Enhancing Simple Models by Exploiting What They Already Know
This addresses the need for interpretable, memory-efficient, and environmentally friendly models in machine learning, though it is incremental as it builds on prior work by incorporating per-sample hardness estimates and generalizing probe concepts.
The paper tackles the problem of improving the performance of simple models like decision trees or shallow networks by reweighting training data using information from complex models, achieving competitive or superior results in 16 out of 27 cases on datasets including UCI and CIFAR-10, and in some instances approaching the performance of complex models.
There has been recent interest in improving performance of simple models for multiple reasons such as interpretability, robust learning from small data, deployment in memory constrained settings as well as environmental considerations. In this paper, we propose a novel method SRatio that can utilize information from high performing complex models (viz. deep neural networks, boosted trees, random forests) to reweight a training dataset for a potentially low performing simple model of much lower complexity such as a decision tree or a shallow network enhancing its performance. Our method also leverages the per sample hardness estimate of the simple model which is not the case with the prior works which primarily consider the complex model's confidences/predictions and is thus conceptually novel. Moreover, we generalize and formalize the concept of attaching probes to intermediate layers of a neural network to other commonly used classifiers and incorporate this into our method. The benefit of these contributions is witnessed in the experiments where on 6 UCI datasets and CIFAR-10 we outperform competitors in a majority (16 out of 27) of the cases and tie for best performance in the remaining cases. In fact, in a couple of cases, we even approach the complex model's performance. We also conduct further experiments to validate assertions and intuitively understand why our method works. Theoretically, we motivate our approach by showing that the weighted loss minimized by simple models using our weighting upper bounds the loss of the complex model.