Approaches to Permutation-Invariant Boolean Function Characterization

This paper introduces characteristic signatures for Boolean functions. The signatures exhibit little or no sensitivity to permutations of input variables. We use these signatures to develop a method of rapidly matching subcircuits with cells in a (large) library. The procedure is analogous to hashing. As we cannot guarantee uniqueness of the signatures, we have devised an efficient collision strategy. It is based on extending basic signatures to resolve aliases. This approach promises significant improvements for library matching with large libraries, for example in EPGA technology mapping.