Crossposted from my blog.

One thing I worry about sometimes is people writing code with optimisers in it, without realising that that's what they were doing. An example of this: suppose you were doing deep reinforcement learning, doing optimisation to select a controller (that is, a neural network that takes a percept and returns an action) that generated high reward in some environment. Alas, unknown to you, this controller actually did optimisation itself to select actions that score well according to some metric that so far has been closely related to your reward function. In such a scenario, I'd be wary about your deploying that controller, since the controller itself is doing optimisation which might steer the world into a weird and unwelcome place.

In order to avoid such scenarios, it would be nice if one could look at an algorithm and determine if it was doing optimisation. Ideally, this would involve an objective definition of optimisation that could be checked from the source code of the algorithm, rather than something like "an optimiser is a system whose behaviour can't usefully be predicted mechanically, but can be predicted by assuming it near-optimises some objective function", since such a definition breaks down when you have the algorithm's source code and can compute its behaviour mechanically.

You might think about optimisation as follows: a system is optimising some objective function to the extent that that objective function attains much higher values than would be attained if the system didn't exist, or were doing some other random thing. This type of definition includes those put forward by Yudkowsky and Oesterheld. However, I think there are crucial counterexamples to this style of definition.

Firstly, consider a lid screwed onto a bottle of water. If not for this lid, or if the lid had a hole in it or were more loose, the water would likely exit the bottle via evaporation or being knocked over, but with the lid, the water stays in the bottle much more reliably than otherwise. As a result, you might think that the lid is optimising the water remaining inside the bottle. However, I claim that this is not the case: the lid is just a rigid object designed by some optimiser that wanted water to remain inside the bottle.

This isn't an incredibly compelling counterexample, since it doesn't qualify as an optimiser according to Yudkowsky's definit

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