Described herein is a method for obtaining a preferred layout for a lithographic process, the method comprising: identifying an initial layout including a plurality of features; and reconfiguring the features until a termination condition is satisfied, thereby obtaining the preferred layout; wherein the reconfiguring comprises evaluating a cost function that measures how a lithographic metric is affected by a set of changes to the features for a plurality of lithographic process conditions, and expanding the cost function into a series of terms at least some of which are functions of characteristics of the features.