Optimization of Simple Tabular Reduction for Table Constraints

International audienceTable constraints play an important role within constraint program- ming. Recently, many schemes or algorithms have been proposed to propagate ta- ble constraints or/and to compress their representation. We show that simple tabu- lar reduction (STR), a technique proposed by J. Ullmann to dynamically maintain the tables of supports, is very often the most efficient practical approach to en- force generalized arc consistency within MAC. We also describe an optimization of STR which allows limiting the number of operations related to validity check- ing or search of supports. Interestingly enough, this optimization makes STR potentially r times faster where r is the arity of the constraint(s). The results of an extensive experimentation that we have conducted with respect to random and structured instances indicate that the optimized algorithm we propose is usually around twice as fast as the original STR and can be up to one order of magnitude faster than previous state-of-the-art algorithms on some series of instances