Using Lower Bounds During Dynamic BDD Minimization

Ordered Binary Decision Diagrams BDDs are a data structure for representation and manipulation of Boolean functions often applied in VLSI CAD. The choice of the variable ordering largely in uences the size of the BDD; its size may vary from linear to exponential. The most successful methods for nding good orderings are based on dynamic variable reordering, i.e. exchanging of neighboring variables. This basic operation has been used in various variants, like sifting and window permutation. In this paper we show that lower bounds computed during the minimization process can speed up the computation signi cantly. First, lower bounds are studied from a theoretical point of view. Then these techniques are incorporated in dynamic minimization algorithms. By the computation of good lower bounds large parts of the search space can be pruned resulting in very fast computations. Experimental results are given to demonstrate the e ciency of our approach.

• Type: Conference
• Year: 1999
• Where: DAC
• Authors: Rolf Drechsler, Wolfgang Günther
• Keywords: Binary Decision Diagrams, Computer Architecture, DAC 1999, Dynamic Variable Reordering, Lower Bounds