Re: Simulating termination analyzers by dummies --- What does halting mean?

Am Wed, 19 Jun 2024 10:07:21 -0500 schrieb olcott:

On 6/19/2024 9:11 AM, Fred. Zwarts wrote:

Op 19.jun.2024 om 15:11 schreef olcott:

On 6/19/2024 3:18 AM, Fred. Zwarts wrote:

Op 18.jun.2024 om 19:25 schreef olcott:

On 6/18/2024 12:06 PM, joes wrote:

It is correct do say that the simulated input did not terminate
normally, thus defining the notion of abnormal termination within
Turing machines.

The simulated input did not terminate at all, the simulator did. If it
hadn't aborted (which the input gave no reason to, or even has the power),
the simulation would have continued.

Similarly, when your H, H0, or other H simulates itself, its
simulation aborts one cycle too early and therefore the non-halting
conclusion is incorrect.

I was confused bout this for three days four years ago and then I got
over it. No simulating termination analyzer can wait for an inner
instance of itself to abort the simulation or it waits forever.

Exactly. It can never correctly abort.

No, I understand it perfectly, but it seems to be over your head. We
agree that H needs to stop to prevent infinite recursion, but it is
over your head to see that when it stops, it misses the part of itself
where its simulation also stops, one repeating state further. So, the
non-halting conclusion is wrong, because the abort is premature.

Every C programmer has agreed thus you simply don't know these things
well enough.

Ad hominem is not an argument.
It may abort if the input didn't halt; but it does, because it is the same
as itself.

So, your reasoning must lead to the only possible conclusion that a
simulator is unable to simulate itself properly, which causes false
negatives if its return value must be interpreted as a non-halting
behaviour. Instead, a return value of 'false' indicates an 'unable to
simulate' state of the simulator, which is not equivalent to
'non-halting'.

--
joes