Fast hierarchical implementation of sequential tree-reweighted belief propagation for probabilistic inference

Maximum a posteriori probability (MAP) inference on Markov random fields (MRF) is the basis of many computer vision applications. Sequential tree-reweighted belief propagation (TRW-S) has been shown to provide very good inference quality and strong convergence properties. However, software TRW-S solvers are slow due to the algorithm's high computational requirements. A state-of-the-art FPGA implementation has been developed recently, which delivers substantial speedup over software. In this paper, we improve upon the TRW-S algorithm by using a multi-level hierarchical MRF formulation. We demonstrate the benefits of Hierarchical-TRW-S over TRW-S, and incorporate the proposed improvements on a Convey HC-1 CPU-FPGA hybrid platform. Results using four Middlebury stereo vision benchmarks show a 21% to 53% reduction in inference time compared with the state-of-the-art TRW-S FPGA implementation. To the best of our knowledge, this is the fastest hardware implementation of TRW-S reported so far.