METHOD AND APPARATUS FOR APPROXIMATING DIAGONAL LINES IN PLACEMENT

Some embodiments of the invention provide a method for placing circuit modules in an integrated circuit (“IC”) layout. The method computes a placement metric for the IC layout. In some embodiments, computing the placement metric includes partitioning a region of the IC layout into several sub-regions by using a cut graph, where the cut graph is an approximation of a diagonal cut line. These embodiments then generate congestion-cost estimates by measuring the number of nets cut by the cut graph. In some embodiments, the cut graph is a staircase cut graph. These staircase cut graphs include several horizontal and vertical cut lines. In some embodiments, the cut graph is a cut arc.