Local refinement method for optimizing clock tree topology

An effective method that incorporates with the Deferred-Merge Embedding algorithm is presented for clock tree construction. To achieve better performance, a sequence of tree topologies are generated by a local refinement technique. Three types of local perturbations are considered, namely swapping, tree rotation and H-flip. To speedup the proposed method, incremental cost updating is used. Experimental results show that total wirelength could be reduced effectively around 10% under Elmore delay model.