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On 2025-05-15 00:36:21 +0000, Mike Terry said:Mike explains all of the details of exactly how a
On 14/05/2025 22:31, Keith Thompson wrote:The details of H are not known to Sipser, so he can't know whether aolcott <polcott333@gmail.com> writes:>On 5/14/2025 3:51 PM, dbush wrote:>On 5/14/2025 11:45 AM, olcott wrote:>On 5/14/2025 6:20 AM, Richard Damon wrote:That Sipser didn't agree what you think the above means:>>
And since the DD that HHH is simulating WILL HALT when fully
simulated (an action that HHH doesn't do)
*NOT IN THE ACTUAL SPEC*
<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
>
>
If that was actually true then you could provide an
alternative meaning for the exact words stated above.
>
I keep challenging you to provide this alternative
meaning and you dodge because you know that you are
lying about there being any alternative meaning
FOR THE EXACT WORDS LISTED ABOVE.
No alternative meaning is needed, just a correct interpretation of the
words (which appear to be incomplete).
>
The quoted sentence is cut off, something that I suspect you didn't
notice. Here's the full quotation from a previous article:
>><Sipser approved abstract>
MIT Professor Michael Sipser has agreed that the following verbatim
paragraph is correct (he has not agreed to anything else in this
paper):
>
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 H can abort its simulation of D and correctly
report that D specifies a non-halting sequence of configurations.
</Sipser approved abstract>
**If** H correctly simulates its input in the manner you claim,
**then** H can correctly report the halting status of D. (That's a
paraphrase that probably doesn't capture the full meaning; the full
**quotation is above.)
>
To put it another way, If H correctly simulated its input in
the manner you claim, then H could correctly report the halting
status of D.
>
I'm not surprised that Sipser would agree to that. The problem is
that it's a conditional statement whose premise is impossible.
>
If an equilateral triangle had four sides, then each of its four
vertices would be 90 degrees. That doesn't actually mean that
there exists an equilateral triangle with four 90-degree vertices,
and in fact no such triangle exists. Similarly, *if* a general
halt decider existed, then there are a lot of things we could say
about it -- but no general halt decider can exist.
>
I'm not quite 100% confident in my reasoning here. I invite any
actual experts in computational theory (not you, PO) to criticize
what I've written.
I doubt that Sipser would be using your interpretation, relying on a false premise as a clever kind of logical loop-hole to basically fob someone off.
premise is false. It is possible that some simulating partial decider
correctly simulates a part of the behaviour of some D and correctly
determines that the unsimulated part of the behaviour never halts;
for example, if the unsimulated part is a trivial eternal loop. That
one premise is false about HHH with DDD is a part of what was asked.
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