Performance Improvement of Edge Expansion Technique for BDD-based Network Reliability Analysis

The network reliability analysis based on Binary Decision Diagram (BDD) consists of three steps: edge ordering, BDD generation and BDD evaluation. The BDD generation process using edge expansion technique should recursively decompose the network and construct the edge expansion subnet in a top-down manner. There is large number of useless or redundant subnets generated in this decomposition, which causes numerous inefficient computations. Thus, it is extremely important to optimize the edge expansion technique. In this paper, the notation of useless edge expansion and redundant edge expansion is formally defined. The original reason of them being created is identified, and the improvement algorithms based on graph traversal are used to eliminate all these inefficient edge expansion. According to the experimental data, compared with the unimproved BDD generation process, our proposal can dramatically reduce the running time and memory usage and makes possible the analysis of large network.