1. An electro-optical inspection method comprising: a. imaging at least a portion of a semiconductor wafer; i. wherein the wafer includes at least two regions, including a first region comprising a plurality of memory cells of a first type and a second region comprising a plurality of memory cells of a second type; ii. wherein at least one type of cells has a repetition vector different from at least one other type of cells; b. accessing data that defines at least one repetition vector for each type of cells; and c. inspecting each region using a cell-to-cell comparison method based on data including the at least one repetition vector for the type of cells in each respective region.