I. P. Gent and B. M. Smith. Symmetry breaking during search in constraint programming. In Proceedings of ECAI'00, pages 599--603, 2000.  Home/Search   Document Details and Download   Summary   Related Articles   Check

....make it challenging to solve even small instances in reasonable time: the social golfer problem is highly symmetric, and the clique structure of the constraints ensuring that any two golfers do not play together more than once makes it hard to judge the feasibility of a partial assignment. In [3, 5, 6, 10], di erent methods for the e cient handling of symmetries in the social golfer problem have been presented. In this paper we use SBDD [3] and focus on the problems caused by the constraint structure of the problem. 2 Heuristic Constraint Propagation In a tree search for the social golfers, it is ....

I.P. Gent and B.M. Smith. Symmetry Breaking During Search in Constraint Programming, Proc. of ECAI'2000, pp. 599-603, 2000.

.... solutions are related by the symmetries of three dimensional space [1] There has recently been a great deal of interest in modifying search procedures to take into account the symmetries in a problem and to stop a search procedure exploring a previously explored symmetrically equivalent paths [11, 2, 9], an early precursor of this work can be found in [3] The methods in [11, 2, 9] add constraints dynamically during search. At each node during search a constraint (depending on the current partial assignment) has to be added for each symmetry of the problem. It is easy to show that the set of ....

.... has recently been a great deal of interest in modifying search procedures to take into account the symmetries in a problem and to stop a search procedure exploring a previously explored symmetrically equivalent paths [11, 2, 9] an early precursor of this work can be found in [3] The methods in [11, 2, 9] add constraints dynamically during search. At each node during search a constraint (depending on the current partial assignment) has to be added for each symmetry of the problem. It is easy to show that the set of symmetries of a CSP form a group. One of the interesting facts of group theory is ....

[Article contains additional citation context not shown here]

Ian P. Gent and Smith Barbara. Symmetry breaking during search in constraint programming. In Proceedings of ECAI2000, pages 599-603, 2000.

....contain more than 10 symmetries. Because of its highly symmetric structure, the social golfer problem has been used as a playground for research on the systematic breaking of symmetries in recent years. In [14] Barbara Smith applied an approach that breaks symmetries during the search (SBDS [8]) to the social golfer problem. In combination with careful model selection she was able to e ciently break most of the symmetries, but still found non unique solutions for the instances studied. Note that work is in progress which removes SBDS s need for an explicit list of symmetries [9] ....

I.P. Gent and B. Smith. Symmetry Breaking During Search in Constraint Programming, Report 99.02, University of Leeds, Jan. 1999.

.... naturally exhibit symmetries and symmetry breaking may drastically improve performance (e.g. Barnier and Brisset, 2002; Meseguer and Torras, 2001; Puget, 2002] An important contribution in this area has been the development of various general schemes for symmetry breaking in CSPs (e.g. SBDS [Gent and Smith, 2000] and SBDD [Fahle et al. 2001; Focacci and Milano, 2001] Unfortunately, these schemes, in general, may require exponential resources to break all symmetries. Indeed, some schemes require exponential space to store all the nogoods generated through symmetries, while others may take exponential ....

Ian P. Gent and B. Smith. Symmetry breaking during search in constraint programming. In ECAI'2000.

....improves performance signi cantly: a systematic search for sequences of length 44 took approximately 2 days, as opposed to an extrapolated 68 days for exhaustive enumeration. Symmetry breaking exploits the fact that sequences occur in equivalence classes of size 8. Gent Smith [10] have also successfully applied generic symmetry breaking techniques to LABS. However, even with these enhancements, systematic search is unlikely to scale up to large sequences. LABS provides little scope for constraint propagation, and it is conjectured [23] that for N 100 progress will be ....

I. Gent, B. Smith. Symmetry Breaking During Search in Constraint Programming. Research Report 99.02, Department of Computer Science, University of Leeds, 1999.

.... [18] The other approach is to detect and exploit symmetries dynamically during search: an ordering can be de ned on solutions, and the search restricted to the rst solutions under this ordering within each equivalence class [2] constraints may be posted at each branch point in the search tree [1, 7]; and search may be guided towards subspaces with many non symmetric states [14] Implied constraints have been shown to speed up the search for the rst solution [3, 11] but it is not clear that this will always be the case, even ignoring overheads introduced by the extra constraints. Symmetry ....

