Learning and using hyper-heuristics for variable and value ordering in constraint satisfaction problems

This paper explores the use of hyper-heuristics for variable and value ordering in binary Constraint Satisfaction Problems (CSP). Specifically, we describe the use of a symbolic cognitive architecture, augmented with constraint based reasoning as the hyper-heuristic machine learning framework. The underlying design motivation of our approach is to "do more with less." Specifically, the approach seeks to minimize the number of low level heuristics encoded yet dramatically expand the expressiveness of the hyper-heuristic by encoding the constituent measures of each heuristic, thereby providing more opportunities to achieve improved solutions. Further, the use of a symbolic cognitive architecture allows us to encode hierarchical preferences which extend the effectiveness of the hyper-heuristic across problem types. Empirical experiments are conducted to generate and test hyper-heuristics for two benchmark CSP problem types: Map Coloring; and, Job Shop Scheduling. Results suggest that the hyper-heuristic approach provides a dramatically higher level of representational granularity allowing superior intra-problem and inter-problem solutions to be secured over traditional combinations of variable and value ordering heuristics.