Pattern matching and refinement hybrid approach to circuit comparison

We present a new approach to circuit comparison which was developed to combine general applicability with most of the advantages of hierarchical processing. Two reasons often prevent hierarchical cell by cell comparison: hierarchical circuit extraction cannot be performed in all cases and if so, the resulting hierarchy is often non-isomorphic to the schematic hierarchy. Therefore, general applicability requires the ability to cope with flat circuits. Consequently, many tools compare flat netlists of transistors or logic gates. On the other hand, apart from the speed-up, hierarchical processing is superior in terms of error localization and functional but not topological isomorphism. Our objective was to develop a tool which exploits the latter two advantages of hierarchical processing, while not sacrificing general applicability. The basic principle of operation is the pattern matching of arbitrary subcircuits in larger circuits.