Additive estimates of the permanent using Gaussian fields
Tantrik Mukerji, Wei-Shih Yang
TL;DR
This work addresses the problem of additively estimating the permanent $\mathrm{perm}(A)$ of a real matrix by embedding $A$ into a Gaussian field and exploiting Wick calculus. The authors show that $\mathrm{perm}(A)$ equals the expectation of a product of $2M$ Gaussian variables under a carefully chosen covariance $C$, and they estimate it via the empirical mean of products across $N$ samples, achieving a polynomial-time bound $P(|S_N-\mathrm{perm}(A)|>t)$ with a complexity of $O(M^{3}+M^{2}N+MN)$. A central contribution is the universal $2M$-dimensional Gaussian embedding for any $A$ and a semidefinite-programming framework to choose (and possibly modify) the covariance to minimize variance, yielding additive FPRAS in favorable regimes and connections to Max-Cut and cut-norms. The paper thus provides a novel, geometry- and graph-theory-inspired approach to permanent approximation that can offer improvements over Gurvits for certain matrix classes and opens avenues for further exploration of Gaussian embeddings in combinatorial counting problems.
Abstract
We present a randomized algorithm for estimating the permanent of an $M \times M$ real matrix $A$ up to an additive error. We do this by viewing the permanent $\mathrm{perm}(A)$ of $A$ as the expectation of a product of centered joint Gaussian random variables with a particular covariance matrix $C$. The algorithm outputs the empirical mean $S_{N}$ of this product after sampling $N$ times. Our algorithm runs in total time $O(M^{3} + M^{2}N + MN)$ with failure probability \begin{equation*} P(|S_{N}-\text{perm}(A)| > t) \leq \frac{3^{M}}{t^{2}N} \prod^{2M}_{i=1} C_{ii}. \end{equation*} In particular, we can estimate $\mathrm{perm}(A)$ to an additive error of $ε\bigg(\sqrt{3^{2M}\prod^{2M}_{i=1} C_{ii}}\bigg)$ in polynomial time. We compare to a previous procedure due to Gurvits. We discuss how to find a particular $C$ using a semidefinite program and a relation to the Max-Cut problem and cut-norms.
