smoofra comments on No Universal Probability Space - Less Wrong

0 Post author: gworley 06 May 2009 02:58AM

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Comment author: smoofra 07 May 2009 01:12:02PM 4 points [-]

One way of making such a space is to take all recursive functions of some universal computer, run them, and storing the output,

OK....

resulting in an universal probability space because every possible set of events will be there

what!? You haven't yet described a probability space. The aforementioned set is infinite, so the uniform distribution is unavailable. What probability distribution will you have on this set of recursive-function-runs. And in what way is the resulting probability space universal?

Comment author: kim0 comment score below threshold [+] (7 children)

Comment author: smoofra 07 May 2009 04:12:14PM * 0 points [-]

All that will be answered if you study "algorithmic information theory", or "Kolmogorov komplexity"

I have. I'm not an expert in it, but I'm quite aware of the concept.

You have not specified a probability space, and you have not made any attempt to justify calling the space you didn't specify "universal"

Thats the book I read, some years after I invented it myself.

uh huh.

Comment author: kim0 08 May 2009 09:51:52AM -1 points [-]

You are wrong because I did specify a probability space.

The probability space I specified was one where the sample space was the set of all outputs of all programs for some universal computer, and the measure was one from the book I mentioned. One could for instance choose the Solomonoff measure, from 4.4.3.

From your writings I conclude that is it quite likely that you are neither quite aware of the concept, nor understanding what I write, while believing you do.

Comment author: smoofra 08 May 2009 04:49:37PM 0 points [-]

You are wrong because I did specify a probability space.

No, you specified the points and not the measure.

The probability space I specified was one where the sample space was the set of all outputs of all programs for some universal computer, and the measure was one from the book I mentioned. One could for instance choose the Solomonoff measure, from 4.4.3.

OK! Now we've got a space. Of course if you wanted to talk about solomonoff measure, why didn't you just say so 5 comments ago. Pretty much everyone reading less wrong would have immediately known what you were talking about. You still haven't justified calling the solomonoff space "universal".

From your writings I conclude that is it quite likely that you are neither quite aware of the concept, nor understanding what I write, while believing you do.

Now you're just being rude. You don't know me, you certainly don't know what I do or don't know.

Comment author: kim0 08 May 2009 08:03:34PM -2 points [-]

It is universal, because every possible sequence is generated.

It is universal, because it is based on universally recursive functions.

It is universal, because it uses an universal computer.

People knowing algorithmic complexity know that it is about probability measures, spaces, universality, etc. You apparently did not, while nitpicking instead.

Comment author: smoofra 08 May 2009 09:01:56PM * 0 points [-]

I'm not nitpicking, you're wrong. "Universal" in this context means, to quote the original poster

i.e. the probability space of all events that could occur at some time during the existence of the universe

What the heck does that have to do with every possible sequence being generated? For that matter what does it have to do with sequences at all? The solomonoff measure is a measure over sequences in a finite alphabet, or to put it simpler, Integers. How do I express an event like "it will rain next tuesday" as a subset of the integers?

Whatever you are using the word "universal" to mean, it is not anything like what the OP had in mind. The Solomonoff measure is an interesting mathematical object for sure, and it may be quite relevant to the topic of real-world Bayesian reasoning, but it's obviously not universal in that sense.

also: what the heck does "universally recursive" mean? Did you just make up that term right now? Because I've never heard it before, it only has 10 google hits, and none of them are relevant to this discussion.

Comment author: kim0 comment score below threshold [+] (1 child)

smoofra comments on No Universal Probability Space - Less Wrong

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