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# Copyright 2010 Hakan Kjellerstrand hakank@gmail.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.
"""

  Organizing a day in Google CP Solver.

  Simple scheduling problem.

  Problem formulation from ECLiPSe:
  Slides on (Finite Domain) Constraint Logic Programming, page 38f
  http://eclipse-clp.org/reports/eclipse.ppt


  Compare with the following models:
  * MiniZinc: http://www.hakank.org/minizinc/organize_day.mzn
  * Comet: http://www.hakank.org/comet/organize_day.co
  * Gecode: http://hakank.org/gecode/organize_day.cpp

  This model was created by Hakan Kjellerstrand (hakank@gmail.com)
  Also see my other Google CP Solver models:
  http://www.hakank.org/google_or_tools/
"""
from __future__ import print_function
import sys
from ortools.constraint_solver import pywrapcp

#
# No overlapping of tasks s1 and s2
#


def no_overlap(solver, s1, d1, s2, d2):
  b1 = solver.IsLessOrEqualVar(s1 + d1, s2)  # s1 + d1 <= s2
  b2 = solver.IsLessOrEqualVar(s2 + d2, s1)  # s2 + d2 <= s1
  solver.Add(b1 + b2 >= 1)



# Create the solver.
solver = pywrapcp.Solver('Organizing a day')

#
# data
#
n = 4

tasks = list(range(n))
work, mail, shop, bank = tasks
durations = [4, 1, 2, 1]

# task [i,0] must be finished before task [i,1]
before_tasks = [[bank, shop], [mail, work]]

# the valid times of the day
begin = 9
end = 17

#
# declare variables
#
begins = [solver.IntVar(begin, end, 'begins[%i]% % i') for i in tasks]
ends = [solver.IntVar(begin, end, 'ends[%i]% % i') for i in tasks]

#
# constraints
#
for i in tasks:
  solver.Add(ends[i] == begins[i] + durations[i])

for i in tasks:
  for j in tasks:
    if i < j:
      no_overlap(solver, begins[i], durations[i], begins[j], durations[j])

# specific constraints
for (before, after) in before_tasks:
  solver.Add(ends[before] <= begins[after])

solver.Add(begins[work] >= 11)

#
# solution and search
#
db = solver.Phase(begins + ends, solver.INT_VAR_DEFAULT,
                  solver.INT_VALUE_DEFAULT)

solver.NewSearch(db)

num_solutions = 0
while solver.NextSolution():
  num_solutions += 1
  print('begins:', [begins[i].Value() for i in tasks])
  print('ends:', [ends[i].Value() for i in tasks])
  print()

print('num_solutions:', num_solutions)
print('failures:', solver.Failures())
print('branches:', solver.Branches())
print('WallTime:', solver.WallTime(), 'ms')