XPost: comp.theory, sci.logic, sci.math

// Simplified Linz Ĥ (Linz:1990:319)
// Strachey(1965) CPL translated to C
void P(u32 x)
{
if (H(x, x))
HERE: goto HERE;
}

This is the assembly language of the above function after it has been translated by the Microsoft C compiler.

_P()
[00000c36](01) 55 push ebp
[00000c37](02) 8bec mov ebp,esp
[00000c39](03) 8b4508 mov eax,[ebp+08] // 2nd Param
[00000c3c](01) 50 push eax
[00000c3d](03) 8b4d08 mov ecx,[ebp+08] // 1st Param
[00000c40](01) 51 push ecx
[00000c41](05) e820fdffff call 00000966 // call H
[00000c46](03) 83c408 add esp,+08
[00000c49](02) 85c0 test eax,eax
[00000c4b](02) 7402 jz 00000c4f
[00000c4d](02) ebfe jmp 00000c4d
[00000c4f](01) 5d pop ebp
[00000c50](01) c3 ret
Size in bytes:(0027) [00000c50]

Begin Local Halt Decider Simulation at Machine Address:c36

machine stack stack machine assembly
address address data code language
======== ======== ======== ========= =============
[00000c36][002117ca][002117ce] 55 push ebp
[00000c37][002117ca][002117ce] 8bec mov ebp,esp
[00000c39][002117ca][002117ce] 8b4508 mov eax,[ebp+08]
[00000c3c][002117c6][00000c36] 50 push eax // push P
[00000c3d][002117c6][00000c36] 8b4d08 mov ecx,[ebp+08]
[00000c40][002117c2][00000c36] 51 push ecx // push P
[00000c41][002117be][00000c46] e820fdffff call 00000966 // call H(P,P)

[00000c36][0025c1f2][0025c1f6] 55 push ebp
[00000c37][0025c1f2][0025c1f6] 8bec mov ebp,esp
[00000c39][0025c1f2][0025c1f6] 8b4508 mov eax,[ebp+08]
[00000c3c][0025c1ee][00000c36] 50 push eax // push P
[00000c3d][0025c1ee][00000c36] 8b4d08 mov ecx,[ebp+08]
[00000c40][0025c1ea][00000c36] 51 push ecx // push P
[00000c41][0025c1e6][00000c46] e820fdffff call 00000966 // call H(P,P)

The above conclusively proves that the pure simulation of the input to
H(P,P) never reaches its final state.

We don't even have to see that the first seven x86 instructions of P
actually repeat. We can know by logical necessity that a pure simulation
of the input to H(P,P) by H never reaches any final state of P on the
basis of the x86 source code of P and the fact that the seventh
instruction of P calls H.

This conclusively proves that H(P,P)==0 is the correct return value for
its input even if H never returns.

If there is no simulating halt decider H in the universe that correctly
decides that its input (P,P) never reaches its final state then the
input (P,P) remains undecidable, none-the-less H(P,P)==0 is still correct.




Strachey, C 1965. An impossible program The Computer Journal, Volume 7,
Issue 4, January 1965, Page 313, https://doi.org/10.1093/comjnl/7.4.313

Linz, Peter 1990. An Introduction to Formal Languages and Automata. Lexington/Toronto: D. C. Heath and Company. (318-320)

Halting problem undecidability and infinitely nested simulation
May 2021 PL Olcott

https://www.researchgate.net/publication/351947980_Halting_problem_undecidability_and_infinitely_nested_simulation




--
Copyright 2021 Pete Olcott

"Great spirits have always encountered violent opposition from mediocre
minds." Einstein

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