
The reason that I had to add that H is a pure function is that
Richard tried to cheat using static local data. Prior to that
there was no requirement that H halt.
--
Copyright 2024 Olcott "Talent hits a target no one else can hit; Genius
hits a target no one else can see." Arthur Schopenhauer