Path: news.eternal-september.org!eternal-september.org!.POSTED!not-for-mail
From: dbush <dbush.mobile@gmail.com>
Newsgroups: comp.lang.c
Subject: Re: DD simulated by HHH cannot possibly halt (Halting Problem)
Date: Sat, 5 Apr 2025 12:25:12 -0400
Organization: A noiseless patient Spider
Lines: 128
Message-ID: <vsrlh7$2n0kg$1@dont-email.me>
References: <vsnchj$23nrb$2@dont-email.me> <vsngo6$26agq$1@dont-email.me>
 <vsnh44$26c94$3@dont-email.me> <vsnht7$26agq$2@dont-email.me>
 <vsnlvv$2h8pt$1@dont-email.me> <vsnnb5$2g4cd$2@dont-email.me>
 <vsnnug$2h8pt$2@dont-email.me> <vsnou2$2g4cd$5@dont-email.me>
 <vspqmt$o89d$1@dont-email.me> <vsq97g$19eo9$1@dont-email.me>
 <vsqhov$1hl94$1@dont-email.me> <vsqmth$1mglg$2@dont-email.me>
 <vsrk17$2le7u$1@dont-email.me>
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding: 8bit
Injection-Date: Sat, 05 Apr 2025 18:25:12 +0200 (CEST)
Injection-Info: dont-email.me; posting-host="43eaa133a904c8986c7a0672d25633a8";
	logging-data="2851472"; mail-complaints-to="abuse@eternal-september.org";	posting-account="U2FsdGVkX1+w58IR8dNBRefnNgmzNF/K"
User-Agent: Mozilla Thunderbird
Cancel-Lock: sha1:l+6RJT6xaAWb2b67f6TDXMQK9xY=
Content-Language: en-US
In-Reply-To: <vsrk17$2le7u$1@dont-email.me>

On 4/5/2025 11:59 AM, olcott wrote:
> On 4/5/2025 2:42 AM, Richard Heathfield wrote:
>> On 05/04/2025 07:14, olcott wrote:
>>> On 4/4/2025 10:49 PM, Richard Heathfield wrote:
>>>> On 05/04/2025 00:41, olcott wrote:
>>>>> *Simulating termination analyzer Principle*
>>>>> It is always correct for any simulating termination
>>>>> analyzer to stop simulating and reject any input that
>>>>> would otherwise prevent its own termination. The
>>>>> only rebuttal to this is rejecting the notion that
>>>>> deciders must always halt.
>>>>
>>>
>>> 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);
>>> }
>>>
>>>> In other words, you operate on the principle that deciders don't 
>>>> have to (and indeed can't) always make a correct decision on whether 
>>>> an input program halts.
>>>>
>>>
>>> The termination analyzer HHH would be correct
>>> to determine that it must stop simulating DD to
>>> prevent its own non-termination
>>
>> Fine, but then it fails to do its job. What you are learning (albeit 
>> slowly) is that the termination analyser HHH can't analyse whether DD 
>> terminates. It is therefore not a general purpose termination analyser.
>>
> 
> Introduction to the Theory of Computation 3rd Edition
> by Michael Sipser (Author) (best selling textbook)
> 
> <MIT Professor Sipser agreed to ONLY these verbatim words 10/13/2022>
>      If simulating halt decider H correctly simulates its input D
>      until H correctly determines that its simulated D would never
>      stop running unless aborted then
> 
>      H can abort its simulation of D and correctly report that D
>      specifies a non-halting sequence of configurations.
> </MIT Professor Sipser agreed to ONLY these verbatim words 10/13/2022>

But not what you think he agreed to:


On Monday, March 6, 2023 at 2:41:27 PM UTC-5, Ben Bacarisse wrote:
 > Fritz Feldhase <franz.fri...@gmail.com> writes:
 >
 > > On Monday, March 6, 2023 at 3:56:52 AM UTC+1, olcott wrote:
 > >> On 3/5/2023 8:33 PM, Fritz Feldhase wrote:
 > >> > On Monday, March 6, 2023 at 3:30:38 AM UTC+1, olcott wrote:
 > >> > >
 > >> > > I needed Sipser for people [bla]
 > >> > >
 > >> > Does Sipser support your view/claim that you have refuted the 
halting theorem?
 > >> >
 > >> > Does he write/teach that the halting theorem is invalid?
 > >> >
 > >> > Tell us, oh genius!
 > >> >
 > >> Professor Sipser only agreed that [...]
 > >
 > > So the answer is no. Noted.
 > >
 > >> Because he has >250 students he did not have time to examine anything
 > >> else. [...]
 > >
 > > Oh, a CS professor does not have the time to check a refutation of the
 > > halting theorem. *lol*
 > I exchanged emails with him about this. He does not agree with anything
 > substantive that PO has written. I won't quote him, as I don't have
 > permission, but he was, let's say... forthright, in his reply to me.
 >

On 8/23/2024 5:07 PM, Ben Bacarisse wrote:
 > joes <noreply@example.org> writes:
 >
 >> Am Wed, 21 Aug 2024 20:55:52 -0500 schrieb olcott:
 >
 >>> Professor Sipser clearly agreed that an H that does a finite simulation
 >>> of D is to predict the behavior of an unlimited simulation of D.
 >>
 >> If the simulator *itself* would not abort. The H called by D is,
 >> by construction, the same and *does* abort.
 >
 > We don't really know what context Sipser was given.  I got in touch at
 > the time so do I know he had enough context to know that PO's ideas were
 > "wacky" and that had agreed to what he considered a "minor remark".
 >
 > Since PO considers his words finely crafted and key to his so-called
 > work I think it's clear that Sipser did not take the "minor remark" he
 > agreed to to mean what PO takes it to mean!  My own take if that he
 > (Sipser) read it as a general remark about how to determine some cases,
 > i.e. that D names an input that H can partially simulate to determine
 > it's halting or otherwise.  We all know or could construct some such
 > cases.
 >
 > I suspect he was tricked because PO used H and D as the names without
 > making it clear that D was constructed from H in the usual way (Sipser
 > uses H and D in at least one of his proofs).  Of course, he is clued in
 > enough know that, if D is indeed constructed from H like that, the
 > "minor remark" becomes true by being a hypothetical: if the moon is made
 > of cheese, the Martians can look forward to a fine fondue.  But,
 > personally, I think the professor is more straight talking than that,
 > and he simply took as a method that can work for some inputs.  That's
 > the only way is could be seen as a "minor remark" with being accused of
 > being disingenuous.

On 8/23/2024 9:10 PM, Mike Terry wrote:
 > So that PO will have no cause to quote me as supporting his case:  what
 > Sipser understood he was agreeing to was NOT what PO interprets it as
 > meaning.  Sipser would not agree that the conclusion applies in PO's
 > HHH(DDD) scenario, where DDD halts.