Path: ...!eternal-september.org!feeder3.eternal-september.org!news.eternal-september.org!eternal-september.org!.POSTED!not-for-mail
From: "Fred. Zwarts" <F.Zwarts@HetNet.nl>
Newsgroups: comp.theory
Subject: Re: DD emulated by HHH cannot possibly terminate normally --- x86
 code
Date: Sat, 1 Mar 2025 23:05:29 +0100
Organization: A noiseless patient Spider
Lines: 57
Message-ID: <vq00bb$cc27$1@dont-email.me>
References: <vptlfu$3st19$9@dont-email.me>
 <d128909f1359b48293dd1823d22d671435d5640c@i2pn2.org>
 <vpv6ad$8sdm$1@dont-email.me> <vpv9o6$8k7n$1@dont-email.me>
 <vpvcta$a44l$1@dont-email.me> <vpvpvd$cc26$1@dont-email.me>
 <vpvt55$bjn9$14@dont-email.me>
MIME-Version: 1.0
Content-Type: text/plain; charset=UTF-8; format=flowed
Content-Transfer-Encoding: 8bit
Injection-Date: Sat, 01 Mar 2025 23:05:31 +0100 (CET)
Injection-Info: dont-email.me; posting-host="78ea2e407625ee7c3e478257aed62108";
	logging-data="405575"; mail-complaints-to="abuse@eternal-september.org";	posting-account="U2FsdGVkX18x161QfKZSD6bis0hJQzzh"
User-Agent: Mozilla Thunderbird
Cancel-Lock: sha1:30iz1YPHUb4Y8p6J9hHjQl+RyIk=
In-Reply-To: <vpvt55$bjn9$14@dont-email.me>
Content-Language: nl, en-GB
Bytes: 3934

Op 01.mrt.2025 om 22:11 schreef olcott:
> On 3/1/2025 2:16 PM, Fred. Zwarts wrote:
>> Op 01.mrt.2025 om 17:33 schreef olcott:
>>> On 3/1/2025 9:39 AM, Fred. Zwarts wrote:
>>>> Op 01.mrt.2025 om 15:41 schreef olcott:
>>>>> On 3/1/2025 6:49 AM, Richard Damon wrote:
>>>>>> On 2/28/25 7:47 PM, olcott wrote:
>>>>>>> _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 we hypothesize that the code at machine address
>>>>>>> 0000213c is an x86 emulator then we know that DD
>>>>>>> remains stuck in recursive emulation and cannot possibly
>>>>>>> reach its own "ret" instruction and terminate normally.
>>>>>>>
>>>>>>> When we add the additional complexity that HHH also
>>>>>>> aborts this sequence at some point then every level
>>>>>>> of recursive emulation immediately stops. This does
>>>>>>> not enable any DD to ever reach its "ret" instruction.
>>>>>>>
>>>>>>
>>>>>> But then you just negated your first assumption, as a partial 
>>>>>> emulator that aborts its emulation, then DD no longer gets stuck.
>>>>>>
>>>>>
>>>>> Cannot possibly reach its own "ret" instruction and terminate normally
>>>> proves failure of HHH to reach the end of a proven terminating program.
>>>
>>> DD emulated by HHH according to the above x86 machine code of DD
>>> cannot possibly reach its own "ret" instruction and terminate normally
>>
>>
>> In other words, 
> 
> The DD input to HHH unequivocally specifies a
> non terminating computation.
In other words, HHH did not terminate the simulation.
Is that great news? It is easy to write a simulator that does not 
terminate its simulation, e.g. by aborting after one instruction. So 
Olcott's criterium is that all programs will specify a non-terminating 
computation to such a simulator. It cannot possibly reach the 'ret' 
instruction.
Can we agree that that is a failure of the simulator, not of the program?