aspect of the technology are a method of designing a circuit layout and corresponding computer systems and nontransitory computer media . the circuit layout is for use in forming a lithographic mask set for use in fabricating an integrated circuit . in the method the computer system divides a synthesized circuit design into cell partitions along critical paths of the synthesized circuit design . the computer system associates pins of the plurality of cell partitions with normalized pin timing values . the normalized pin timing values store magnitude differences between a reference timing slack and timing slacks of the plurality of pins . after optimizing the synthesized circuit design , the computer system repeats the method , and then the computer system determines whether to further optimize the plurality of cell partitions by comparing : the pre - optimization normalized pin timing values of the plurality of cell partitions with the post - optimization normalized pin timing values of the plurality of cell partitions .