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A Column Generation Approach For Graph Coloring
 INFORMS Journal on Computing
, 1995
"... We present a method for solving the independent set formulation of the graph coloring problem (where there is one variable for each independent set in the graph). We use a column generation method for implicit optimization of the linear program at each node of the branchandbound tree. This approac ..."
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Cited by 89 (2 self)
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We present a method for solving the independent set formulation of the graph coloring problem (where there is one variable for each independent set in the graph). We use a column generation method for implicit optimization of the linear program at each node of the branchandbound tree. This approach, while requiring the solution of a difficult subproblem as well as needing sophisticated branching rules, solves small to moderate size problems quickly. We have also implemented an exact graph coloring algorithm based on DSATUR for comparison. Implementation details and computational experience are presented. 1 INTRODUCTION The graph coloring problem is one of the most useful models in graph theory. This problem has been used to solve problems in school timetabling [10], computer register allocation [7, 8], electronic bandwidth allocation [11], and many other areas. These applications suggest that effective algorithms for solving the graph coloring problem would be of great importance. D...
Breaking instanceindependent symmetries in exact graph coloring
 JOURNAL OF ARTIFICIAL INTELLIGENCE RESEARCH
, 2004
"... Code optimization and high level synthesis can be posed as constraint satisfaction and optimization problems, such as graph coloring used in register allocation. Naturallyoccurring instances of such problems are often small and can be solved optimally. A recent wave of improvements in algorithms for ..."
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Cited by 17 (5 self)
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Code optimization and high level synthesis can be posed as constraint satisfaction and optimization problems, such as graph coloring used in register allocation. Naturallyoccurring instances of such problems are often small and can be solved optimally. A recent wave of improvements in algorithms for Boolean satisfiability (SAT) and 01 ILP suggests generic problemreduction methods, rather than problemspecific heuristics, because (1) heuristics are easily upset by new constraints, (2) heuristics tend to ignore structure, and (3) many relevant problems are provably inapproximable. The NPspec project offers a language to specify NPproblems and automatic reductions to SAT. Problem reductions often lead to highly symmetric SAT instances, and symmetries are known to slow down SAT solvers. In this work, we compare several avenues for symmetrybreaking, in particular when certain kinds of symmetry are present in all generated instances. Our surprising conclusion is that instanceindependent symmetries should often be processed together with instancespecific symmetries rather than earlier, at the specification level.