Comment on MIRI's Approach

Fri, 31 Jul 2015 04:00:02 GMT

Thanks for the clarifications - I'll make this short.

Judea Pearl (and a whole host of others) showed up, formalized probabilistic graphical models, related them to Bayesian inference, and suddenly a whole class of ad-hoc solutions were superseded.

Probabilistic graphical models were definitely a key theoretical development, but they hardly swept the field of expert systems. From what I remember, in terms of practical applications, they immediately replaced or supplemented expert systems in only a few domains - such as medical diagnostic systems. Complex ad hoc expert systems continued to dominate unchallenged in most fields for decades: in robotics, computer vision, speech recognition, game AI, fighter jets, etc etc basically everything important. As far as I am aware the current ANN revolution is truly unique in that it is finally replacing expert systems across most of the board - although there are still holdouts (as far as I know most robotic controllers are still expert systems, as are fighter jets, and most Go AI systems).

The ANN solutions are more complex than the manually crafted expert systems they replace - but the complexity is automatically generated. The code the developers actually need to implement and manage is vastly simpler - this is the great power and promise of machine learning.

Here is a simple general truth - the Occam simplicity prior does imply that simpler hypotheses/models are more likely, but for any simple model there are an infinite family of approximations to that model of escalating complexity. Thus more efficient approximations naturally tend to have greater code complexity, even though they approximate a much simpler model.

My claim is that there are other steps such as those that haven't been made yet, that there are tools on the order of "causal graphical models" that we are missing.

Well, that would be interesting.

I'm not sure whether your view is of the form "actually the programmer of the future would say "I don't know how it's building a model of the world either, it's just a big neural net that I trained for a long time"" or whether it's of the form "actually we do know how to set up that system [multi-level model] already", or whether it's something else entirely. But if it's the second one, then by all means, please tell :-)

Anyone who has spent serious time working in graphics has also spent serious time thinking about how to create the matrix - if given enough computer power. If you got say a thousand of the various brightest engineers in different simulation related fields, from physics to graphics, and got them all working on a large mega project with huge funds it could probably be implemented today. You'd start with a hierarchical/multi-resolution modelling graph - using say octrees or kdtrees over voxel cells, and a general set of hierarchical bidirectional inference operators for tracing paths and interactions.

To make it efficient, you need a huge army of local approximation models for different phenomena at different scales - low level quantum codes just in case, particle level codes, molecular bio codes, fluid dynamics, rigid body, etc etc. It's a sea of codes with decision tree like code to decide which models to use where and when.

Of course with machine learning we could automatically learn most of those codes - which suddenly makes it more tractable. And then you could use that big engine as your predictive world model, once it was trained.

The problem is to plan anything worthwhile you need to simulate human minds reasonably well, which means to be useful the sim engine would basically need to infer copies of everyone's minds . . ..

And if you can do that, then you already have brain based AGI!

So I expect that the programmer from the future will say - yes at the low level we use various brain-like neural nets, and various non-brain like neural nets or learned virtual circuits, some operating over explicit space-time graphs. In all cases we have pretty detailed knowledge of what the circuits are doing - here take a look at that last goal update that just propagated in your left anterior prefrontal cortex . ..

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