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Viliam_Bur comments on Open Thread, May 19 - 25, 2014 - Less Wrong Discussion

2 Post author: somnicule 19 May 2014 04:49AM

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Comment author: Viliam_Bur 19 May 2014 06:27:33PM *  1 point [-]

the maximally unexpected sequence will be random

In a random sequence, AIXI would guess on average half of the bits. My goal was to create a specific sequence, where it couldn't guess any. Not just a random sequence, but specifically... uhm... "anti-inductive"? The exact opposite of lawful, where random is merely halfway opposed. I don't care about other possible predictors, only about AIXI.

Imagine playing rock-paper-scissors against someone who beats you all the time, whatever you do. That's worse than random. This sequence would bring the mighty AIXI to tears... but I suspect to a human observer it would merely seem pseudo-random. And is probably not very useful for other goals than making fun of AIXI.

Comment author: Nisan 20 May 2014 01:53:57AM *  3 points [-]

Ok. I still think the sequence is random in the algorithmic information theory sense; i.e., it's incompressible. But I understand you're interested in the adversarial aspect of the scenario.

You only need a halting oracle to compute your adversarial sequence (because that's what it takes to run AIXI). A super-Solomonoff inductor that inducts over all Turing machines with access to halting oracles would be able to learn the sequence, I think. The adversarial sequence for that inductor would require a higher oracle to compute, and so on up the ordinal hierarchy.

Comment author: ShardPhoenix 20 May 2014 12:12:40AM 0 points [-]

Shouldn't AIXI include itself (for all inputs) recursively? If so I don't think your sequence is well defined.

Comment author: Nisan 20 May 2014 01:54:55AM 4 points [-]

No, AIXI isn't computable and so does not include itself as a hypothesis.

Comment author: ShardPhoenix 20 May 2014 04:36:13AM 0 points [-]

Oh, I see.