121 lines
3.1 KiB
Python
121 lines
3.1 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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Organizing a day in Google CP Solver.
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Simple scheduling problem.
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Problem formulation from ECLiPSe:
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Slides on (Finite Domain) Constraint Logic Programming, page 38f
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http://eclipse-clp.org/reports/eclipse.ppt
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Compare with the following models:
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* MiniZinc: http://www.hakank.org/minizinc/organize_day.mzn
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* Comet: http://www.hakank.org/comet/organize_day.co
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* Gecode: http://hakank.org/gecode/organize_day.cpp
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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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import sys
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from constraint_solver import pywrapcp
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#
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# No overlapping of tasks s1 and s2
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#
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def no_overlap(solver, s1, d1, s2, d2):
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b1 = solver.MakeIsLessOrEqualVar(s1 + d1, s2) # s1 + d1 <= s2
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b2 = solver.MakeIsLessOrEqualVar(s2 + d2, s1) # s2 + d2 <= s1
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solver.Add(b1 + b2 >= 1)
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def main():
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# Create the solver.
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solver = pywrapcp.Solver('Organizing a day')
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#
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# data
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#
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n = 4
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tasks = range(n)
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work, mail, shop, bank = tasks
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durations = [4,1,2,1]
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# task [i,0] must be finished before task [i,1]
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before_tasks = [
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[bank, shop],
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[mail, work]
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]
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# the valid times of the day
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begin = 9
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end = 17
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#
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# declare variables
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#
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begins = [solver.IntVar(begin, end, 'begins[%i]% % i') for i in tasks]
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ends = [solver.IntVar(begin, end, 'ends[%i]% % i') for i in tasks]
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#
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# constraints
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#
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for i in tasks:
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solver.Add(ends[i] == begins[i] + durations[i])
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for i in tasks:
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for j in tasks:
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if i < j:
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no_overlap(solver,
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begins[i], durations[i],
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begins[j], durations[j])
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# specific constraints
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for (before, after) in before_tasks:
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solver.Add(ends[before] <= begins[after])
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solver.Add(begins[work] >= 11)
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#
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# solution and search
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#
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db = solver.Phase(begins + ends,
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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 'begins:', [begins[i].Value() for i in tasks]
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print 'ends:', [ends[i].Value() for i in tasks]
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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(), 'ms'
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if __name__ == '__main__':
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main()
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