Constraint Model Enhancement by Automated Common Subexpression Elimination

The modelling bottleneck in Constraint Modelling prevents the widespread use of Constraint Programming techniques. Automated Constraint Modelling addresses this problem. To enhance automatically generated models, we eliminate common subexpressions during the modelling process, as compilers do when compiling source code. Common subexpression elimination can lead to a dramatic reduction in the size of a constraint problem, as well as a reduction in solving time and the same number of search nodes. Furthermore, it can lead to enhanced propagation and reduced search. Thus we propose common subexpression elimination as an important technique for Constraint Programming.