In recent times the cavity method, a statistical physics-inspired heuristic, has been successful in conjecturing computational thresholds that have been rigorously confirmed -- such as for community detection in the sparse regime of the stochastic block model. Inspired by this, we investigate the predictions made by the cavity method for the algorithmic problems of detecting and recovering a planted signal in a general model of sparse random graphs. The model we study generalizes the well-understood case of the stochastic block model, the less well understood case of random constraint satisfaction problems with planted assignments, as well as "semi-supervised" variants of these models. Our results include: (i) a conjecture about a precise criterion for when the problems of detection and recovery should be algorithmically tractable arising from a heuristic analysis of when a particular fixed point of the belief propagation algorithm is stable; (ii) a rigorous polynomial-time algorithm for the problem of detection: distinguishing a graph with a planted signal from one without; (iii) a rigorous polynomial-time algorithm for the problem of recovery: outputting a vector that correlates with the planted signal significantly better than a random guess would. The rigorous algorithms are based on the spectra of matrices that arise as the derivatives of the belief propagation update rule. An interesting unanswered question raised is that of obtaining evidence of computational hardness for convex relaxations whenever hardness is predicted by the cavity method.
翻译:近些年来,由统计物理所启发的外观学方法,即一种由统计物理所启发的外观学,成功地预测了严格证实的计算阈值 -- -- 例如,在随机区块模型的稀疏制度下,社区检测。受此启发,我们调查了在稀散随机图总模型中检测和恢复植入信号的算法问题的剖析法方法的预测。我们研究的模型概括了人们所熟知的分流区块模型模型案例、在布置任务中随机限制满意度问题以及这些模型的“半监督”变异体。我们的结果包括:(一) 关于检测和复原问题应何时在逻辑学上具有可理解性的准确标准的推测。我们研究的模型概括了对特定固定的传动图谱值稳定时产生的逻辑问题。 (二) 精确的多元时间算法用于检测问题的精确度:用一个与一个没有的刻度信号区分出式信号与一个没有的相区别;(三) 精确的多数值算法测算法对于恢复的精确度的精确度,其精确性测算法是:一个基于精确的递解算法的递增变现的变式规则的序列的序列的精确性,其结果的逻辑是,一个可靠的递增变压的序列变压的必然的变压。