Clustering algorithms have been used to improve the speed and quality of placement. Traditionally, clustering focuses on the local\r\nconnections between cells. In this paper, a new clustering algorithm that is based on the estimated lengths of circuit interconnects\r\nand the connectivity is proposed. In the proposed algorithm, first an a priori length estimation technique is used to estimate the\r\nlengths of nets. Then, the estimated lengths are used in a clustering framework to modify a clustering technique based on algebraic\r\nmultigrid (AMG), that finds the cells with the highest connectivity. Finally, based on the results from the AMG-based process,\r\nclusters are made. In addition, a new physical unclustering technique is proposed. The results show a significant improvement,\r\nreductions of up to 40%, in wire length can be achieved when using the proposed technique with three academic placers on\r\nindustry-based circuits. Moreover, the runtime is not significantly degraded and can even be improved.
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