Boolean satisfiability and equivalence checking using general binary decision diagrams

It is shown how general binary decision diagrams (BDDs), i.e., BDDs where input variables are allowed to appear multiple times along any path in the BDD, can be used to check for Boolean satisfiability. This satisfiability checking strategy is based on an input smoothing operation on general BDDs. Various input smoothing strategies for general BDDs are developed. In order to verify the equivalence of two functions f/sub 1/ and f/sub 2/, f/sub 1/(+)f/sub 2/ is checked for satisfiability. Using general BDDs different implementations of a 16*16 multiplier, a modified Achilles' heel function and a complex add-shift function were verified. It was not possible to construct OBDDs for any of the three functions.>