On 5/2/2022 6:10 PM, Ben wrote:
> olcott <
polc...@gmail.com> writes:
>
>> On 5/2/2022 11:39 AM, Ben wrote:
>>> olcott <
polc...@gmail.com> writes:
>>>
>>>> It is clear that the input to H(P,P) specifies infinitely nested
>>>> simulation to H.
>>> What two pointers must be passed to H for H to tell up about the halting
>>> of P(P)? If H can't report on the halting of the computation P(P) it is
>>> not a halt decider, and you have already told use that H(P,P) == false
>>> and that P(P) halts.
>>
>> If H can report on the halting of non-input P(P) then it is not a
>> decider because deciders only compute the mapping from inputs to final
>> states.
>
> TM deciders compute mappings from inputs to final states /according to
> some property of the inputs/
That par is exactly correct.
> -- whether the input represents, for
That part has been the key error of everyone in that they all believe
that is can represent something other than what it actually specifies.
The correct simulation of the input to H(P,P) specifies non-halting
behavior.
Clueless wonders that don't know the first thing about the x86 language
assume that this simulation is incorrect even though is is nearly
trivial to determine that the simulation is correct as a verified fact.
That they contradict verified facts entirely one the basis that they are
incompetent to verify that it is a fact is the worst hubris.
> example, an even number, a prime number or a halting computation.
>
> According to you there is no "input" (in reality a pair of pointers)
> that represents the halting computation P(P). Why should anyone care
> about this H if it does not decide what we want -- the halting of the
> function call represented by the two arguments to H? Whatever H is
> actually deciding is not interesting.
(a) H does correctly decide its input
(b) H is only required to decide its input.
(c) Therefore H(P,P) is entirely correct on the "impossible" input.
> Also, I wonder why you wasted so much time justifying the fact that
> H(P,P) == false "even though P(P) halts" when H(P,P) is, apparently, not
> even supposed to be deciding the halting P(P). Well, we know, of
> course. You realised you were in a hole so you started to dig sideways.
> You used to know that H(X,Y) had to decide the halting of X(Y). You're
> now pretending it never did!
>
>> That you expect a halt decider to compute the mapping from non-inputs
>> is a little nuts when you know that deciders can't possibly do this.
>
> Don't be silly. They decide properties of inputs -- parity, halting and
> so on. You'd know this if you'd done even the warm-up exercises I set.
The problem here is that you expect that the property of an input not be
the actual property of the actual input but the property of a non-input.
The halting property of the input to H(P,P) is the actual behavior of
the correct simulation of this input and thus not at all what you simply
imagine this property should be.
> How are they coming along? It looks like you have found an excuse to
> bail out again:
>
It is coming along great and it is wonderful fun.
I think that it is a great idea to move in this direction.
I may eventually convert C copy of the TM into a RASP machine.
I probably won't begin to do that until after we finish our exercises.
>> It turns out that I can create a whole TM interpreter from scratch
>> quicker than I can learn the extraneous complexity of the TM
>> Interpreter
http://www.lns.mit.edu/~dsw/turing/turing.html
>
> I doubt it. But I suppose you think that's a reasonable excuse. Of
> course, some of us remember you saying writing such a thing would take
> about a week three years ago. I remember wondering how such a simple
> program could take you a week to write.
As soon as I complete the detailed design I should have an accurate
estimate of the total time. It currently looks like < 4 hours. I have
spent 15 minutes on the detailed design and it looks like it will take
45 more minutes.
One thing that is great is that I have fully recovered from what could
have been a life threatening infection. I was in the hospital getting IV
antibiotics for nearly two days. Chemotherapy patients have a few days
after chemotherapy where their immune system is very close to zero.
>
> Of course you don't need an interpreter to write E or specify P, but you
> must find some excuse for bailing out.
>
It is much better (and more fun) if I make this totally concrete.
One can not effectively debug code by desk checking.