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From: Mikko <mikko.levanto@iki.fi>
Newsgroups: comp.theory
Subject: Re: Anyone with sufficient knowledge of C knows that DD specifies non-terminating behavior to HHH
Date: Tue, 25 Feb 2025 16:59:00 +0200
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On 2025-02-24 23:36:04 +0000, olcott said:

> On 2/24/2025 2:47 AM, Mikko wrote:
>> On 2025-02-23 17:44:25 +0000, olcott said:
>> 
>>> On 2/23/2025 4:59 AM, Mikko wrote:
>>>> On 2025-02-22 16:11:31 +0000, olcott said:
>>>> 
>>>>> On 2/22/2025 3:04 AM, Mikko wrote:
>>>>>> On 2025-02-21 22:35:16 +0000, olcott said:
>>>>>> 
>>>>>>> On 2/21/2025 2:18 AM, Mikko wrote:
>>>>>>>> On 2025-02-20 21:31:44 +0000, olcott said:
>>>>>>>> 
>>>>>>>>> On 2/20/2025 2:38 AM, Mikko wrote:
>>>>>>>>>> On 2025-02-20 00:31:33 +0000, olcott said:
>>>>>>>>>> 
>>>>>>>>>>> On 2/19/2025 3:01 AM, Mikko wrote:
>>>>>>>>>>>> On 2025-02-18 11:26:25 +0000, olcott said:
>>>>>>>>>>>> 
>>>>>>>>>>>>> On 2/18/2025 3:24 AM, Mikko wrote:
>>>>>>>>>>>>>> On 2025-02-17 09:05:42 +0000, Fred. Zwarts said:
>>>>>>>>>>>>>> 
>>>>>>>>>>>>>>> Op 16.feb.2025 om 23:51 schreef olcott:
>>>>>>>>>>>>>>>> On 2/16/2025 4:30 PM, joes wrote:
>>>>>>>>>>>>>>>>> Am Sun, 16 Feb 2025 15:58:14 -0600 schrieb olcott:
>>>>>>>>>>>>>>>>>> On 2/16/2025 2:02 PM, joes wrote:
>>>>>>>>>>>>>>>>>>> Am Sun, 16 Feb 2025 13:24:14 -0600 schrieb olcott:
>>>>>>>>>>>>>>>>>>>> On 2/16/2025 10:35 AM, joes wrote:
>>>>>>>>>>>>>>>>>>>>> Am Sun, 16 Feb 2025 06:51:12 -0600 schrieb olcott:
>>>>>>>>>>>>>>>>>>>>>> On 2/15/2025 2:49 AM, Mikko wrote:
>>>>>>>>>>>>>>>>>>>>>>> On 2025-02-14 12:40:04 +0000, olcott said:
>>>>>>>>>>>>>>>>>>>>>>>> On 2/14/2025 2:58 AM, Mikko wrote:
>>>>>>>>>>>>>>>>>>>>>>>>> On 2025-02-14 00:07:23 +0000, olcott said:
>>>>>>>>>>>>>>>>>>>>>>>>>> On 2/13/2025 3:20 AM, Mikko wrote:
>>>>>>>>>>>>>>>>>>>>>>>>>>> On 2025-02-13 04:21:34 +0000, olcott said:
>>>>>>>>>>>>>>>>>>>>>>>>>>>> On 2/12/2025 4:04 AM, Mikko wrote:
>>>>>>>>>>>>>>>>>>>>>>>>>>>>> On 2025-02-11 14:41:38 +0000, olcott said:
>>>>>>>>>>>>>>>>> 
>>>>>>>>>>>>>>>>>>>>>>>> DD  correctly simulated by HHH cannot possibly terminate normally.
>>>>>>>>>>>>>>>>>>>>>>> 
>>>>>>>>>>>>>>>>>>>>>>> That claim has already shown to be false. Nothing above shows that
>>>>>>>>>>>>>>>>>>>>>>> HHH does not return 0. If it does DD also returns 0.
>>>>>>>>>>>>>>>>>>>>>> When we are referring to the above DD simulated by HHH and not
>>>>>>>>>>>>>>>>>>>>>> trying to get away with changing the subject to some other DD
>>>>>>>>>>>>>>>>>>>>>> somewhere else
>>>>>>>>>>>>>>>>>>>>> such as one that calls a non-aborting version of HHH
>>>>>>>>>>>>>>>>>>>>> 
>>>>>>>>>>>>>>>>>>>>>> then anyone with sufficient knowledge of C programming knows that no
>>>>>>>>>>>>>>>>>>>>>> instance of DD shown above simulated by any corresponding instance
