A Filter for the Circuit Constraint

We present an incomplete filtering algorithm for the circuit constraint. The filter removes redundant values by eliminating nonhamiltonian edges from the associated graph. We identify nonhamiltonian edges by analyzing a smaller graph with labeled edges that is defined on a separator of the original graph. The complexity of the procedure for each separator S is approximately O(|S|⁵).We found that it identified all infeasible instances and eliminated about one-third of the redundant domain elements in feasible instances.