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arXiv · 2602.15341

Testing Monotonicity of Real-Valued Functions on DAGs

Yuichi Yoshida
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Abstract

We study monotonicity testing of real-valued functions on directed acyclic graphs (DAGs) with $n$ vertices. Let $m$ and $\ell$ be the numbers of edges in the transitive reduction and the transitive closure, respectively. For $1\le c\le d\le2$, define $u(c,d):=\min\left\{\frac12,\frac c3,\frac{c+d}{2}-1\right\}$. We show that every family of DAGs with $m=n^{c+o(1)}$ and $\ell=n^{d+o(1)}$ admits, for every fixed $\varepsilon\in(0,1)$, a non-adaptive tester with one-sided error that uses $O_\varepsilon(n^{u(c,d)+o(1)})$ queries. Conversely, we show that for every sufficiently small fixed $\varepsilon>0$ and every fixed $(c,d)$, there are families of DAGs satisfying $m=n^{c+o(1)}$ and $\ell=n^{d+o(1)}$ on which every randomized non-adaptive tester, even with two-sided error, requires $n^{u(c,d)-o(1)}$ queries, making the upper bound tight up to a factor $n^{o(1)}$. Our main technical contribution is a lower-bound technique based on Ruzsa--Szemer\'edi families of positive matchings.

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Yuichi Yoshida. 2026-02-17. Testing Monotonicity of Real-Valued Functions on DAGs. https://arxiv.org/abs/2602.15341

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