,
Yucheng Fu
Creative Commons Attribution 4.0 International license
The f-divergence is a fundamental notion that measures the difference between two distributions. In this paper, we study the problem of approximating the f-divergence between two Ising models, which is a generalization of recent work on approximating the TV-distance. Given two Ising models ν and μ, which are specified by their interaction matrices and external fields, the problem is to approximate the f-divergence D_f (ν ‖ μ) within an arbitrary relative error e^{±ε}. For χ^α-divergence with a constant integer α, we establish both algorithmic and hardness results. The algorithm works in a parameter regime that matches the hardness result. Our algorithm can be extended to other f-divergences such as α-divergence, Kullback-Leibler divergence, Rényi divergence, Jensen-Shannon divergence, and squared Hellinger distance.
@InProceedings{feng_et_al:LIPIcs.ITCS.2026.59,
author = {Feng, Weiming and Fu, Yucheng},
title = {{On Approximating the f-Divergence Between Two Ising Models}},
booktitle = {17th Innovations in Theoretical Computer Science Conference (ITCS 2026)},
pages = {59:1--59:23},
series = {Leibniz International Proceedings in Informatics (LIPIcs)},
ISBN = {978-3-95977-410-9},
ISSN = {1868-8969},
year = {2026},
volume = {362},
editor = {Saraf, Shubhangi},
publisher = {Schloss Dagstuhl -- Leibniz-Zentrum f{\"u}r Informatik},
address = {Dagstuhl, Germany},
URL = {https://drops.dagstuhl.de/entities/document/10.4230/LIPIcs.ITCS.2026.59},
URN = {urn:nbn:de:0030-drops-253469},
doi = {10.4230/LIPIcs.ITCS.2026.59},
annote = {Keywords: Ising model, f-divergence, approximation algorithms, randomized algorithms}
}