net clustering based macrocell placement
Given an RTL (Register-Transfer-Level) netlist, a net dependency graph with weighted edges is built. Each node in the graph represents a net and an edge exists between two nodes if the two nets represented by the nodes share one or more macrocells. Clusters of nets are then formed by clique partitioning. A net cluster level floorplan is derived by simulated annealing to define the regions where the nets in each cluster must be routed. The macrocell placement is formulated as a force-directed problem where the terminals of a net are free to move under the influence of forces in the quest for optimal length of the net. A new type of rejection force is introduced in order to obtain a feasible placement. In comparison with the placements generated by CADENCE Silicon Ensemble, we obtained an average total wire length reduction of 22.8\% and an average longest wire length reduction of 33\% with an average area penalty of only 1.1\%.
net clustering macrocell placement force-directed placement net placement net prioritization iterative improvement