We give the first examples of non-trivially positively-useless predicates subject only to P 6= NP. In particular, for every constraint function Q : {−1, 1}4 → R, we construct Contraint-SatisfactionProblem (CSP) instances without negations which have value at least 1 − ε when evaluted for the arity-four odd-parity predicate, yet it is NP-hard to find a solution with value significantly better th...

1 Intro In my 1988 SIGPLAN paper “Control-Flow Analysis in Scheme,” I promised to cover several items in more detail in a “forthcoming tech report.” The tech report has yet to happen. Most of the promised items have been covered in other papers (“The Semantics of Scheme Control-Flow Analysis” and “Data-Flow Analysis and Type Recovery in Scheme”). Useless-variable elimination, however, is still ...

Planning as heuristic search is a powerful approach to solving domain independent planning problems. In recent years, various successful heuristics and planners like FF, LPG, FAST DOWNWARD or SGPLAN have been proposed in this context. However, as heuristics only estimate the distance to goal states, a general problem of heuristic search is the existence of plateaus in the search space topology ...

The critical pair/completion (CPC) technique was initiated in the mid sixties in three separated areas: theorem proving [12], polynomial ideal theory [3] and term rewriting [9]. For theoretical and practical reasons, improvements of CPC algorithms were developed in two main directions. The rst one concerns strategies for selecting critical pairs. In [10], strategies consisting in adding the new...