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From: Richard Damon <richard@damon-family.org>
Newsgroups: comp.theory
Subject: Re: Who here understands that the last paragraph is Necessarily true?
 --- Self-Modifying Turing Machine
Date: Sun, 21 Jul 2024 15:27:13 -0400
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On 7/21/24 2:33 PM, joes wrote:
> Am Sun, 21 Jul 2024 08:58:56 -0500 schrieb olcott:
>> On 7/21/2024 4:52 AM, Mikko wrote:
>>> On 2024-07-20 13:03:50 +0000, olcott said:
>>>> On 7/20/2024 4:01 AM, Mikko wrote:
>>>>> On 2024-07-19 14:18:05 +0000, olcott said:
> 
>>>> A self modifying TM is merely a TM description that is simulated by a
>>>> UTM and has access to itself on the UTM tape.
> Please explain how the two machines don't overwrite each other.
> Or how the simulated one manages to break out and change the "UTM".

I think the self-modifying-Turing-Machine doesn't change the "UTM" (that 
can't actually be a UTM) but changes its "description" on the tape that 
lives with its input tape.

Of course, PO describes it with wrong words that makes it fundamentally 
incorrect.

I suspect that the biggest issue trying to implement something like that 
is figuring an encoding for the "description" that allows for the slow 
manipulation of it that would be inherent in being updated by a Turing 
Machine like program, while still keeping it parseable enough for the 
engine to keep running it.

There would surely need to be extensive "rules" about what intermediate 
encodings are allowed to exist or not exist on the tape in that region.

Also, unlike how it seem Olcott view it, the emulated machine would not 
be "directly" accessing the actual tape of the master machine, but would 
be seeing an emulated virtual tape.
> 
>>> If it is executed as self-modifying that exectuion is not simulation,
>>> as a simulation does not do what the simulated does not do. A simulator
>>> that simulates a self-modifying automaton is not an UTM.
>> When a simulated Turing Machine Description is provided access to itself
>> on the UTM tape it can do the same thing.
> The description on the tape is not running. It can't have access to its
> own hardware.
>