Technical Report No. 130 - Abstract

C. Scholl, B. Becker, A. Brogle
Solving the Multiple Variable Order Problem for Binary Decision Diagrams by Use of Dynamic Reordering Techniques

Reduced Ordered Binary Decision Diagrams (ROBDDs) gained widespread use in logic design verification, test generation, fault simulation, and logic s ynthesis [MWBS:88,Bry:92]. Since the size of an ROBDD heavily depends on the variable order used, there is a strong need to find variable orders that minimize the number of nodes in an ROBDD. In certain applications we have to cope with ROBDDs with different variable orders, whereas further manipulations of these ROBDDs require common variable orders. In this paper we solve the problem to transform ROBDDs with different variable orders into a good common variable order. To do so, we make use of dynamic variable ordering techniques.