TreeFlow: Going beyond Tree-based Gaussian Probabilistic Regression

The tree-based ensembles are known for their outstanding performance for classification and regression problems characterized by feature vectors represented by mixed-type variables from various ranges and domains. However, considering regression problems, they are primarily designed to provide deterministic responses or model the uncertainty of the output with a Gaussian distribution. In this work, we introduce TreeFlow, the tree-based approach that combines the benefits of using tree ensembles with capabilities of modeling flexible probability distributions using normalizing flows. The main idea of the solution is to use a tree-based model as a feature extractor and combine it with a conditional variant of normalizing flow. Consequently, our approach is capable of modeling complex distributions for the regression outputs. We evaluate the proposed method on challenging regression benchmarks with varying volume, feature characteristics, and target dimensionality. We obtain the SOTA results on datasets with non-gaussian target distributions and competitive results on gaussian ones compared to tree-based regression baselines.