# Copyright 2010 Hakan Kjellerstrand hakank@bonetmail.com
#
# Licensed under the Apache License, Version 2.0 (the 'License');
# you may not use this file except in compliance with the License.
# You may obtain a copy of the License at
#
# http://www.apache.org/licenses/LICENSE-2.0
#
# Unless required by applicable law or agreed to in writing, software
# distributed under the License is distributed on an 'AS IS' BASIS,
# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
# See the License for the specific language governing permissions and
# limitations under the License.
"""
Scheduling speakers problem in Google CP Solver.
From Rina Dechter, Constraint Processing, page 72
Scheduling of 6 speakers in 6 slots.
Compare with the following models:
* MiniZinc: http://www.hakank.org/minizinc/scheduling_speakers.mzn
* SICStus Prolog: http://www.hakank.org/sicstus/scheduling_speakers.pl
* ECLiPSe: http://hakank.org/eclipse/scheduling_speakers.ecl
* Gecode: http://hakank.org/gecode/scheduling_speakers.cpp
This model was created by Hakan Kjellerstrand (hakank@bonetmail.com)
Also see my other Google CP Solver models:
http://www.hakank.org/google_or_tools/
"""
from ortools.constraint_solver import pywrapcp
def main():
# Create the solver.
solver = pywrapcp.Solver('Scheduling speakers')
#
# data
#
n = 6 # number of speakers
# slots available to speak
available = [
# Reasoning:
[3, 4, 5, 6], # 2) the only one with 6 after speaker F -> 1
[3, 4], # 5) 3 or 4
[2, 3, 4, 5], # 3) only with 5 after F -> 1 and A -> 6
[2, 3, 4], # 4) only with 2 after C -> 5 and F -> 1
[3, 4], # 5) 3 or 4
[1, 2, 3, 4, 5, 6] # 1) the only with 1
]
#
# variables
#
x = [solver.IntVar(1, n, 'x[%i]' % i) for i in range(n)]
#
# constraints
#
solver.Add(solver.AllDifferent(x))
for i in range(n):
solver.Add(solver.MemberCt(x[i], available[i]))
#
# search and result
#
db = solver.Phase(x,
solver.INT_VAR_DEFAULT,
solver.INT_VALUE_DEFAULT)
solver.NewSearch(db)
num_solutions = 0
while solver.NextSolution():
num_solutions += 1
print 'x:', [x[i].Value() for i in range(n)]
solver.EndSearch()
print
print 'num_solutions:', num_solutions
print 'failures:', solver.Failures()
print 'branches:', solver.Branches()
print 'WallTime:', solver.WallTime(), 'ms'
if __name__ == '__main__':
main()