An Efficient New Junction Tree Architecture

The Hugin and Shafer-Shenoy architectures are variations on the junction tree algorithm which tradeoff space and time complexities in different ways. The Hugin architecture is faster than that of Shafer-Shenoy but at the cost of a greater space complexity. This paper presents a new architecture which, in the cases where there exist relatively large vertices of the junction tree with high degree (or with many small corresponding factors), is significantly faster than Hugin propagation. The time complexity of the new architecture is never more than a logarithmic factor more than that of Hugin propagation. Like Shafer-Shenoy propagation, the space complexity of the new architecture is only exponential in the size of the largest factor or separator, rather than being exponential in the size of the largest vertex as in Hugin propagation.