Many parallel test pattern generation techniques have been proposed to speed up the test pattern generation (TPG) process. Focusing on acceleration, most of these techniques sacrifice determinism and often incur test set inflation. In this paper, a parallel TPG that exploits search space parallelism to improve fault coverage, called deterministic search-space parallel ATPG (DSSP-ATPG), is proposed. Static search space partitioning and dynamic search space allocation techniques are developed to coordinate the cooperating threads so as to reduce the thread idle time and ensure determinism. Experimental results on larger benchmark circuits and an industry circuit show that DSSP-TPG improves fault coverage as the thread count is increased. Furthermore, to speed up the TPG process, a hybrid ATPG scheme that integrates the DSSP-ATPG with a deterministic fault-parallel ATPG is implemented. By adjusting the extent of fault and search-space parallelism, the user can tune the hybrid ATPG towards higher fault coverage or more CPU time reduction.
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