On variable ordering of binary decision diagrams for the application of multi-level logic synthesis

Develops multi-level logic minimization programs using binary decision diagram (BDD). The authors present variable ordering methods of BDD. The variable ordering algorithm for two-level circuits is based on cover patterns and selects most binate variables first, and the one for multi-level circuits is based on depth first traverse of circuits. In both cases, the acquired variable orderings are optimized by exchanging a variable with its neighbor in the ordering