133 lines
3.4 KiB
Python
133 lines
3.4 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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Decomposition of the circuit constraint in Google CP Solver.
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Cf Global constraint catalog:
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http://www.emn.fr/x-info/sdemasse/gccat/Ccircuit.html
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Solution of n=4:
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x: [2, 0, 3, 1]
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x: [3, 0, 1, 2]
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x: [1, 3, 0, 2]
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x: [3, 2, 0, 1]
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x: [1, 2, 3, 0]
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x: [2, 3, 1, 0]
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The 'orbit' method that is used here is based on some
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observations on permutation orbits.
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Compare with the following models:
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* MiniZinc: http://www.hakank.org/minizinc/circuit_test.mzn
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* Gecode: http://www.hakank.org/gecode/circuit_orbit.mzn
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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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import sys
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import string
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from constraint_solver import pywrapcp
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#
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# circuit(x)
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# constraints x to be an circuit
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#
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# Note: This assumes that x is has the domain 0..len(x)-1,
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# i.e. 0-based.
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#
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def circuit(solver, x):
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n = len(x)
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z = [solver.IntVar(0, n-1, 'z%i' % i) for i in range(n)]
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solver.Add(solver.AllDifferent(x, True))
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solver.Add(solver.AllDifferent(z, True))
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# put the orbit of x[0] in in z[0..n-1]
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solver.Add(z[0] == x[0])
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for i in range(1,n-1):
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# The following constraint give the error
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# "TypeError: list indices must be integers, not IntVar"
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# solver.Add(z[i] == x[z[i-1]])
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# solution: use Element instead
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solver.Add(z[i] == solver.Element(x,z[i-1]))
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#
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# Note: At least one of the following two constraint must be set.
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#
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# may not be 0 for i < n-1
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for i in range(1, n-1):
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solver.Add(z[i] != 0)
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# when i = n-1 it must be 0
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solver.Add(z[n-1] == 0)
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def main(n=5):
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# Create the solver.
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solver = pywrapcp.Solver('Send most money')
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# data
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print "n:", n
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# declare variables
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# Note: domain should be 0..n-1
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x = [solver.IntVar(0,n-1,"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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circuit(solver, x)
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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(x)
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collector = solver.AllSolutionCollector(solution)
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solver.Solve(solver.Phase(x,
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solver.CHOOSE_FIRST_UNBOUND,
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solver.ASSIGN_MIN_VALUE),
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[collector])
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num_solutions = collector.solution_count()
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for s in range(num_solutions):
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current = collector.solution(s)
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print "x:", [current.Value(x[i]) for i in range(len(x))]
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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 "wall_time:", solver.wall_time()
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print
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n = 5
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if __name__ == '__main__':
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if len(sys.argv) > 1:
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n=string.atoi(sys.argv[1])
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main(n)
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