Revisiting Forest Proximities via Sparse Leaf-Incidence Kernels

Fuente: arXiv
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Autores principales: Aumon, Adrien, Wolf, Guy, Moon, Kevin R., Rhodes, Jake S.
Formato: Preprint
Publicado: 2026
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author Aumon, Adrien
Wolf, Guy
Moon, Kevin R.
Rhodes, Jake S.
author_facet Aumon, Adrien
Wolf, Guy
Moon, Kevin R.
Rhodes, Jake S.
contents Decision forests induce supervised similarities through the partition structure of their trees. Yet forest proximity computation is still often treated as a quadratic operation in the number of samples, which limits scalability and restricts broader use in kernel and representation-learning pipelines. We introduce a unified view of leaf-collision forest proximities through a class of Separable Weighted Leaf-Collision (SWLC) kernels, showing that most existing proximities differ only in their weighting scheme while sharing a common sparse leaf-incidence structure. This yields an explicit leaf-space representation that clarifies their kernel interpretation and leads to an exact finite-sample sparse factorization of the proximity matrix, avoiding an explicit all-pairs comparison and reducing computation to sparse linear algebra over leaf collisions. We implement this framework in a memory-efficient Python library and show, both theoretically and empirically, that exact kernel computation scales near-linearly in time and memory under standard forest regimes. Benchmarks verify the predicted scaling behavior in practice across datasets, proximity definitions, and forest settings, and show that the resulting sparse leaf-space representation can also be used directly for fast task-aware embedding.
format Preprint
id arxiv_https___arxiv_org_abs_2601_02735
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle Revisiting Forest Proximities via Sparse Leaf-Incidence Kernels
Aumon, Adrien
Wolf, Guy
Moon, Kevin R.
Rhodes, Jake S.
Machine Learning
Data Structures and Algorithms
Performance
Decision forests induce supervised similarities through the partition structure of their trees. Yet forest proximity computation is still often treated as a quadratic operation in the number of samples, which limits scalability and restricts broader use in kernel and representation-learning pipelines. We introduce a unified view of leaf-collision forest proximities through a class of Separable Weighted Leaf-Collision (SWLC) kernels, showing that most existing proximities differ only in their weighting scheme while sharing a common sparse leaf-incidence structure. This yields an explicit leaf-space representation that clarifies their kernel interpretation and leads to an exact finite-sample sparse factorization of the proximity matrix, avoiding an explicit all-pairs comparison and reducing computation to sparse linear algebra over leaf collisions. We implement this framework in a memory-efficient Python library and show, both theoretically and empirically, that exact kernel computation scales near-linearly in time and memory under standard forest regimes. Benchmarks verify the predicted scaling behavior in practice across datasets, proximity definitions, and forest settings, and show that the resulting sparse leaf-space representation can also be used directly for fast task-aware embedding.
title Revisiting Forest Proximities via Sparse Leaf-Incidence Kernels
topic Machine Learning
Data Structures and Algorithms
Performance
url https://arxiv.org/abs/2601.02735