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

On 5/24/24 4:01 PM, olcott wrote:

On 5/24/2024 12:25 PM, Richard Damon wrote:

On 5/24/24 1:10 PM, olcott wrote:

On 5/24/2024 2:37 AM, Fred. Zwarts wrote:

Op 23.mei.2024 om 19:04 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 pair
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.
>
    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.
>

>
Of course this depends very much on the exact meaning of 'correct simulation', or 'correctly emulating'.

>
Not when these are defined above.
>

E.g., take the call to H(p, p). If H recognizes that it is a call to a H with the same algorithm as is it using itself, and it knows that itself returns a certain integer value K, than it can be argued that it is a correct emulation to substitute the call to H with this integer value K, which is assigned to Halt_Status. Then the simulation of D can proceed to line 04.
What we need is an exact definition of 'correct simulation', in this

>
No, you simply need to pay complete attention to the fact that this
has already been provided.
>
I have been over the exact same issue with dozens and dozen of people
though hundreds and hundreds of messages over two years.

>
Excpet that we have two contradictory definitions present,

>
Yes you have a definition of simulation where the x86 machine
language of D is simulated incorrectly or in the wrong order.

 Nope. The UTM definition still simulates EVERY x86 machine language instruction of D simulated correctly in the exact order. The added requirement is that we look at a simulation that is never aborted.