Snake Lex: An Alternative to Double Lex
نویسندگان
چکیده
Complete row and column symmetry breaking in constraint models using the lex leader method is generally prohibitively costly. Double lex, which is derived from lex leader, is commonly used in practice as an incomplete symmetrybreaking method for row and column symmetries. Double lex is based on a rowwise canonical variable ordering. However, this choice is arbitrary. We investigate other canonical orderings and focus on one in particular: snake ordering. From this we derive a corresponding incomplete set of symmetry breaking constraints, snake lex. Experimental data comparing double lex and snake lex shows that snake lex is substantially better than double lex in many cases.
منابع مشابه
In Search of a Better Method to Break Row and Column Symmetries
Complete row and column symmetry breaking in constraint satisfaction problems using the lex leader method is generally prohibitively costly. Double lex, which is derived from lex leader, is commonly used in practice as an incomplete symmetry-breaking method for row and column symmetries. This technique uses a row-wise ordering to construct the lex leader. For this reason, it is generally counte...
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