A common type of symmetry is when both variables and values partition into
interchangeable sets. Polynomial methods have been introduced to eliminate all symmetric
solutions introduced by such interchangeability. Unfortunately, whilst eliminating all
symmetric solutions is tractable in this case, pruning all symmetric values is NP-hard. We
introduce a new global constraint called SigLex and its GAC propagator for pruning some
(but not necessarily all) symmetric values. We also investigate how different postings of the …

A common type of symmetry is when both variables and values partition into
interchangeable sets. Polynomial methods have been introduced to eliminate all symmetric
solutions introduced by such interchangeability. Unfortunately, whilst eliminating all
symmetric solutions is tractable in this case, pruning all symmetric values is NP-hard. We
introduce a new propagator for pruning some (but not necessarily all) symmetric values. We
show that such static symmetry breaking can be exponentially faster than dynamic methods …