....constraints are usually applied when exhaustive search is to be performed. Here the bene ts are clear, though again the extra overheads sometimes outweigh the bene ts. However, it is known that their e ect on rst solution search are not necessarily bene cial. For example it is remarked in [7] that the more easily found solutions may inadvertently be eliminated, and in [9] that symmetry breaking does not always improve performance in the Oz system. This issue seems worth investigating further, and there are several obvious questions. Are symmetry breaking and implied constraints ....

I. P. Gent, B. Smith. Symmetry Breaking During Search in Constraint Programming. Proceedings of the Fourteenth European Conference on Arti cial Intelligence, 2000, pp. 599-603.

No context found.

I. P. Gent and B. M. Smith. Symmetry Breaking During Search in Constraint Programming. In W. Horn, editor, Proceedings ECAI'

No context found.

I. P. Gent and B. M. Smith, `Symmetry Breaking During Search in Constraint Programming', in Proc. ECAI'2000.

No context found.

I. P. Gent and B. M. Smith. Symmetry Breaking During Search in Constraint Programming. In W. Horn, editor, Proceedings ECAI'2000, pages 599--603, 2000.

No context found.

I. P. Gent and B. M. Smith. Symmetry Breaking During Search in Constraint Programming. In W. Horn, editor, Proceedings ECAI'2000, pages 599--603, 2000.

No context found.

I. P. Gent and B. M. Smith. Symmetry Breaking During Search in Constraint Programming. In W. Horn, editor, Proceedings ECAI'2000.

....used to break symmetry. As a higher level model is re ned into a CSP instance, the preconditions are tested and symmetry is broken among the objects that are symmetrical in this instance. For example, the symmetry among the rings can be eliminated using Symmetry Breaking During Search (SBDS) [8]. SBDS takes in a description of the action of each symmetry on decisions made during search (i.e. to assign or not to assign a value to a variable) Once a decision has been explored, if the search backtracks to explore its alternative, SBDS ensures that further decisions symmetric to those ....

I. P. Gent and B. M. Smith. Symmetry Breaking During Search in Constraint Programming. Proc. European Conference on AI, pages 599-603, 2000.

No context found.

I. P. Gent and B. M. Smith. Symmetry breaking during search in constraint programming. In Proceedings of ECAI'00, pages 599--603, 2000.

No context found.

I.P. Gent and B. Smith. Symmetry Breaking During Search in Constraint Programming, Report 99.02, University of Leeds, Jan. 1999.

No context found.

I.P. Gent and B. Smith. Symmetry Breaking During Search in Constraint Programming, Report 99.02, University of Leeds, Jan. 1999.

No context found.

I.P. Gent and B. Smith. Symmetry breaking during search in constraint programming. In ECAI, 2000.

No context found.

I. Gent and B. Smith. Symmetry breaking during search in constraint programming. In Proceedings of ECAI-2000, pages 599-603, 2000.

No context found.

I Gent and B Smith. Symmetry breaking during search in constraint programming. In Proceedings of ECAI'2000, pages 599-603, 2000.

No context found.

I. P. Gent and B. M. Smith. Symmetry breaking during search in constraint programming. In Proceedings of the 14th European Conference on Artificial Intelligence, pages 599--603, 2000.

No context found.

I.P. Gent and B.M. Smith. Symmetry breaking during search in constraint programming. In Proceedings of ECAI'00, pages 599--603, 2000.

No context found.

I.P. Gent, B.M. Smith. Symmetry breaking during search in constraint programming. In Proceedings of the 14th European Conference on Artificial Intelligence, pp 599--603, 2000.

No context found.

I. P. Gent and B. Smith. Symmetry breaking during search in constraint programming. In Proc. of ECAI 2000, pages 599--603, 2000.

No context found.

B. M. Smith and I. P. Gent, \Symmetry Breaking During Search in Constraint Programming, " Proc. of the European Conference on Arti cial Intelligence, Berlin, Germany, Aug. 2000, pp. 599-603.

No context found.

I.P. Gent and B. Smith. Symmetry Breaking During Search in Constraint Programming. Proc. of ECAI'2000, Berlin, pp. 599603, 2000.

No context found.

I. P. Gent and B. M. Smith. Symmetry breaking during search in constraint programming. In W. Horn, editor, Proceedings ECAI 2000.

First 50 documents

Online articles have much greater impact   More about CiteSeer.IST   Add search form to your site   Submit documents   Feedback  

CiteSeer.IST - Copyright Penn State and NEC