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