Re: Halting Problem: What Constitutes Pathological Input

On 2025-05-05 19:27:18 +0000, olcott said:

On 5/5/2025 2:12 PM, dbush wrote:

On 5/5/2025 2:47 PM, olcott wrote:

On 5/5/2025 1:21 PM, dbush wrote:

On 5/5/2025 2:14 PM, olcott wrote:

On 5/5/2025 11:16 AM, dbush wrote:

On 5/5/2025 12:13 PM, Mr Flibble wrote:

On Mon, 05 May 2025 11:58:50 -0400, dbush wrote:
 

On 5/5/2025 11:51 AM, olcott wrote:

On 5/5/2025 10:17 AM, Mr Flibble wrote:

What constitutes halting problem pathological input:
 Input that would cause infinite recursion when using a decider of the
simulating kind.
 Such input forms a category error which results in the halting problem
being ill-formed as currently defined.
 /Flibble

 I prefer to look at it as a counter-example that refutes all of the
halting problem proofs.

 Which start with the assumption that the following mapping is computable
and that (in this case) HHH computes it:
  Given any algorithm (i.e. a fixed immutable sequence of instructions) X
described as <X> with input Y:
 A solution to the halting problem is an algorithm H that computes the
following mapping:
 (<X>,Y) maps to 1 if and only if X(Y) halts when executed directly
(<X>,Y) maps to 0 if and only if X(Y) does not halt when executed
directly
  

int DD()
{
    int Halt_Status = HHH(DD);
    if (Halt_Status)
      HERE: goto HERE;
    return Halt_Status;
}
 https://github.com/plolcott/x86utm
 The x86utm operating system includes fully operational HHH and DD.
https://github.com/plolcott/x86utm/blob/master/Halt7.c
 When HHH computes the mapping from *its input* to the behavior of DD
emulated by HHH this includes HHH emulating itself emulating DD. This
matches the infinite recursion behavior pattern.
 Thus the Halting Problem's "impossible" input is correctly determined
to be non-halting.
 

 Which is a contradiction.  Therefore the assumption that the above
mapping is computable is proven false, as Linz and others have proved
and as you have *explicitly* agreed is correct.

 The category (type) error manifests in all extant halting problem proofs
including Linz.  It is impossible to prove something which is ill- formed
in the first place.
 /Flibble

 All algorithms either halt or do not halt when executed directly. Therefore the problem is not ill formed.
 

 When BOTH Boolean RETURN VALUES are the wrong answer
THEN THE PROBLEM IS ILL-FORMED. Self-contradiction must
be screened out as semantically incorrect.

 In other words, you're claiming that there exists an algorithm, i.e. a fixed immutable sequence of instructions, that neither halts nor does not halt when executed directly.
 

 That is not what I said.

 Then there's no category error, and the halting function is well defined.  It's just that no algorithm can compute it.

 It is insufficiently defined thus causing it
to be incoherently defined.

It is well defined. There are computations that halt and computations that
do not. Nothing else is in the scope of the halting problem.
--
Mikko