124 lines
3.3 KiB
Python
124 lines
3.3 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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Mr Smith in Google CP Solver.
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From an IF Prolog example (http://www.ifcomputer.de/)
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'''
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The Smith family and their three children want to pay a visit but they
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do not all have the time to do so. Following are few hints who will go
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and who will not:
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o If Mr Smith comes, his wife will come too.
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o At least one of their two sons Matt and John will come.
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o Either Mrs Smith or Tim will come, but not both.
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o Either Tim and John will come, or neither will come.
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o If Matt comes, then John and his father will
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also come.
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'''
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The answer should be:
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Mr_Smith_comes = 0
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Mrs_Smith_comes = 0
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Matt_comes = 0
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John_comes = 1
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Tim_comes = 1
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Compare with the following models:
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* ECLiPSe: http://www.hakank.org/eclipse/mr_smith.ecl
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* SICStus Prolog: http://www.hakank.org/sicstus/mr_smith.pl
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* Gecode: http://www.hakank.org/gecode/mr_smith.cpp
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* MiniZinc: http://www.hakank.org/minizinc/mr_smith.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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def main():
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# Create the solver.
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solver = pywrapcp.Solver('Mr Smith problem')
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#
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# data
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#
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n = 5
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#
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# declare variables
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#
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x = [solver.IntVar(0, 1, 'x[%i]' % i) for i in range(n)]
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Mr_Smith, Mrs_Smith, Matt, John, Tim = x
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#
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# constraints
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#
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#
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# I've kept the MiniZinc constraints for clarity
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# and debugging.
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#
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# If Mr Smith comes then his wife will come too.
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# (Mr_Smith -> Mrs_Smith)
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solver.Add(Mr_Smith - Mrs_Smith <= 0)
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# At least one of their two sons Matt and John will come.
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# (Matt \/ John)
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solver.Add(Matt + John >= 1)
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# Either Mrs Smith or Tim will come but not both.
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# bool2int(Mrs_Smith) + bool2int(Tim) = 1 /\
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# (Mrs_Smith xor Tim)
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solver.Add(Mrs_Smith + Tim == 1)
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# Either Tim and John will come or neither will come.
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# (Tim = John)
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solver.Add(Tim == John)
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# If Matt comes /\ then John and his father will also come.
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# (Matt -> (John /\ Mr_Smith))
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solver.Add(Matt - (John * Mr_Smith) <= 0)
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#
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# solution and search
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#
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db = solver.Phase(x,
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solver.INT_VAR_DEFAULT,
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solver.INT_VALUE_DEFAULT)
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solver.NewSearch(db)
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num_solutions = 0
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while solver.NextSolution():
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num_solutions += 1
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print('x:', [x[i].Value() for i in range(n)])
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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(), 'ms')
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if __name__ == '__main__':
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main()
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