NACRE - A Nogood And Clause Reasoning Engine

Abstract

NACRE, for Nogood And Clause Reasoning Engine, is a constraint solver written in C++. It is based on a modular architecture designed to work with generic constraints while implementing several state-of-the-art search methods and heuristics. Interestingly, its data structures have been carefully designed to play around nogoods and clauses, making it suit- able for implementing learning strategies. NACRE was submitted to the CSP MiniTrack of the 2018 and 2019 XCSP3 [8] competitions where it took the first place. This paper gives a general description of NACRE as a framework. We present its kernel, the available search algorithms, and the default settings (notably, used for XCSP3 competitions), which makes NACRE efficient in practice when used as a black-box solver.

Compositional workflow modeling with priority constraints

“…We defined data flow in a Reo network in the form of mathematical expressions on data observed at various nodes or ports. The main advantage of such representation is the possibility to use existing highly optimized constraint solvers [25,26] to infer the behavior of a network given the semantics of its constituent parts.…”