Model Restarts for Structural Symmetry Breaking

An Adaptive Model Restarts Heuristic

“…We use a geometric restart policy with the base of 100 backtracks and a growth coefficient of 1.1. This ensure that restarts are rapid as in [12]. Tables 1-2 give average times and the number of backtracks for the DOWD and IMPACT branching heuristics over 10 runs.…”

“…Our second and third case studies consider classes of problems on which model restarts has been shown to outperform other static and dynamic symmetry breaking methods [12]. We ran experiments with the "signature" based static symmetry breaking constraints proposed for variable and value interchangeability in [11] and denoted here as GCC-based.…”

“…We decomposed the GCC constraint into AMONG constraints so we can have access to the cardinality variables. Following [12] we only order partitions within the symmetry breaking constraints. We compute a score for all variables in each partition with respect to the used heuristic and sort the partitions according to these scores.…”

“…We use these three scoring heuristics within model restarts [12]. Model restarts was proposed to use a random variable ordering within symmetry breaking constraints in each restart.…”

“…In particular there is no pruning of symmetric values deeper in the search tree. An effective method to tackle this tension is model restarts [12]. This restarts search frequently with new and different symmetry breaking constraints.…”