论文标题

对称二进制感知模型中的算法和障碍

Algorithms and Barriers in the Symmetric Binary Perceptron Model

论文作者

Gamarnik, David, Kızıldağ, Eren C., Perkins, Will, Xu, Changji

论文摘要

对称的二进制perceptron($ \ texttt {sbp} $)表现出戏剧性的统计到计算差距:已知有效算法发现解决方案的密度远低于解决方案的阈值。此外,$ \ texttt {sbp} $具有惊人的结构属性:几乎所有正面约束密度几乎所有的解决方案都是“完全冷冻的”单例,由大吊装距离\ cite {perkins2021frozen,abbe2021proface}。这表明找到$ \ texttt {sbp} $的解决方案可能在计算上很棘手。同时,$ \ texttt {sbp} $确实以低密度的方式允许多项式搜索算法。在\ cite {baldassi2020 clustering}中提出了对这个难题的猜想解释:有效的算法在冻结中成功地找到了大尺寸的成倍稀有簇。但是,最近发现,即使在已知有效算法\ cite {abbe2021binary}的极限范围的所有亚临界密度下,这种罕见的大簇也存在。因此,该模型表现出的统计到计算差距的驱动力仍然是一个谜。 在本文中,我们进行了不同的景观分析,以解释该问题的算法障碍性。我们表明,在足够高的密度下,$ \ texttt {sbp} $展示了多重叠间隙属性($ m- $ ogp),这是一种复杂的几何属性,已知是大型算法的严格障碍。我们的分析表明,$ m- $ ogp阈值(a)远低于满足性阈值; (b)将最著名的算法阈值与对数因素匹配为$ m \至\ infty $。然后,我们证明,$ m- $ ogp将$ \ texttt {sbp} $上面的稳定算法的类排除。我们推测$ m \ to \ infty $限制的$ M $ -OGP阈值标志着该问题的算法阈值。

The symmetric binary perceptron ($\texttt{SBP}$) exhibits a dramatic statistical-to-computational gap: the densities at which known efficient algorithms find solutions are far below the threshold for the existence of solutions. Furthermore, the $\texttt{SBP}$ exhibits a striking structural property: at all positive constraint densities almost all of its solutions are 'totally frozen' singletons separated by large Hamming distance \cite{perkins2021frozen,abbe2021proof}. This suggests that finding a solution to the $\texttt{SBP}$ may be computationally intractable. At the same time, the $\texttt{SBP}$ does admit polynomial-time search algorithms at low enough densities. A conjectural explanation for this conundrum was put forth in \cite{baldassi2020clustering}: efficient algorithms succeed in the face of freezing by finding exponentially rare clusters of large size. However, it was discovered recently that such rare large clusters exist at all subcritical densities, even at those well above the limits of known efficient algorithms \cite{abbe2021binary}. Thus the driver of the statistical-to-computational gap exhibited by this model remains a mystery. In this paper, we conduct a different landscape analysis to explain the algorithmic tractability of this problem. We show that at high enough densities the $\texttt{SBP}$ exhibits the multi Overlap Gap Property ($m-$OGP), an intricate geometrical property known to be a rigorous barrier for large classes of algorithms. Our analysis shows that the $m-$OGP threshold (a) is well below the satisfiability threshold; and (b) matches the best known algorithmic threshold up to logarithmic factors as $m\to\infty$. We then prove that the $m-$OGP rules out the class of stable algorithms for the $\texttt{SBP}$ above this threshold. We conjecture that the $m \to \infty$ limit of the $m$-OGP threshold marks the algorithmic threshold for the problem.

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