Combinatorial Characterizations of the Learnability of Conditional Distributions
Abstract
We study the PAC-learnability of function classes that map inputs to probability distributions over a finite space. The learner observes i.i.d. input-label pairs, with each label sampled from the conditional distribution of an unknown target hypothesis in the class. We measure learning through excess risk under a bounded proper loss that satisfies two mild assumptions. We introduce the \textbf{fatγNatarajan dimension}, which generalizes both fatγ and Natarajan dimension, and prove that its finiteness at every positive scale is necessary and sufficient for learnability. We also introduce a \textbf{fatγGraph} dimension extending the classical \gra dimension and establish inequalities comparing the two dimensions at different scales, leading to an equivalent characterization of learnability. Finally, we show that a distribution-valued function class is learnable if and only if each of its coordinate classes is learnable in the probabilistic concept model.
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BibTeX
@misc{dhanakshirur2026combinatorial,
title = {{Combinatorial Characterizations of the Learnability of Conditional Distributions}},
author = {Mihir Dhanakshirur and Ambuj Tewari},
howpublished = {arXiv},
year = {2026},
month = oct,
doi = {10.48550/arxiv.2610.31890},
eprint = {2610.31890},
archivePrefix = {arXiv},
url = {https://arxiv.org/abs/2610.31890},
note = {CC BY 4.0},
}
RIS
TY - UNPB
TI - Combinatorial Characterizations of the Learnability of Conditional Distributions
AU - Mihir Dhanakshirur
AU - Ambuj Tewari
PY - 2026
DA - 2026/10/22
PB - arXiv
DO - 10.48550/arxiv.2610.31890
UR - https://arxiv.org/abs/2610.31890
AB - We study the PAC-learnability of function classes that map inputs to probability distributions over a finite space. The learner observes i.i.d. input-label pairs, with each label sampled from the conditional distribution of an unknown target hypothesis in the class. We measure learning through excess risk under a bounded proper loss that satisfies two mild assumptions. We introduce the \textbf{fat_γNatarajan dimension}, which generalizes both fat_γ and Natarajan dimension, and prove that its finiteness at every positive scale is necessary and sufficient for learnability. We also introduce a \textbf{fat_γGraph} dimension extending the classical \gra dimension and establish inequalities comparing the two dimensions at different scales, leading to an equivalent characterization of learnability. Finally, we show that a distribution-valued function class is learnable if and only if each of its coordinate classes is learnable in the probabilistic concept model.
ER -