Sujet : Re: Functions computed by Turing Machines MUST apply finite string transformations to inputs +++
De : rjh (at) *nospam* cpax.org.uk (Richard Heathfield)
Groupes : comp.theoryDate : 04. May 2025, 20:01:17
Autres entêtes
Organisation : Fix this later
Message-ID : <vv8dhv$2kjgk$1@dont-email.me>
References : 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15 16 17 18 19 20 21 22 23 24 25 26 27 28 29
User-Agent : Mozilla Thunderbird
On 04/05/2025 18:30, olcott wrote:
On 5/4/2025 11:21 AM, Richard Heathfield wrote:
On 04/05/2025 17:06, olcott wrote:
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<snip>
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They simply guess that because DD(DD) halts that
DD correctly simulated by HHH must also halt.
>
It's not a guess. If direct execution halts, so must the simulation.
<snip>
Maybe you are confused between halting (reaching
a final halt state and terminating normally)
with stopping running for any reason such as
an aborted emulation. *THEY ARE NOT THE SAME*
Maybe you are confused between equality and inequality.
If DD halts when directly executed, then a correct simulation of DD must also halt. If it fails to do so (no matter for what reason), it is not a correct simulation.
Now, let's take a different angle. You could rationally claim that the simulation doesn't *need* to be correct, provided only that your decider makes the right decision about DD's halting behaviour. You've already established that DD halts when directly executed, so you just need to ensure that your decider reports 'halts' when passed DD as its parameter. How hard could it be?
-- Richard HeathfieldEmail: rjh at cpax dot org dot uk"Usenet is a strange place" - dmr 29 July 1999Sig line 4 vacant - apply within