Correcting a mask pattern includes accessing the mask pattern segmented into segments. An attribute value is established for each segment, where the attribute value for a segment describes an attribute of the segment. The following is repeated for one or more of the attribute values to generate a corrected mask pattern: selecting segments using one or more attribute values; calculating a current correction value for each of the selected segments with respect to previously selected segments updated according to previously calculated correction values; and updating the selected segments according to the current correction values.