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From: olcott <polcott2@gmail.com>
Newsgroups: comp.theory,sci.logic
Subject: Re: Can an abort decider be defined that cannot be fooled by any
 pathological input?
Date: Mon, 25 Mar 2024 19:11:09 -0500
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On 3/25/2024 6:47 PM, Richard Damon wrote:
> On 3/25/24 1:33 PM, olcott wrote:
>> On 3/25/2024 11:16 AM, Fred. Zwarts wrote:
>>> Op 25.mrt.2024 om 17:04 schreef olcott:
>>>> On 3/25/2024 10:48 AM, Fred. Zwarts wrote:
>>>>> Op 25.mrt.2024 om 16:17 schreef olcott:
>>>>>> On 3/24/2024 3:51 AM, Fred. Zwarts wrote:
>>>>>>> Op 24.mrt.2024 om 05:55 schreef olcott:
>>>>>>>> Can an abort decider be defined that cannot be fooled by any 
>>>>>>>> pathological input?
>>>>>>>>
>>>>>>>> 01 int D(ptr x)  // ptr is pointer to int function
>>>>>>>> 02 {
>>>>>>>> 03   int Halt_Status = H(x, x);
>>>>>>>> 04   if (Halt_Status)
>>>>>>>> 05     HERE: goto HERE;
>>>>>>>> 06   return Halt_Status;
>>>>>>>> 07 }
>>>>>>>> 08
>>>>>>>> 09 void main()
>>>>>>>> 10 {
>>>>>>>> 11   H(D,D);
>>>>>>>> 12 }
>>>>>>>>
>>>>>>>> Of all of the elements of the set of H(D,D) where H simulates its
>>>>>>>> input there are matched pairs of otherwise identical elements that
>>>>>>>> only differ by whether they abort their simulation or not.
>>>>>>>>
>>>>>>>> The half of these that don't abort are incorrect because all 
>>>>>>>> deciders
>>>>>>>> must halt. This makes the other half correct about the abort/no 
>>>>>>>> abort
>>>>>>>> decision.
>>>>>>>
>>>>>>> No. The other, aborting, half is just wrong, because it aborts 
>>>>>>> when it is not needed. So, the half that aborts is wrong and it 
>>>>>>> may be argued that it is better to not abort something that halts 
>>>>>>> on its own and that 
>>>>>>
>>>>>> At least two software engineers with masters degrees in computer 
>>>>>> science
>>>>>> disagree.
>>>>>
>>>>> Two is not many, considering that with Google for any invalid idea 
>>>>> it is easy to find a several people with a master degree supporting 
>>>>> it.
>>>>>
>>>>>> Exactly what are you software engineering skills?
>>>>>
>>>>> I have been professionally programming since 1986 in several 
>>>>> languages. (Non professionally I started programming in 1975). 
>>>>> Since about 1990 I programmed in C and since about 2000 in C++.
>>>>>
>>>>>
>>>>>> I have been a professional C++ software engineer since Y2K.
>>>>>
>>>>> I'm sorry to hear that olcott has been so smart, but now he does 
>>>>> not even sees what even a beginner sees.
>>>>
>>>> Can D correctly simulated by H terminate normally?
>>>> 01 int D(ptr x)  // ptr is pointer to int function
>>>> 02 {
>>>> 03   int Halt_Status = H(x, x);
>>>> 04   if (Halt_Status)
>>>> 05     HERE: goto HERE;
>>>> 06   return Halt_Status;
>>>> 07 }
>>>> 08
>>>> 09 void main()
>>>> 10 {
>>>> 11   H(D,D);
>>>> 12 }
>>>>
>>>> *Execution Trace*
>>>> Line 11: main() invokes H(D,D);
>>>>
>>>> *keeps repeating* (unless aborted)
>>>> Line 03: simulated D(D) invokes simulated H(D,D) that simulates D(D)
>>>
>>> Even a beginner sees that, if the H that aborts is chosen, simulated 
>>> H(D,D) aborts and returns false (unless aborted). So simulated D 
>>> halts (unless aborted).
>>>
>>
>> I am estimating that you must be fibbing about your programming skill.
>> The D simulated by any implementation of H (that aborts or does not
>> abort its simulation) shown above cannot possibly reach its own line 04
>> also shown above.
>>
> 
> But that isn't the question.
> 

*That <is> the abort decision question*

> The question is does that machine described by the input Halt when run, 
> or, alternatively, does its correct simulation (not just by H) run 
> forever (and thus needs to be aborted)?
> 

Since you know that H(D,D) must abort its simulation to prevent its
own infinite execution I don't understand why you would lie about it.

I really want to get on to the next step and see if any input can
fool an abort decider into making the wrong abort decision.

Perhaps you already know that you are not up to this challenge?

> Correct simulation refering to a simulation of the EXACT input given to 
> H, that calls the H that you claim to be giving the correct answer (and 
> not the "correct simulator")

-- 
Copyright 2024 Olcott "Talent hits a target no one else can hit; Genius
hits a target no one else can see." Arthur Schopenhauer