在在线学习中用最少采样次数实现高精度序列聚类,适合数据量有限的场景。
Online Clustering of Data Sequences with Bandit Information
- 设计基于平均追踪的在线聚类算法,动态识别不同数据源的分组关系。
- 在多维高斯和指数族分布下,采样效率逼近理论最优极限。
- 算法兼具高精度与低计算开销,适合实时系统或资源受限环境。
我们研究在固定置信度设定下的多臂老虎机框架中对数据序列进行在线聚类的问题。共有 $M$ 个臂,每个臂独立同分布地生成来自未知参数分布的样本,这些臂根据真实参数间的距离构成 $K$ 个簇($K \le M$)。在多臂老虎机设置中,每次仅能选择一个臂进行采样。目标是在错误概率不超过 $\delta$ 的前提下,以最少的采样次数估计出臂的簇归属。该设定允许簇内臂具有非相同分布、向量参数、向量观测等复杂情况。我们提出并分析了平均追踪带限在线聚类(ATBOC)算法。对于多维高斯臂,ATBOC 在 $\delta \to 0$ 时为渐近阶最优,其期望采样复杂度最多为下界两倍;该性质也扩展至多维次高斯臂。对于单参数指数族臂,ATBOC 达到渐近最优,与下界一致。我们还提出了更高效的替代算法:基于上下界估计的聚类算法(LUCBBOC)和带限聚类消除算法(BOC-ELIM)。我们推导了各算法的计算复杂度,并通过仿真比较其每样本运行时间。结果显示,LUCBBOC 和 BOC-ELIM 的每样本运行时间低于 ATBOC,同时性能相当。所有算法均为 $\delta$-大概率正确,即停止时刻的聚类估计错误概率不超过 $\delta$。仿真验证了渐近最优性,并在合成与真实数据集上对比了所提算法与其他相关方法的表现。
原文摘要 · Abstract (English)
We study the problem of online clustering of data sequences in the multi-armed bandit (MAB) framework under the fixed-confidence setting. There are $M$ arms, each providing i.i.d. samples from a parametric distribution whose parameters are unknown. The $M$ arms form $K$ clusters based on the distance between the true parameters. In the MAB setting, one arm can be sampled at each time. The objective is to estimate the clusters of the arms using as few samples as possible from the arms, subject to an upper bound on the error probability. Our setting allows for: arms within a cluster to have non-identical distributions, vector parameter arms, vector observations, and $K \le M$ clusters. We propose and analyze the Average Tracking Bandit Online Clustering (ATBOC) algorithm. ATBOC is asymptotically order-optimal for multivariate Gaussian arms, with expected sample complexity grows at most twice as fast as the lower bound as $δ\rightarrow 0$, and this guarantee extends to multivariate sub-Gaussian arms. For single-parameter exponential family arms, ATBOC is asymptotically optimal, matching the lower bound. We also propose a computationally more efficient alternatives Lower and Upper Confidence Bound based Bandit Online Clustering Algorithm (LUCBBOC), and Bandit Online Clustering-Elimination (BOC-ELIM). We derive the computational complexity of the proposed algorithms and compare their per-sample runtime through simulations. LUCBBOC and BOC-ELIM require lower per-sample runtime than ATBOC while achieving comparable performance. All the proposed algorithms are $δ$-Probably correct, i.e., the error probability of cluster estimate at the stopping time is atmost $δ$. We validate the asymptotic optimality guarantees through simulations, and present the comparison of our proposed algorithms with other related work through simulations on both synthetic and real-world datasets.
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