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We present new techniques for improving search in a hybrid Davis-Putnam-Logemann-Loveland based constraint solver for RTL (register-transfer level) circuits (HDPLL). In earlier work on HDPLL (Parthasarathy, G. et al., 41st DAC, 2004), the authors combined solvers for integer and Boolean domains using finite-domain constraint propagation with heuristic conflict-based learning. We describe a new algorithm that extends the conflict-based unique-implication point learning in Boolean SAT (satisfiability) solvers to hybrid Boolean-integer domains in HDPLL. We describe data-structures for efficient constraint propagation on the hybrid learned relations, similar to two-literal watching in Boolean SAT. We demonstrate that these new techniques provide considerable performance benefits when compared with other combinations of decision theories.
Design, Automation and Test in Europe, 2005. Proceedings
Date of Conference: 7-11 March 2005