97 lines
2.4 KiB
Python
97 lines
2.4 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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Knapsack problem in Google CP Solver.
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Simple knapsack problem.
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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 knapsack(solver, values, weights, n):
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z = solver.IntVar(0, 10000)
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x = [solver.IntVar(0,1,"x(%i)"%i) for i in range(len(values))]
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solver.Add(z >= 0)
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solver.Add(z == solver.ScalProd(x, values))
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solver.Add(solver.ScalProd(x, weights) <= n)
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return [x, z]
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def main(values, weights, n):
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# Create the solver.
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solver = pywrapcp.Solver('n-queens')
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#
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# data
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#
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print "values:", values
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print "weights:", weights
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print "n:", n
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print
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# declare variables
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#
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# constraints
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#
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[x, z] = knapsack(solver, values, weights, n)
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# objective
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objective = solver.Maximize(z,1)
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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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solution.Add(z)
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# db: DecisionBuilder
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db = solver.Phase(x,
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solver.CHOOSE_FIRST_UNBOUND,
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solver.ASSIGN_MAX_VALUE)
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solver.NewSearch(db,[objective])
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num_solutions = 0
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while solver.NextSolution():
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print "x:", [x[i].Value() for i in range(len(values))]
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print "z:", z.Value()
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print
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num_solutions += 1
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solver.EndSearch()
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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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values = [15, 100, 90, 60, 40, 15, 10, 1, 12, 12, 100]
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weights = [ 2, 20, 20, 30, 40, 30, 60, 10, 21, 12, 2]
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n = 102
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if __name__ == '__main__':
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main( values, weights, n)
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