8927b03942
Some of these imports are not used. The rest of them only import string to use the string.atoi function. But string.atoi(s) on a string input is identical to just int(s). See the docs: "deprecated since 2.0".
135 lines
3.2 KiB
Python
135 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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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:
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http://www.hakank.org/google_or_tools/
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"""
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from __future__ import print_function
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import sys
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from ortools.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))
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solver.Add(solver.AllDifferent(z))
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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.SolutionCount()
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for s in range(num_solutions):
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print("x:", [collector.Value(s, 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("WallTime:", solver.WallTime())
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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 = int(sys.argv[1])
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main(n)
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