WRAPTure: a tool for evaluation and optimization of weights for weighted random pattern testing

Two problems in weighted random pattern testing are addressed: 1) finding the expected test length to sample all patterns in a given test set for a given weight set; and 2) finding the optimal weight set for minimizing expected test length for a given test set. Exact analytical expressions for expected test length for sampling all patterns from a test set are given. Expressions for approximating this quantity are also derived. Based on these results an algorithm is formulated to obtain the optimal weight assignment. Experiments carried out on test sets for several circuits (including ISCAS ´85 benchmarks) yield of the order of 95% to 100% reduction in expected test length over that achieved by current techniques