1. A method of locating systematic defects in integrated circuits, said method comprising: performing preliminary extracting and index processing of a circuit design comprising: transforming shapes in a circuit layout into feature vectors; and comparing said feature vectors to produce an index of feature vectors; and after performing said preliminary extracting and index processing, performing a process of feature searching comprising: identifying a defect region of said circuit layout; transforming shapes in said defect region into defect vectors; and finding feature vectors that are similar to said defect vectors using said index of feature vectors.