Electronic Design Automation

11.7. Detailed Placement

Given a legalized placement solution, detailed placement further improves the wirelength (or other objectives) by locally rearranging the standard cells while maintaining legality. There may be significant room for wirelength improvement in a legalized global placement solution for several reasons. First, global placement typically uses inaccurate wirelength models (e.g., cut cost, quadratic wire-length with clique net model, log-sum-exponential function). Second, global placement algorithms often place each cell into a subregion without paying much attention to the location of the cell within the subregion. Third, during legalization, the wirelength is likely to be worsened by the perturbations.

Simulated annealing ...