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From: Richard Damon <richard@damon-family.org>
Newsgroups: comp.theory
Subject: Re: Every D(D) is correctly simulated by H
Date: Mon, 20 May 2024 20:57:25 -0400
Organization: i2pn2 (i2pn.org)
Message-ID: <v2grhl$1kiah$4@i2pn2.org>
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On 5/20/24 1:58 PM, olcott wrote:
> On 5/20/2024 3:35 AM, Mikko wrote:
>> On 2024-05-19 19:29:01 +0000, olcott said:
>>
>>> On 5/19/2024 2:09 PM, Richard Damon wrote:
>>>> On 5/19/24 2:13 PM, olcott wrote:
>>>>> On 5/19/2024 12:17 PM, Richard Damon wrote:
>>>>>> On 5/19/24 10:03 AM, olcott wrote:
>>>>>>> On 5/19/2024 8:48 AM, Mikko wrote:
>>>>>>>> On 2024-05-19 12:34:08 +0000, olcott said:
>>>>>>>>
>>>>>>>>> On 5/19/2024 2:53 AM, Mikko wrote:
>>>>>>>>>> On 2024-05-18 15:34:36 +0000, James Kuyper said:
>>>>>>>>>>
>>>>>>>>>>> On 5/18/24 09:02, Mikko wrote:
>>>>>>>>>>>> On 2024-05-17 17:14:01 +0000, olcott said:
>>>>>>>>>>>
>>>>>>>>>>> I recommend ignoring olcott - nothing good ever comes from 
>>>>>>>>>>> paying
>>>>>>>>>>> attention to him.
>>>>>>>>>>>
>>>>>>>>>>>>> On 5/17/2024 5:53 AM, Mikko wrote:
>>>>>>>>>>>>>> On 2024-05-16 14:50:19 +0000, olcott said:
>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> On 5/16/2024 5:48 AM, Mikko wrote:
>>>>>>>>>>>>>>>> On 2024-05-15 15:24:57 +0000, olcott said:
>>>>>>>>>>> ...
>>>>>>>>>>>>>>>>> typedef int (*ptr)();  // ptr is pointer to int function
>>>>>>>>>>>>>>>>> 00 int H(ptr x, ptr x);
>>>>>>>>>>>>>>>>> 01 int D(ptr x)
>>>>>>>>>>>>>>>>> 02 {
>>>>>>>>>>>>>>>>> 03   int Halt_Status = H(x, x);
>>>>>>>>>>>>>>>>> 04   if (Halt_Status)
>>>>>>>>>>>>>>>>> 05     HERE: goto HERE;
>>>>>>>>>>>>>>>>> 06   return Halt_Status;
>>>>>>>>>>>>>>>>> 07 }
>>>>>>>>>>>>>>>>> 08
>>>>>>>>>>>>>>>>> 09 int main()
>>>>>>>>>>>>>>>>> 10 {
>>>>>>>>>>>>>>>>> 11   H(D,D);
>>>>>>>>>>>>>>>>> 12   return 0;
>>>>>>>>>>>>>>>>> 13 }
>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>> Can you find any compiler that is liberal enough to 
>>>>>>>>>>>>>>>> accept that?
>>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>>
>>>>>>>>>>>>>>> It has been fully operational code under Windows and
>>>>>>>>>>>>>>> Linux for two years.
>>>>>>>>>>>>>>
>>>>>>>>>>>>>> If your compiler does not reject that program it is not a 
>>>>>>>>>>>>>> conforming
>>>>>>>>>>>>>> C compiler. The semantics according to C standard is that 
>>>>>>>>>>>>>> a diagnostic
>>>>>>>>>>>>>> message must be given. The standard does not specify what 
>>>>>>>>>>>>>> happens if
>>>>>>>>>>>>>> you execute that program anyway.
>>>>>>>>>>>>>>
>>>>>>>>>>>>>
>>>>>>>>>>>>> It is not nit picky syntax that is the issue here.
>>>>>>>>>>>>> The SEMANTICS OF THE C PROGRAMMING LANGUAGE SPECIFIES
>>>>>>>>>>>>>
>>>>>>>>>>>>> No D simulated correctly by any H of every H/D pair specified
>>>>>>>>>>>>> by the above template ever reaches its own line 06 and halts.
>>>>>>>>>>>>
>>>>>>>>>>>> The standard allows that an program is executed but does not
>>>>>>>>>>>> specify what happens when an invalid program is executed.
