Cellular Automata

IdleRich

IdleRich
Yeah I think we are probably talking about different things. I'm talking about the cellular automata (of which the Life game is an example) which are generated by deterministic algorithms and are therefore deterministic and will, by definition, give the same output if you run one several times with the same starting parameters and inputs. If you look at the videos you will see they use it to build a computer, which of course relies on this - you can't have a computer that tells you today that 2 plus 2 is 4, but tomorrow tells you it's 17.

You could of course have things generated by an algorithm with probabilistic/random elements and this would not always give the same results for same inputs. But this is quite different from the stuff discussed at the start of the thread.
 

Mr. Tea

Let's Talk About Ceps
He said "it's non-deterministic" and you said "yeah" - but then I said "I think that's wrong, it is deterministic" and you said "yeah that's right".

I think it's just a mix-up with terminology. The thing is, the ones on the first pages that I read about have a rule that generates them, the rule is of the form, if it's like this do x, if it's like that do y etc.

These rules are deterministic, they contain no random or probabilistic element - although you can normally choose your starting conditions and inputs and various other parameters - and what makes them interesting is that these very simple, deterministic rules generate very complex things. But if you did the same program twice, with the same input parameters etc you would get the same result.

But the, I think, counter-intuitive thing, is that very simple, deterministic rules generate very complicated patterns. And in fact in many cases even though we know and understand the rule, and we choose the starting conditions, we often can't work out where it will end up, or what type of pattern it will end up being - other than by actually just doing it.

So I think it's tempting to think that cos we know the inputs and we know the generating rule, but we don't know where it will end up, that the explanation for us seemingly sort of getting lost between the known start, and the unpredictable result is that it's non-deterministic, but that's not it - we lose the ability to predict where it will go not cos of randomness or non-determinism, but simply because of complexity* or undecidability.

Just cos we it's impossible to predict we want to say it's random, but it's not, it's something that our mind wants to interpret that way, cos we are not used to something where we know the start and we know precisely every step, and yet we can't tell where it will end up. That's right ain't it @Slothrop, @MrTea?

*Great/terrible mangling of the language "simply because of complexity"
Not my particular area of expertise, but yeah, saying a system is deterministic in the strict sense (identical starting conditions lead to identical outcomes) is consistent with it being 'random' in practice, since the very simple laws governing its behaviour give rise to evolutionary processes that are too complex for us to understand or predict.
 

Clinamenic

Binary & Tweed
I mean, the only way we can have non-deterministic computing is with quantum, right? Even with noise or randomness, the input-to-output relationship is still constant and deterministic, save for some kind of hardware malfunction edgecases maybe (vaguely recall something about magnetic interference with hard drives, but I could totally be misunderstanding that).
 

IdleRich

IdleRich
Not my particular area of expertise, but yeah, saying a system is deterministic in the strict sense (identical starting conditions lead to identical outcomes) is consistent with it being 'random' in practice, since the very simple laws governing its behaviour give rise to evolutionary processes that are too complex for us to understand or predict.
It's beyond our power to predict, but it's not random. Random does not mean the same thing as not-predictable.
 

IdleRich

IdleRich
I mean, the only way we can have non-deterministic computing is with quantum, right? Even with noise or randomness, the input-to-output relationship is still constant and deterministic, save for some kind of hardware malfunction edgecases maybe (vaguely recall something about magnetic interference with hard drives, but I could totally be misunderstanding that).
But couldn't you have a computer program that at some stage printed the command "Operator, roll a dice and enter the number you get" and different numbers take you on a different path?

That would be a non-deterministic ie random computer program cos it has at least one stage that is not just too complex to predict but is random. If you ran it several times with the same starting conditions and inputs you could easily still get a different result, cos at the dice rolling stage it might take a path.

So something that does that is fundamentally different from the Life Game say. I dunno if that's cheating or if quantum computers do something like that without involving a person, but it doesn't seem that complicated to make it non-deterministic.
 

Mr. Tea

Let's Talk About Ceps
I mean, the only way we can have non-deterministic computing is with quantum, right? Even with noise or randomness, the input-to-output relationship is still constant and deterministic, save for some kind of hardware malfunction edgecases maybe (vaguely recall something about magnetic interference with hard drives, but I could totally be misunderstanding that).
I think quantum computing can't be "non-deterministic", as such, for the simple reason that you'd hope any computer, of any sort, would give the same answer twice if made to perform the same computation twice. So I don't know if quantum computing, as it currently exists, can do things that are inherently impossible for conventional computers, as opposed to just vastly faster.

Now Roger Penrose has worked out a scheme whereby QM, in conjunction with gravity, supposedly enables neurons to perform calculations that are formally undecidable under the axioms of logic. The trouble is that it relies on relatively 'large' objects, by quantum standards - namely microtubules, very large organic molecules - remaining in a state of quantum coherence for an implausibly long time, whereas the brain, being a dense, warm, messy sort of thing, is exactly the wrong kind of environment for this phenomenon to occur.
 

Mr. Tea

Let's Talk About Ceps
Here's an excellent video of emergent complexity, viz. a complex system spontaneously arising from basic automata operating according to simple rules.

Actually this brings up an important philosophical point, namely: Quis spotiet ipsos spotodes?
 
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