Improving a nonenumerative method to estimate path delay fault coverage

A recently proposed method obtains path delay fault coverages by estimating the count of the number of tested faults instead of actually enumerating them. The estimate become pessimistic when several paths share a set of lines. In this communication, we present a continuum of improved approximations for the counting method, approaching exact fault simulation, to allow trade-o s between accuracy and complexity. Higher accuracy is obtained at the expense of CPU time. We propose the use of ags corresponding to xed-length path-segments. A ag indicates whether or not the segment has been included in a previously detected path fault. A path fault, detected by a pair of vectors, is counted as a new detection only if it includes at least one segment not included in any previously tested path fault. The results show that as the length of segments is increased, the accuracy approaches close to that of the exact fault simulation even with small segment lengths.