### Tim Genewein

Information-optimal hierarchies for inference and decision-making

Bosch Center for Artificial Intelligence
Stuttgart - Renningen, Germany

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# Paper by F. Leibfried: Bounded rational decision-making in feedforward neural networks

Felix Leibfried just published a very interesting application of the information-theoretic principle for bounded rationality to feedforward neural networks (including convolutional neural networks). This work will be presented in a plenary talk at UAI 2016.

In a nutshell, the information-theoretic optimality principle (similar to the rate-distortion principle, see here) was used to derive a gradient-based on-line update rule to learn the parameters of a neural network. In the principle, gains in utility must be traded off against the computational cost that these gains incur

where a parametric model $p_\theta(a\vert w)$ is used to describe the stochastic mapping from an input $w$ to an output $a$. In the paper, Felix shows how to derive a gradient-ascent rule for finding a (locally) optimal $\theta$. Then, the paper shows how to apply the same principle and derive an on-line gradient-based update rule when using a feedforward neural network for the parametric model. Interestingly, the result is an update-rule very similar to the (well-known) error-backpropagation with an additional regularization-term that results from the mutual information constraint (that formalizes limited computational capacity).

This result adds an interesting angle to the notion of limited computational resources: an alternative way to interpret computational limitations is to view them as a regularizer, that (sort of) artificially imposes computational limitations in order to be robust. This regularizer reflects the computational limitation that results from having small sample sizes - with an infinitely large sample size, corresponding to no computational limitation, the regularizer is not needed. However, under limited sample size (limited information to update the parameters), a regularizer “emulates” limited computational resources that reflect the lack of rich parameter-update information.

The paper concludes by showing simulations that apply the learning rule to a regular multi-layer perceptron as well as a convolutional neural network on the MNIST data set.