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Stuart_Armstrong comments on Versions of AIXI can be arbitrarily stupid - Less Wrong Discussion
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We have the universal explorer - it will figure out everything, if it survives, but it'll almost certainly kill itself.
We have the bad AIXI model above - it will survive for a long time, but is trapped in a bad epistemic state.
What would be ideal would be a way of establishing the minimal required exploration rate.
Do you mean a way of establishing this independent of the prior, i.e., the agent will explore at some minimum rate regardless of what prior we give it? I don't think that can be right, since the correct amount of exploration must depend on the prior. (By giving AIXI a different bad prior, we can make it explore too much instead of too little.) For example suppose there are physics theories P1 and P2 that are compatible with all observations so far, and an experiment is proposed to distinguish between them, but the experiment will destroy the universe if P1 is true. Whether or not we should do this experiment must depend on what the correct prior is, right? On the other hand, if we had the correct prior, we wouldn't need a "minimal required exploration rate". The agent would just explore/exploit optimally according to the prior.
In theory, changing the exploration rate and changing the prior are equivalent. I think that it might be easier to decide upon an exploration rate that gives a good result for generic priors, than to be sure that generic priors have good exploration rates. But this is just an impression.
Not really. Standard AIXI is completely deterministic, while the usual exploration strategies for reinforcement learning, such as ɛ-greedy and soft-max, are stochastic.
By changing the prior, you can make an AIXI agent explore more if it receives one set of inputs and also explore less if it receives another set of inputs. You can't do this by changing an "exploration rate", unless you're using some technical definition where it's not a scalar number?
Given arbitrary computing power and full knowledge of the actual environment, these are equivalent. But, as you point out, in practice they're going to be different. For us, something simple like a "exploration rate" is probably more understandable for what the AIXI's actions will look like.