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Summary: Breaking Instance-Independent Symmetries in Exact Graph Coloring
Arathi Ramani, Fadi A. Aloul, Igor L. Markov and Karem A. Sakallah
Department of EECS, University of Michigan, Ann Arbor, USA
{ramania, faloul, imarkov, karem}@umich.edu
School of Computer Engineering, American University in Dubai, UAE
Abstract
Code optimization and high level synthesis can be posed
as constraint satisfaction and optimization problems, such
as graph coloring used in register allocation. Naturally-
occurring instances of such problems are often small and
can be solved optimally. A recent wave of improvements
in algorithms for Boolean satisfiability (SAT) and 0-1 ILP
suggests generic problem-reduction methods, rather than
problem-specific heuristics, because (1) heuristics are eas-
ily upset by new constraints, (2) heuristics tend to ignore
structure, and (3) many relevant problems are provably in-
approximable. The NP-spec project offers a language to
specify NP-problems and automatic reductions to SAT.
Problem reductions often lead to highly symmetric SAT
instances, and symmetries are known to slow down SAT
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