1. A method of determining a location of one or more features within a mask layout of a device manufacturing process involving — lithography, the method comprising: performing, by a hardware computer, a simulation involving the mask layout based on a placement of a first feature in the mask layout, wherein performing the simulation includes generating a SRAF guidance map that is a two-dimensional set of values respectively corresponding to points in the mask layout; and determining a location for placing a second feature in the mask layout based on the two-dimensional set of values respectively corresponding to points in the mask layout, wherein the determined location comprises one or more of the points.