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From: Mikko <mikko.levanto@iki.fi>
Newsgroups: comp.theory
Subject: Re: Hypothetical possibilities
Date: Fri, 26 Jul 2024 11:05:07 +0300
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On 2024-07-24 13:38:08 +0000, olcott said:

> On 7/24/2024 4:01 AM, Mikko wrote:
>> On 2024-07-23 14:41:11 +0000, olcott said:
>> 
>>> On 7/23/2024 2:32 AM, Mikko wrote:
>>>> On 2024-07-22 15:05:41 +0000, olcott said:
>>>> 
>>>>> On 7/22/2024 6:05 AM, Mikko wrote:
>>>>>> On 2024-07-20 15:28:31 +0000, olcott said:
>>>>>> 
>>>>>>> void DDD()
>>>>>>> {
>>>>>>>    HHH(DDD);
>>>>>>> }
>>>>>>> 
>>>>>>> int main()
>>>>>>> {
>>>>>>>    DDD();
>>>>>>> }
>>>>>>> 
>>>>>>> (a) Termination Analyzers / Partial Halt Deciders must halt
>>>>>>> this is a design requirement.
>>>>>> 
>>>>>> For a partial analyzer or deciders this is not always required.
>>>>>> 
>>>>> 
>>>>> *You can't even get my words correctly*
>>>>> A termination analyzer must report on the behavior of at least
>>>>> one input for all of the inputs of this one input. This is
>>>>> met when a termination analyzer analyzes an input having no inputs.
>>>>> 
>>>>> A partial halt decider must correctly determine the halt status
>>>>> of at least one input and its specific input (if any).
>>>>> 
>>>>> HHH is both a partial halt decider and a termination analyzer
>>>>> for DDD and a few other inputs having no input.
>>>>> 
>>>>>>> (b) Every simulating termination analyzer HHH either
>>>>>>> aborts the simulation of its input or not.
>>>>>> 
>>>>>> This must be interpreted to mean that a simulating termination analyzer
>>>>>> may abort its simulation for some simulated abort and simulate others
>>>>>> to the termination.
>>>>>> 
>>>>> 
>>>>> I am talking about hypothetical possible ways that HHH could be encoded.
>>>>> (a) HHH(DDD) is encoded to abort its simulation.
>>>>> (b) HHH(DDD) is encoded to never abort its simulation.
>>>>> 
>>>>>>> (c) Within the hypothetical case where HHH does not abort
>>>>>>> the simulation of its input {HHH, emulated DDD and executed DDD}
>>>>>>> never stop running.
>>>>>> 
>>>>>> The case is not very hypothetical. Given the HHH you already have,
>>>>>> it is fairly easy to construct the "hypothetical" HHH and see what
>>>>>> it actually does.
>>>>>> 
>>>>> 
>>>>> (a) HHH(DDD) is encoded to abort its simulation.
>>>>> (b) HHH(DDD) is encoded to never abort its simulation.
>>>>> 
>>>>>>> This violates the design requirement of (a) therefore HHH must
>>>>>>> abort the simulation of its input.
>>>>>> 
>>>>>> The violation simply means that the "hypothetical" HHH is not a
>>>>>> termination analyzer of partial halt decider in sense (a). What
>>>>>> it "must" be or do depends on the requirements.
>>>>>> 
>>>>> Therefore (a) is correct and (b) is incorrect according to the
>>>>> design requirements for HHH that it must halt.
>>>>> 
>>>>> It is also a truism that any input that must be aborted
>>>>> is a non-halting input.
>>>> 
>>>> No, it is not. The "must" and "non-halting" belong to different worlds.
>>>> The word "must" blongs to requirements. The word "non-halting" is a
>>>> feature of a program. They are unrelated, so one cannot be inferred
>>>> from the other.
>>>> 
>>> 
>>> When-so-ever there are two hypothetical possible way to encode
>>> a simulating halt decider for a specific input
>>> (a) one aborts its simulation of DDD
>>> (b) never aborts its simulation of DDD
>> 
>> Does the simulator that simulates the beginning and end of the
>> simulated computation but skips a part in ghe middle belong to
>> class (a) or class (b)?
>> 
> 
> That is off topic. I am only referring to  a sequence of
> 1 to N x86 machine language instructions simulated according
> to the x86 semantic meaning of these instructions.

No, it isn't. Abortion of simulation is a deviation form x86 macine
language semantics. What I ask about does not deviate more.

-- 
Mikko