jimrandomh comments on Frequentist Magic vs. Bayesian Magic - Less Wrong

41 Post author: Wei_Dai 08 April 2010 08:34PM

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Comment author: RolfAndreassen 09 April 2010 11:31:47PM 1 point [-]

I don't understand why your universal prior passes the tape through the Turing machine. If you have a source of genuinely random tape inputs in the first place, why not just use the probability that a tape has the first four bits '1100'? And in any case, what's the advantage of invoking Turing machinery in place of the good old fair coins?

Comment author: jimrandomh 10 April 2010 12:02:09AM 3 points [-]

The trick, and the reason for using Turing machines, is that '0000' and '1111' ought to be considered more likely than '0101' and '1010', because they're simpler; and the way this model represent simplicity, a sequence is simple if it's the output of short programs (where 'program' in this case means 'prefix to a Turing machine tape'). If you used the tape directly, then '0000000000' and '0100011011' would be equally likely, which, generally speaking, they're not.