>>>>>>>>>>>>>>>>>>>>>> of HHH can possibly terminate normally.
>>>>>>>>>>>>>>>>>>>>> Well, then that corresponding (by what?) HHH isn’t a decider.
>>>>>>>>>>>>>>>>>>>> I am focusing on the isomorphic notion of a termination analyzer.
>>>>>>>>>>>>>>>>>>> (There are other deciders that are not termination analysers.)
>>>>>>>>>>>>>>>>>>> 
>>>>>>>>>>>>>>>>>>>> A simulating termination analyzer correctly rejects any input that
>>>>>>>>>>>>>>>>>>>> must be aborted to prevent its own non-termination.
>>>>>>>>>>>>>>>>>>> Yes, in particular itself is not such an input, because we *know* that
>>>>>>>>>>>>>>>>>>> it halts, because it is a decider. You can’t have your cake and eat it
>>>>>>>>>>>>>>>>>>> too.
>>>>>>>>>>>>>>>>>> I am not even using the confusing term "halts".
>>>>>>>>>>>>>>>>>> Instead I am using in its place "terminates normally".
>>>>>>>>>>>>>>>>>> DD correctly simulated by HHH cannot possibly terminate normally.
>>>>>>>>>>>>>>>>> What’s confusing about „halts”? I find it clearer as it does not imply
>>>>>>>>>>>>>>>>> an ambiguous „abnormal termination”. How does HHH simulate DD
>>>>>>>>>>>>>>>>> terminating abnormally, then? Why doesn’t it terminate abnormally
>>>>>>>>>>>>>>>>> itself?
>>>>>>>>>>>>>>>>> You can substitute the term: the input DD to HHH does not need to be
>>>>>>>>>>>>>>>>> aborted, because the simulated decider terminates.
>>>>>>>>>>>>>>>>> 
>>>>>>>>>>>>>>>> 
>>>>>>>>>>>>>>>> typedef void (*ptr)();
>>>>>>>>>>>>>>>> int HHH(ptr P);
>>>>>>>>>>>>>>>> 
>>>>>>>>>>>>>>>> int DD()
>>>>>>>>>>>>>>>> {
>>>>>>>>>>>>>>>>   int Halt_Status = HHH(DD);
>>>>>>>>>>>>>>>>   if (Halt_Status)
>>>>>>>>>>>>>>>>     HERE: goto HERE;
>>>>>>>>>>>>>>>>   return Halt_Status;
>>>>>>>>>>>>>>>> }
>>>>>>>>>>>>>>>> 
>>>>>>>>>>>>>>>> int main()
>>>>>>>>>>>>>>>> {
>>>>>>>>>>>>>>>>   HHH(DD);
>>>>>>>>>>>>>>>> }
>>>>>>>>>>>>>>>> 
>>>>>>>>>>>>>>>> Every simulated input that must be aborted to
>>>>>>>>>>>>>>>> prevent the non-termination of HHH is stipulated
>>>>>>>>>>>>>>>> to be correctly rejected by HHH as non-terminating.
>>>>>>>>>>>>>>>> 
>>>>>>>>>>>>>>> A very strange and invalid stipulation.
>>>>>>>>>>>>>> 
>>>>>>>>>>>>>> It merely means that the words do not have their ordinary meaning.
>>>>>>>>>> 
>>>>>>>>>> Those two comments are not discussed below.
>>>>>>>>>> 
>>>>>>>>>>>>> Unless HHH(DD) aborts its simulation of DD itself cannot possibly 
>>>>>>>>>>>>> terminate normally.
>>>>>>>>>>>> 
>>>>>>>>>>>> That cannot be determined without examination of HHH, which is not in the
>>>>>>>>>>>> scope of OP.
>>>>>>>>>>> 
>>>>>>>>>>> I have given everyone here all of the complete source
>>>>>>>>>>> code for a few years
>>>>>>>>>> 
>>>>>>>>>> True but irrelevant. OP did not specify that HHH means that particular
>>>>>>>>>> code.
>>>>>>>>>> 
>>>>>>>>> 