>>>>>>>>>>>
>>>>>>>>>>> You've cross-posted this to comp.lang.c after a long-running 
>>>>>>>>>>> discussion
>>>>>>>>>>> solely on comp.theory. Presumably you're doing that because 
>>>>>>>>>>> you want
>>>>>>>>>>> some discussion about what the standard says about this code. 
>>>>>>>>>>> For the
>>>>>>>>>>> sake of those of us who have not been following that 
>>>>>>>>>>> discussion on
>>>>>>>>>>> comp.theory, could you please identify what it is that you 
>>>>>>>>>>> think renders
>>>>>>>>>>> this code invalid? Offhand, I don't see anything wrong with 
>>>>>>>>>>> it, but I'm
>>>>>>>>>>> far more reliable when I say "I see an error" than when I say 
>>>>>>>>>>> "I don't
>>>>>>>>>>> see an error".
>>>>>>>>>>>
>>>>>>>>>>>
>>>>>>>>>>>>> Fully operational software that runs under Widows and Linux
>>>>>>>>>>>>> proves that the above is true EMPIRICALLY.
>>>>>>>>>>>>
>>>>>>>>>>>> No, it does not. As the program is not strictly comforming
>>>>>>>>>>>> and uses a non-standard extension some implementation may
>>>>>>>>>>>> execute it differently or refuse to execute.
>>>>>>>>>>>
>>>>>>>>>>> Which non-standard extension does it use?
>>>>>>>>>>
>>>>>>>>>> The main question is whether both arguments of H on the line 
>>>>>>>>>> 00 can have
>>>>>>>>>> the same name.
>>>>>>>>>
>>>>>>>>> That was a typo that I did not believe when told because so may 
>>>>>>>>> people
>>>>>>>>> continue to lie about the behavior of D correctly simulated by H.
>>>>>>>>
>>>>>>>> How does the D that is correctly simulated by H different from any
>>>>>>>> D that is incorrectly simulated by H nor not simulated by H?
>>>>>>>>
>>>>>>>
>>>>>>> typedef int (*ptr)();  // ptr is pointer to int function
>>>>>>> 00 int H(ptr p, ptr i);
>>>>>>> 01 int D(ptr p)
>>>>>>> 02 {
>>>>>>> 03   int Halt_Status = H(p, p);
>>>>>>> 04   if (Halt_Status)
>>>>>>> 05     HERE: goto HERE;
>>>>>>> 06   return Halt_Status;
>>>>>>> 07 }
>>>>>>> 08
>>>>>>> 09 int main()
>>>>>>> 10 {
>>>>>>> 11   H(D,D);
>>>>>>> 12   return 0;
>>>>>>> 13 }
>>>>>>>
>>>>>>> In the above case a simulator is an x86 emulator that correctly
>>>>>>> emulates at least one of the x86 instructions of D in the order
>>>>>>> specified by the x86 instructions of D.
>>>>>>>
>>>>>>> This may include correctly emulating the x86 instructions of H
>>>>>>> in the order specified by the x86 instructions of H thus calling
>>>>>>> H(D,D) in recursive simulation.
>>>>>>>
>>>>>>
>>>>>> Which has been proven incorrect.
>>>>>
>>>>> *Quoted from page 4 of the paper linked below*
>>>>> // Simplified Linz Ĥ (Linz:1990:319)
>>>>> // Strachey(1965) CPL translated to C
>>>>> void P(u32 x)
>>>>> {
>>>>>    if (H(x, x))HERE:
>>>>>     goto HERE;
>>>>> }
>>>>>
>>>>> int main()
>>>>> {
>>>>>    Output("Input_Halts = ", H((u32)P, (u32)P));
>>>>> }
>>>>>
>>>>> That P is correctly simulated by H is proven by the fact that
>>>>> every assembly language instruction of P is correctly simulated
>>>>> by H in the order specified by the x86 assembly language of P
>>>>> even when H correctly simulates itself simulating P.
>>>>>
>>>>> All of the details of this (except the 354 page execution
>>>>> trace of H) are shown on pages 4-5 of the following paper.
>>>>
>>>> Which of course, will have the details of what H did wrong.
>>>>
>>>>>
>>>>> *Halting problem undecidability and infinitely nested simulation*
>>>>> https://www.researchgate.net/publication/351947980_Halting_problem_undecidability_and_infinitely_nested_simulation
>>>>>
>>>>>
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