109 lines
3.2 KiB
Python
109 lines
3.2 KiB
Python
# Copyright 2010 Hakan Kjellerstrand hakank@bonetmail.com
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#
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# Licensed under the Apache License, Version 2.0 (the "License");
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# you may not use this file except in compliance with the License.
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# You may obtain a copy of the License at
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#
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# http://www.apache.org/licenses/LICENSE-2.0
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#
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# Unless required by applicable law or agreed to in writing, software
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# distributed under the License is distributed on an "AS IS" BASIS,
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# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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# See the License for the specific language governing permissions and
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# limitations under the License.
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"""
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Map coloring problem in Google CP Solver.
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From Pascal Van Hentenryck 'The OPL Optimization Programming Language',
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page 7, 42.
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Compare with the following models:
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* Comet: http://www.hakank.org/comet/map.co
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* Tailor/Essence': http://hakank.org/tailor/map_coloring.eprime
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* SICStus: http://hakank.org/sicstus/map_coloring.pl
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* ECLiPSe: http://hakank.org/eclipse/map.ecl
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* Gecode: http://hakank.org/gecode/map.cpp
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* MiniZinc: http://hakank.org/minizinc/map.mzn
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* Zinc: http://hakank.org/minizinc/map.zinc
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This model was created by Hakan Kjellerstrand (hakank@bonetmail.com)
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Also see my other Google CP Solver models: http://www.hakank.org/google_or_tools/
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"""
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from constraint_solver import pywrapcp
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def main():
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# Create the solver.
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solver = pywrapcp.Solver('Map coloring')
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#
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# data
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#
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Belgium = 0
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Denmark = 1
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France = 2
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Germany = 3
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Netherlands = 4
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Luxembourg = 5
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n = 6
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max_num_colors = 4
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# declare variables
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color = [solver.IntVar(1,max_num_colors, 'x%i' % i) for i in range(n)]
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#
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# constraints
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#
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solver.Add(color[Belgium] == 1) # Symmetry breaking
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solver.Add(color[France] != color[Belgium])
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solver.Add(color[France] != color[Luxembourg])
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solver.Add(color[France] != color[Germany])
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solver.Add(color[Luxembourg] != color[Germany])
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solver.Add(color[Luxembourg] != color[Belgium])
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solver.Add(color[Belgium] != color[Netherlands])
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solver.Add(color[Belgium] != color[Germany])
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solver.Add(color[Germany] != color[Netherlands])
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solver.Add(color[Germany] != color[Denmark])
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#
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# solution and search
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#
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solution = solver.Assignment()
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solution.Add([color[i] for i in range(n)])
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collector = solver.AllSolutionCollector(solution)
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# collector = solver.FirstSolutionCollector(solution)
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# search_log = solver.SearchLog(100, x[0])
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solver.Solve(solver.Phase([color[i] for i in range(n)],
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solver.INT_VAR_SIMPLE,
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solver.ASSIGN_MIN_VALUE),
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[collector])
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num_solutions = collector.SolutionCount()
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print "num_solutions: ", num_solutions
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if num_solutions > 0:
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for s in range(num_solutions):
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colorval = [collector.Value(s, color[i]) for i in range(n)]
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print "color:", colorval
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print
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print "num_solutions:", num_solutions
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print "failures:", solver.Failures()
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print "branches:", solver.Branches()
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print "WallTime:", solver.WallTime()
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else:
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print "No solutions found"
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if __name__ == '__main__':
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main()
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