We present a novel preprocessing technique to automatically reduce the size of Boolean formulas. This technique, called Bounded Variable Addition (BVA), exchanges clauses for variables. Similar to other preprocessing techniques, BVA greedily lowers the sum of variables and clauses, a rough measure for the hardness to solve a formula. We show that cardinality constraints (CCs) can efficiently be reencoded: from a naive CC encoding, BVA automatically generates a compact encoding, which is smaller than sophisticated encodings. Experimental results show that applying BVA can improve SAT solving performance.
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