Enhancement schemes for constraint processing: backjumping, learning, and cutset decomposition
Artificial Intelligence
Local optima topology for the k-coloring problem
Discrete Applied Mathematics - Special volume: viewpoints on optimization
The hardest constraint problems: a double phase transition
Artificial Intelligence
Exploiting the deep structure of constraint problems
Artificial Intelligence
New methods to color the vertices of a graph
Communications of the ACM
Improved algorithms for 3-coloring, 3-edge-coloring, and constraint satisfaction
SODA '01 Proceedings of the twelfth annual ACM-SIAM symposium on Discrete algorithms
Frozen development in graph coloring
Theoretical Computer Science - Phase transitions in combinatorial problems
On the Hardness of 4-Coloring a 3-Colorable Graph
COCO '00 Proceedings of the 15th Annual IEEE Conference on Computational Complexity
Systematic Generation of Very Hard Cases for Graph 3-Colorability
TAI '95 Proceedings of the Seventh International Conference on Tools with Artificial Intelligence
A new look at the easy-hard-easy pattern of combinatorial search difficulty
Journal of Artificial Intelligence Research
Sparse constraint graphs and exceptionally hard problems
IJCAI'95 Proceedings of the 14th international joint conference on Artificial intelligence - Volume 1
Analysis of phase transitions in graph-coloring problems based on constraint structures
PRICAI'00 Proceedings of the 6th Pacific Rim international conference on Artificial intelligence
The very particular structure of the very hard instances
AAAI'96 Proceedings of the thirteenth national conference on Artificial intelligence - Volume 1
IEA/AIE'10 Proceedings of the 23rd international conference on Industrial engineering and other applications of applied intelligent systems - Volume Part III
Computing infeasibility certificates for combinatorial problems through Hilbert's Nullstellensatz
Journal of Symbolic Computation
Further results on swarms solving graph coloring
ICCSA'10 Proceedings of the 2010 international conference on Computational Science and Its Applications - Volume Part III
An empirical comparison of some approximate methods for graph coloring
HAIS'12 Proceedings of the 7th international conference on Hybrid Artificial Intelligent Systems - Volume Part I
The Cunningham-Geelen Method in Practice: Branch-Decompositions and Integer Programming
INFORMS Journal on Computing
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Graph colorability (COL), is a typical constraint satisfaction problem to which phase transition phenomena (PTs), are important in the computational complexity of combinatorial search algorithms. PTs are significant and subtle because, in the PT region, extraordinarily hard problem instances are found, which may require exponential-order computational time to solve. To clarify PT mechanism, many studies have been undertaken to produce very hard instances, many of which were based on generate-and-test approaches. We propose a rather systematic or constructive algorithm that repeats the embedding of 4-critical graphs to arbitrarily generate large extraordinarily hard 3-colorability instances. We demonstrated experimentally that the computational cost to solve our generated instances is of an exponential order of the number of vertices by using a few actual coloring algorithms and constraint satisfaction algorithms.