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Neural Networks Are Decision Trees (arxiv.org)
34 points by todsacerdoti on Oct 16, 2022 | hide | past | pdf | 9 comments on HN

In plain words: Any neural network can be rewritten exactly as a decision tree, with the same outputs and no loss of accuracy, making its decisions easier to follow. The conversion works for fully connected and convolutional networks, and for small ones the tree can run faster.

Abstract · Neural Networks are Decision Trees

In this manuscript, we show that any neural network with any activation function can be represented as a decision tree. The representation is equivalence and not an approximation, thus keeping the accuracy of the neural network exactly as is. We believe that this work provides better understanding of neural networks and paves the way to tackle their black-box nature. We share equivalent trees of some neural networks and show that besides providing interpretability, tree representation can also achieve some computational advantages for small networks. The analysis holds both for fully connected and convolutional networks, which may or may not also include skip connections and/or normalizations.

Caglar Aytekin
arXiv:2210.05189 · cs.LG · submitted Oct 11, 2022 · updated Oct 25, 2022
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Also discussed: Oct 2022 (4 points, 2 comments) · Oct 2022 (4 points, 0 comments) · Oct 2022 (3 points, 0 comments)

  This equivalence shows that neural networks are indeed interpretable by design and makes the \textit{black-box} understanding obsolete
Show me the decision tree for a big classifier trained on imagenet, and let's see if it's interoperable
How about the decision tree for even a simple recurrent NN.
Who says Decision Trees aren't black boxes? That was one of the first exercises taught after DTs: Decision Trees aren't always explainable. You need to prune them before getting anything useful
This is something I already suspected since you can encode piece-wise linear function-based neural networks (of a reasonable size) as mixed-integer problems (MIP). Since MIP is NP-complete, that means you could also translate the neural network more painfully into SAT, giving you all the interpretability you could possible want...

Except I'm not too sure how "interpretable" the results really would be in most cases. What questions would you pose to an ML model recognizing images or audio?

Second order questions (i.e. get a really good machine): What is the minimal difference in input needed for class A to be recognized as class B? What the (an) input closest to all classes and what is the distance to each? Are there weights for this smaller NN that remain equivalent to the given NN?
That makes a lot of sense, thanks!
Isn't this a tautology to the tune of "a program running on a Turing machine is a program running on a Turing machine"?
Read the paper, it's quite short and sweet (though NN papers do have a lot of subscripts and superscipts)

Basically yes, it was known that we can always do this. But apparently until now no one gave an algorithm to do so. I think it would probably be difficult to come up with a similar algo for sofmax

Here’s a list of 50,000 decision rules based on a sparse vector model of the universe = “interpretable”?