>>>>>>>>> Every post that I have been talking about for two or
>>>>>>>>> more years has referred to variations of that same code.
>>>>>>>> 
>>>>>>>> OP had a pointer of that code but didn's state that that code is a part
>>>>>>>> of the problem. OP did not spacify any range for variation.
>>>>>>>> 
>>>>>>> 
>>>>>>> I have only been talking about variations of the same code
>>>>>>> as HHH(DD) for two years. Do you understand that one sentence?
>>>>>> 
>>>>>> I understnd the sentence except the word "variations". What is the
>>>>>> range of "variations"?
>>>>>> 
>>>>> 
>>>>> Good you are being completely reasonable.
>>>>> There are at least two algorithms the current
>>>>> one that was also the original one is easiest to
>>>>> understand. This algorithm essentially spots the
>>>>> equivalent of infinite recursion. The code provides
>>>>> all of the details.
>>>>> 
>>>>>> Anyway OP did not specify that HHH is restricted to those "variations".
>>>>>> Another undefined word of OP is "cannot". About a person it may mean
>>>>>> that one does not do what one wants to do but a program does not want.
>>>>>> 
>>>>> 
>>>>> HHH is exactly as specified. Assuming otherwise is silly.
>>>> 
>>>> The words "as specified" when nothing is specified are not a good use
>>>> of the language.
>>>> 
>>> 
>>> _DD()
>>> [00002133] 55         push ebp      ; housekeeping
>>> [00002134] 8bec       mov ebp,esp   ; housekeeping
>>> [00002136] 51         push ecx      ; make space for local
>>> [00002137] 6833210000 push 00002133 ; push DD
>>> [0000213c] e882f4ffff call 000015c3 ; call HHH(DD)
>>> [00002141] 83c404     add esp,+04
>>> [00002144] 8945fc     mov [ebp-04],eax
>>> [00002147] 837dfc00   cmp dword [ebp-04],+00
>>> [0000214b] 7402       jz 0000214f
>>> [0000214d] ebfe       jmp 0000214d
>>> [0000214f] 8b45fc     mov eax,[ebp-04]
>>> [00002152] 8be5       mov esp,ebp
>>> [00002154] 5d         pop ebp
>>> [00002155] c3         ret
>>> Size in bytes:(0035) [00002155]
>>> 
>>> When DD is correctly simulated by HHH according to the behavior
>>> that the above machine code specifies then the call from DD
>>> to HHH(DD) cannot possibly return making it impossible for DD
>>> emulated by HHH to terminate normally.
>> 
>> That code does not specify whether HHH ever returns or what value
>> HHH returns if it does.
>> 
> 
> When HHH is known to emulate the above code with an x86
> emulator THEN

Although OP says that HHH simulates it does not specify what is
simulated.

> the above machine code specifies then the call from DD
> to HHH(DD) cannot possibly return making it impossible for DD
> emulated by HHH to terminate normally.

That cannot be inferred from anything OP shows. Anyway, it does not
matter what HHH should return if it does not return it.

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