平方和反驳蕴含半随机CSP的植入解恢复
Sum-of-Squares Refutation Implies Planted Recovery for Semirandom CSPs
Arpon Basu, Andrew D. Lin, Peter Manohar
AI 速读 基于摘要
作者提出一种从半随机k-XOR的Sum-of-Squares反驳证书出发、隐式学习约束超图分解的算法,用于求解半随机植入CSP。
cs.DS
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We give a $n^{O(\ell)}$-time algorithm for solving semirandom planted instances of a $k$-ary Boolean constraint satisfaction problem (CSP) with $m \gtrsim \left(\frac{n}{\ell}\right)^{k/2} \ell \, \mathrm{polylog}(n)$ constraints, for any choice of the runtime parameter $\ell$. Up to $\mathrm{polylog}(n)$ factors, this matches the known runtime vs.\ number of constraints trade-off for refuting semirandom CSPs, as well as the trade-off for solving fully random planted CSPs. Prior work on designing algorithms for semirandom CSPs follows a high-level blueprint of decomposing the constraint hypergraph $\mathcal{H}$ of the instance into pieces, each with an explicit pseudorandom property that allows the standard algorithm for random CSPs to succeed on every piece. We depart considerably from this framework and instead implicitly \emph{learn} such a decomposition, without appealing directly to explicit properties such as expansion. More generally, we construct such a learning algorithm from the assumption that semirandom $k$-XOR has Sum-of-Squares certificates of refutation. This yields the broader implication that any Sum-of-Squares refutation algorithm for semirandom $k$-XOR gives a corresponding algorithm for solving semirandom planted CSPs, and instantiating this reduction with known Sum-of-Squares algorithms for refuting semirandom $k$-XOR gives our main algorithm. To the best of our knowledge, this is the first reduction from search to refutation for (semi)random CSPs.