Clustered Sparse Bayesian Learning

Many machine learning and signal processing tasks involve computing sparse representations using an overcomplete set of features or basis vectors, with compressive sensing-based applications a notable example. While traditionally such problems have been solved individually for different tasks, this strategy ignores strong correlations that may be present in real world data. Consequently there has been a push to exploit these statistical dependencies by jointly solving a series of sparse linear inverse problems. In the majority of the resulting algorithms however, we must a priori decide which tasks can most judiciously be grouped together. In contrast, this paper proposes an integrated Bayesian framework for both clustering tasks together and subsequently learning optimally sparse representations within each cluster. While probabilistic models have been applied previously to solve these types of problems, they typically involve a complex hierarchical Bayesian generative model merged with some type of approximate inference, the combination of which renders rigorous analysis of the underlying behavior virtually impossible. On the other hand, our model subscribes to concrete motivating principles that we carefully evaluate both theoretically and empirically. Importantly, our analyses take into account all approximations that are involved in arriving at the actual cost function to be optimized. Results on synthetic data as well as image recovery from compressive measurements show improved performance over existing methods.