2 research outputs found
Removing Propagation Redundant Constraints in Redundant Modeling
A widely adopted approach to solving constraint satisfaction problems
combines systematic tree search with various degrees of constraint propagation
for pruning the search space. One common technique to improve the execution
efficiency is to add redundant constraints, which are constraints logically
implied by others in the problem model. However, some redundant constraints are
propagation redundant and hence do not contribute additional propagation
information to the constraint solver. Redundant constraints arise naturally in
the process of redundant modeling where two models of the same problem are
connected and combined through channeling constraints. In this paper, we give
general theorems for proving propagation redundancy of one constraint with
respect to channeling constraints and constraints in the other model. We
illustrate, on problems from CSPlib (http://www.csplib.org/), how detecting and
removing propagation redundant constraints in redundant modeling can
significantly speed up constraint solving.Comment: 30 pages, submitted to ACM Transactions on Computational Logic (TOCL
Propagation redundancy for permutation channels
Finding a good model of a constraint satisfaction problem (CSP) is a challenging task. A modeller must specify a set of constraints that capture the definitions of the problem, and th