Path: news.eternal-september.org!eternal-september.org!.POSTED!not-for-mail
From: Mikko <mikko.levanto@iki.fi>
Newsgroups: comp.theory
Subject: Re: Halting Problem: What Constitutes Pathological Input
Date: Thu, 8 May 2025 12:54:55 +0300
Organization: -
Lines: 56
Message-ID: <vvhv1f$1mas0$1@dont-email.me>
References: <GE4SP.47558$VBab.42930@fx08.ams4> <vvamqc$o6v5$4@dont-email.me> <vvan7q$o4v0$1@dont-email.me> <ts5SP.113145$_Npd.41800@fx01.ams4> <vvat0g$vtiu$1@dont-email.me> <vvcl54$2lap7$1@dont-email.me> <vvd9tn$37t3c$1@dont-email.me> <d9781891e41d9a52c7a54d99ebdaea47c6e2e5a2@i2pn2.org> <vvdl2g$3i09b$1@dont-email.me> <vvfa9r$um4q$1@dont-email.me> <vvfohr$11mbc$2@dont-email.me>
MIME-Version: 1.0
Content-Type: text/plain; charset=utf-8; format=flowed
Content-Transfer-Encoding: 8bit
Injection-Date: Thu, 08 May 2025 11:54:56 +0200 (CEST)
Injection-Info: dont-email.me; posting-host="43f04a5acf00667023a752795a945cf1";
	logging-data="1780608"; mail-complaints-to="abuse@eternal-september.org";	posting-account="U2FsdGVkX19kyaUdqa4/eBJCCovBq7zP"
User-Agent: Unison/2.2
Cancel-Lock: sha1:KCNsasEj0Pjl0gzFT0daMAuZCNY=

On 2025-05-07 13:51:55 +0000, olcott said:

> On 5/7/2025 4:48 AM, Mikko wrote:
>> On 2025-05-06 18:40:16 +0000, olcott said:
>> 
>>> On 5/6/2025 10:53 AM, joes wrote:
>>>> Am Tue, 06 May 2025 10:29:59 -0500 schrieb olcott:
>>>>> On 5/6/2025 4:35 AM, Mikko wrote:
>>>>>> On 2025-05-05 17:37:20 +0000, olcott said:
>>>> 
>>>>>>> The above example is category error because it asks HHH(DD) to report
>>>>>>> on the direct execution of DD() and the input to HHH specifies a
>>>>>>> different sequence of steps.
>>>>>> 
>>>>>> No, it does not. The input is DD specifides exactly the same sequence
>>>>>> of steps as DD. HHH just answers about a different sequence of steps
>>>>>> instead of the the seqeunce specified by its input.
>>>> As agreed to below:
>>>> 
>>>>> <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
>>>>> 
>>>>> *input D* is the actual input *would never stop running unless aborted*
>>>>> is the hypothetical H/D pair where H does not abort.
>>> 
>>>> H should simulate its actual input D that calls the aborting H, not a
>>>> hypothetical version of D that calls a pure simulator.
>>>> 
>>> 
>>> *would never stop running unless aborted*
>>> refers to the same HHH that DD calls yet
>>> this hypothetical HHH does not abort.
>>> 
>>>>> You cannot possibly show the exact execution trace where DD is correctly
>>>>> emulated by HHH and this emulated DD reaches past its own machine
>>>>> address [0000213c].
>>> 
>>>> Duh, no simulator can simulate itself correctly. But HHH1 can simulate
>>>> DD/HHH.
>>>> 
>>> 
>>> HHH does simulate itself correctly yet must create
>> 
>> No, it cannot simulate itself to the point where it returns.
> 
> HHH(DD) does return.

Yes, but HHH cannot simulate that.

When HHH(DD) returns it returns the wrong value.

-- 
Mikko