Test Generation 217 TABLE 4.11 ± GA Parameter Values Vector Length (L) Population Size Mutation Probability < 4 8 1/8 4–16 16 1/16 17–49 16 1 /L 50–63 24 1 /L 64–99 24 1/64 > 99 32 1/64 on fault detection. Phase two continues until no more faults can be detected, at which point GATEST enters phase three. Similar to phase two, phase three aims to detect as many faults as possible, except that the fitness function now accounts for the fault-free and faulty circuit activities in addition to fault detection and prop-agation. Individuals that induce more activity would have higher fitness values. GATEST allows for phase three to exit and return to phase two when vectors are found to detect additional faults. Finally, in phase four, sequences of vectors are used as individuals, and the fitness function is similar to phase two, except that the test sequence length is also factored in. The fitness of a candidate test for each phase is calculated as follows: ± Phase 1—Fitness is a function of total new flip-flops initialized. ± Phase 2—Fitness is a function of the number of faults detected and the number
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