One thing to keep in mind is that time cut-offs will usually rule out our own universe as a hypothesis. Our universe is insanely compute inefficient.
So the “hypotheses” inside your inductor won’t actually end up corresponding to what we mean by a scientific hypothesis. The only reason this inductor will work at all is that it’s done a brute force search over a huge space of programs until it finds one that works. Plausibly it’ll just find a better efficient induction algorithm, with a sane prior.
That’s fine. I just want a computable predictor that works well. This one does.
Also, scientific hypotheses in practice aren’t actually simple code for a costly simulation we run. We use approximations and abstractions to make things cheap. Most of our science outside particle physics is about finding more effective approximations for stuff.
Edit: Actually, I don’t think this would yield you a different general predictor as the program dominating the posterior. General inductor program P1 running program P2 is pretty much never going to be the shortest implementation of P2.
You also want one that generalises well, and doesn’t do preformative predictions, and doesn’t have goals of its own. If your hypotheses aren’t even intended to be reflections of reality, how do we know these properties hold?
Also, scientific hypotheses in practice aren’t actually simple code for a costly simulation we run. We use approximations and abstractions to make things cheap. Most of our science outside particle physics is actually about finding more effective approximate models for things in different regimes.
When we compare theories, we don’t consider the complexity of all the associated approximations and abstractions. We just consider the complexity of the theory itself.
E.g. the theory of evolution isn’t quite code for a costly simulation. But it can be viewed as set of statements about such a simulation. And the way we compare the theory of evolution to alternatives doesn’t involve comparing the complexity of the set of approximations we used to work out the consequences of each theory.
Edit to respond to your edit: I don’t see your reasoning, and that isn’t my intuition. For moderately complex worlds, it’s easy for the description length of the world to be longer than the description length of many kinds of inductor.
You also want one that generalises well, and doesn’t do preformative predictions, and doesn’t have goals of its own. If your hypotheses aren’t even intended to be reflections of reality, how do we know these properties hold?
Because we have the prediction error bounds.
When we compare theories, we don’t consider the complexity of all the associated approximations and abstractions. We just consider the complexity of the theory itself.
E.g. the theory of evolution isn’t quite code for a costly simulation. But it can be viewed as set of statements about such a simulation. And the way we compare the theory of evolution to alternatives doesn’t involve comparing the complexity of the set of approximations we used to work out the consequences of each theory.
To respond to your edit: I don’t see your reasoning, and that isn’t my intuition. For moderately complex worlds, it’s easy for the description length of the world to be longer than the description length of many kinds of inductor.
Because we have the prediction error bounds.
Not ones that can rule out any of those things. My understanding is that the bounds are asymptotic or average-case in a way that makes them useless for this purpose. So if a mesa-inductor is found first that has a better prior, it’ll stick with the mesa-inductor. And if it has goals, it can wait as long as it wants to make a false prediction that helps achieve its goals. (Or just make false predictions about counterfactuals that are unlikely to be chosen).
If I’m wrong then I’d be extremely interested in seeing your reasoning. I’d maybe pay $400 for a post explaining the reasoning behind why prediction error bounds rule out mesa-optimisers in the prior.
The bound is the same one you get for normal Solomonoff induction, except restricted to the set of programs the cut-off induction runs over. It’s a bound on the total expected error in terms of CE loss that the predictor will ever make, summed over all datapoints.
Look at the bound for cut-off induction in that post I linked, maybe? Hutter might also have something on it.
Can also discuss on a call if you like.
Note that this doesn’t work in real life, where the programs are not in fact restricted to outputting bit string predictions and can e.g. try to trick the hardware they’re running on.
Yeah I know that bound, I’ve seen a very similar one. The problem is that mesa-optimisers also get very good prediction error when averaged over all predictions. So they exist well below the bound. And they can time their deliberately-incorrect predictions carefully, if they want to survive for a long time.
One thing to keep in mind is that time cut-offs will usually rule out our own universe as a hypothesis. Our universe is insanely compute inefficient.
So the “hypotheses” inside your inductor won’t actually end up corresponding to what we mean by a scientific hypothesis. The only reason this inductor will work at all is that it’s done a brute force search over a huge space of programs until it finds one that works. Plausibly it’ll just find a better efficient induction algorithm, with a sane prior.
That’s fine. I just want a computable predictor that works well. This one does.
Also, scientific hypotheses in practice aren’t actually simple code for a costly simulation we run. We use approximations and abstractions to make things cheap. Most of our science outside particle physics is about finding more effective approximations for stuff.
Edit: Actually, I don’t think this would yield you a different general predictor as the program dominating the posterior. General inductor program P1 running program P2 is pretty much never going to be the shortest implementation of P2.
You also want one that generalises well, and doesn’t do preformative predictions, and doesn’t have goals of its own. If your hypotheses aren’t even intended to be reflections of reality, how do we know these properties hold?
When we compare theories, we don’t consider the complexity of all the associated approximations and abstractions. We just consider the complexity of the theory itself.
E.g. the theory of evolution isn’t quite code for a costly simulation. But it can be viewed as set of statements about such a simulation. And the way we compare the theory of evolution to alternatives doesn’t involve comparing the complexity of the set of approximations we used to work out the consequences of each theory.
Edit to respond to your edit: I don’t see your reasoning, and that isn’t my intuition. For moderately complex worlds, it’s easy for the description length of the world to be longer than the description length of many kinds of inductor.
Because we have the prediction error bounds.
Yes.
To respond to your edit: I don’t see your reasoning, and that isn’t my intuition. For moderately complex worlds, it’s easy for the description length of the world to be longer than the description length of many kinds of inductor.
Not ones that can rule out any of those things. My understanding is that the bounds are asymptotic or average-case in a way that makes them useless for this purpose. So if a mesa-inductor is found first that has a better prior, it’ll stick with the mesa-inductor. And if it has goals, it can wait as long as it wants to make a false prediction that helps achieve its goals. (Or just make false predictions about counterfactuals that are unlikely to be chosen).
If I’m wrong then I’d be extremely interested in seeing your reasoning. I’d maybe pay $400 for a post explaining the reasoning behind why prediction error bounds rule out mesa-optimisers in the prior.
The bound is the same one you get for normal Solomonoff induction, except restricted to the set of programs the cut-off induction runs over. It’s a bound on the total expected error in terms of CE loss that the predictor will ever make, summed over all datapoints.
Look at the bound for cut-off induction in that post I linked, maybe? Hutter might also have something on it.
Can also discuss on a call if you like.
Note that this doesn’t work in real life, where the programs are not in fact restricted to outputting bit string predictions and can e.g. try to trick the hardware they’re running on.
Yeah I know that bound, I’ve seen a very similar one. The problem is that mesa-optimisers also get very good prediction error when averaged over all predictions. So they exist well below the bound. And they can time their deliberately-incorrect predictions carefully, if they want to survive for a long time.