Boolean matching for large libraries

Boolean matching tackles the problem whether a subcircuit of a boolean network can be substituted by a cell from a cell library. In previous approaches each pair of a subcircuit and a cell is tested for NPN equivalence. This becomes very expensive if the cell library is large. In our approach the time complexity for matching a subcircuit against a library L is almost independent of the size of L. CPU time also remains small for matching a subcircuit against the huge set of functions obtained by bridging and fixing cell inputs; but the use of these functions in technology mapping is very profitable. Our method is based on a canonical representative for each NPN equivalence class. We show how this representative can be computed efficiently and how it can be used for matching a boolean function against a set of library functions.