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On 5/28/2024 11:16 AM, olcott wrote:Right, and to be a "foo" decider, that mapping must map the "foo" mapping, so a Halt Decider must compute the "Halts" funciton, which is True if teh Turing Machine described by the input halts o the other input given.>A decider computes the mapping from finite string inputs to
When Ĥ is applied to ⟨Ĥ⟩
Ĥ.q0 ⟨Ĥ⟩ ⊢* embedded_H ⟨Ĥ⟩ ⟨Ĥ⟩ ⊢* Ĥ.qy ∞
Ĥ.q0 ⟨Ĥ⟩ ⊢* embedded_H ⟨Ĥ⟩ ⟨Ĥ⟩ ⊢* Ĥ.qn
>
*Formalizing the Linz Proof structure*
∃H ∈ Turing_Machines
∀x ∈ Turing_Machines_Descriptions
∀y ∈ Finite_Strings
such that H(x,y) = Halts(x,y)
>
its own accept or reject state.
A decider does not and cannot compute the mapping fromBut it can from the representation of said Turing Machine, which is a finite string.
Turing_Machine inputs to its own accept or reject state.
Halts(x,y) would report on the direct execution of x(y) thus ignoresAnd, if that keeps H from being able to answer, that makes Halts uncomputable, and thus there are no such things as correct Halt Deciders.
the pathological behavior of x correctly simulated by pure function H.
This makes Halts(x,y) an incorrect measure of the correctness of H(x,y).
This is easier to see when we can see every single detail of all ofWRONG!!!
the steps as an x86 execution trace of D correctly simulated by pure
function H.
typedef int (*ptr)(); // ptr is pointer to int function in C
00 int HH(ptr p, ptr i);
01 int DD(ptr p)
02 {
03 int Halt_Status = HH(p, p);
04 if (Halt_Status)
05 HERE: goto HERE;
06 return Halt_Status;
07 }
08
09 int main()
10 {
11 HH(DD,DD);
12 return 0;
13 }
*Begin simulation of DD by HH*
Begin Local Halt Decider Simulation Execution Trace Stored at:113075
[00001c22][00113061][00113065] 55 push ebp
[00001c23][00113061][00113065] 8bec mov ebp,esp
[00001c25][0011305d][00103031] 51 push ecx
[00001c26][0011305d][00103031] 8b4508 mov eax,[ebp+08]
[00001c29][00113059][00001c22] 50 push eax ; push DD
[00001c2a][00113059][00001c22] 8b4d08 mov ecx,[ebp+08]
[00001c2d][00113055][00001c22] 51 push ecx ; push DD
[00001c2e][00113051][00001c33] e80ff7ffff call 00001342 ; call HH
New slave_stack at:14da95
[00001c22][0015da89][0015da8d] 55 push ebpBut that isn't the question for a HALT decicer.
[00001c23][0015da89][0015da8d] 8bec mov ebp,esp
[00001c25][0015da85][0014da59] 51 push ecx
[00001c26][0015da85][0014da59] 8b4508 mov eax,[ebp+08]
[00001c29][0015da81][00001c22] 50 push eax ; push DD
[00001c2a][0015da81][00001c22] 8b4d08 mov ecx,[ebp+08]
[00001c2d][0015da7d][00001c22] 51 push ecx ; push DD
[00001c2e][0015da79][00001c33] e80ff7ffff call 00001342 ; call HH
Local Halt Decider: Recursive Simulation Detected Simulation Stopped
DD correctly simulated by HH cannot possibly reach its own simulated
final state at line 06 in any number of steps including an infinite
number of steps because DD correctly simulated by HH remains stuck in
recursive simulation.
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