An efficient heuristic force directed placement algorithm based on partitioning

摘要

An efficient heuristic force directed placement algorithm based on partitioning is proposed for very large-scale circuits. Our heuristic force directed approach provides a more efficient cell location adjustment scheme for iterative placement optimization than the force directed relaxation (FDR) method. We apply hierarchical partitioning based on a new parallel clustering technique to decompose circuit into several level sub-circuits. During the partitioning phase, a similar technique to 'terminal propagation' was introduced so as to maintain the external connections that affect cell adjustment in sub-circuit. In these lowest level sub-circuits, the heuristic force directed algorithm is used to perform iterative placement optimization. Then each pair of sub-circuits resulted from bisection combine into a larger one, in which cells are located as the best placement state of either sub-circuits. The bottom-up combination is done successively until back to the original circuit, and at each combination level the heuristic force directed placement algorithm is used to further improve the placement quality. A set of MCNC ( Microelectronics Centre of North-Carolina) standard cell benchmarks is experimented and results show that our placement algorithm produces on average of 12% lower total wire length than that of Feng Shui with a little longer CPU time.