Comparative Study by Solving the Test Compaction Problem

Beside issues like the low power dissipation and the increase of defect coverage, test compaction is an important requirement regarding large scale integration (LSI) testing. The overall cost of a VLSI circuit's testing depends on the length of its test sequence; therefore the reduction of this sequence, keeping the coverage, will lead to a reduction of used resources in the testing process. In this paper we study test vectors over a five-valued logic. The problem of finding minimal test sets is NP-complete. Consequently, an optimal algorithm has limited practical use and is only applicable to small problem instances. We describe three approaches for reducing the length of test sequences: an optimal algorithm using a recursive backtracking method (OPT) and two greedy algorithms (GRNV and GRBT). The behavior of these algorithms is discussed and analyzed by experiments. Finally, directions for future work are given.