132 lines
4.0 KiB
Python
132 lines
4.0 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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All different except 0 Google CP Solver.
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Decomposition of global constraint alldifferent_except_0.
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From Global constraint catalogue:
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http://www.emn.fr/x-info/sdemasse/gccat/Calldifferent_except_0.html
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'''
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Enforce all variables of the collection VARIABLES to take distinct
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values, except those variables that are assigned to 0.
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Example
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(<5, 0, 1, 9, 0, 3>)
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The alldifferent_except_0 constraint holds since all the values
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(that are different from 0) 5, 1, 9 and 3 are distinct.
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'''
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Compare with the following models:
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* Comet: http://hakank.org/comet/alldifferent_except_0.co
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* ECLiPSe: http://hakank.org/eclipse/alldifferent_except_0.ecl
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* Tailor/Essence': http://hakank.org/tailor/alldifferent_except_0.eprime
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* Gecode: http://hakank.org/gecode/alldifferent_except_0.cpp
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* Gecode/R: http://hakank.org/gecode_r/all_different_except_0.rb
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* MiniZinc: http://hakank.org/minizinc/alldifferent_except_0.mzn
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* SICStus_ http://hakank.org/sicstus/alldifferent_except_0.pl
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* Choco: http://hakank.org/choco/AllDifferentExcept0_test.java
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* JaCoP: http://hakank.org/JaCoP/AllDifferentExcept0_test.java
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* Zinc: http://hakank.org/minizinc/alldifferent_except_0.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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#
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# Decomposition of alldifferent_except_0
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# Thanks to Laurent Perron (Google) for
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# suggestions of improvements.
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#
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def alldifferent_except_0(solver, a):
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n = len(a)
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for i in range(n):
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for j in range(i):
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bi = solver.IsDifferentCstVar(a[i],0)
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bj = solver.IsDifferentCstVar(a[j],0)
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bij = solver.IsDifferentVar(a[i],a[j])
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solver.Add(bi*bj <= bij)
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# more compact version:
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def alldifferent_except_0_b(solver, a):
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n = len(a)
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[solver.Add(solver.IsDifferentCstVar(a[i],0)*
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solver.IsDifferentCstVar(a[j],0) <=
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solver.IsDifferentVar(a[i],a[j]))
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for i in range(n) for j in range(i)]
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def main(unused_argv):
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# Create the solver.
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solver = pywrapcp.Solver('Alldifferent except 0')
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# data
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n = 7
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# declare variables
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x = [solver.IntVar(0,n-1, 'x%i' % i) for i in range(n)]
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z = solver.IntVar(0,n-1, 'z') # number of zeros
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#
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# constraints
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#
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alldifferent_except_0(solver, x)
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# we require 2 0's
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z_tmp = [solver.BoolVar('z_tmp % i' % i) for i in range(n)]
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for i in range(n):
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solver.Add(solver.IsEqualCstCt(x[i], 0, z_tmp[i]))
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solver.Add(solver.Sum(z_tmp) == z)
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solver.Add(z == 2)
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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[i] for i in range(n)])
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solution.Add(z)
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collector = solver.AllSolutionCollector(solution)
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solver.Solve(solver.Phase([x[i] for i in range(n)],
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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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print "x:", [collector.Value(s, x[i]) for i in range(n)]
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print "z:", collector.Value(s, z)
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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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if __name__ == '__main__':
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main("cp sample")
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