122 lines
3.2 KiB
Python
122 lines
3.2 KiB
Python
from ortools.constraint_solver import pywrapcp
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from google.apputils import app
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import gflags
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import random
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class OneVarLns(pywrapcp.PyLns):
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"""One Var LNS."""
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def __init__(self, vars):
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pywrapcp.PyLns.__init__(self, vars)
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self.__index = 0
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def InitFragments(self):
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self.__index = 0
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def NextFragment(self):
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if self.__index < self.Size():
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self.__index += 1
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return [self.__index - 1]
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else:
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return []
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class MoveOneVar(pywrapcp.IntVarLocalSearchOperator):
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"""Move one var up or down."""
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def __init__(self, vars):
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pywrapcp.IntVarLocalSearchOperator.__init__(self, vars)
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self.__index = 0
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self.__up = False
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def OneNeighbor(self):
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current_value = self.OldValue(self.__index)
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if self.__up:
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self.SetValue(self.__index, current_value + 1)
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self.__index = (self.__index + 1) % self.Size()
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else:
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self.SetValue(self.__index, current_value - 1)
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self.__up = not self.__up
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return True
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def OnStart(self):
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pass
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def IsIncremental(self):
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return False
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class SumFilter(pywrapcp.IntVarLocalSearchFilter):
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"""Filter to speed up LS computation."""
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def __init__(self, vars):
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pywrapcp.IntVarLocalSearchFilter.__init__(self, vars)
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self.__sum = 0
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def OnSynchronize(self, delta):
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self.__sum = sum(self.Value(index) for index in range(self.Size()))
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def Accept(self, delta, _):
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solution_delta = delta.IntVarContainer()
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solution_delta_size = solution_delta.Size()
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for i in range(solution_delta_size):
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if not solution_delta.Element(i).Activated():
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return True
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new_sum = self.__sum
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for i in range(solution_delta_size):
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element = solution_delta.Element(index)
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touched_var = self.FindIndex(element.Var())
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old_value = self.Value(touched_var)
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new_value = element.Value()
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new_sum += new_value - old_value
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return new_sum < self.__sum
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def IsIncremental(self):
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return False
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def Solve(type):
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solver = pywrapcp.Solver('Solve')
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vars = [solver.IntVar(0, 4) for _ in range(4)]
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sum_var = solver.Sum(vars)
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obj = solver.Minimize(sum_var, 1)
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db = solver.Phase(vars, solver.CHOOSE_FIRST_UNBOUND, solver.ASSIGN_MAX_VALUE)
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ls = None
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if type == 0: # LNS
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print 'Large Neighborhood Search'
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one_var_lns = OneVarLns(vars)
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ls_params = solver.LocalSearchPhaseParameters(one_var_lns, db)
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ls = solver.LocalSearchPhase(vars, db, ls_params)
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elif type == 1: # LS
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print 'Local Search'
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move_one_var = MoveOneVar(vars)
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ls_params = solver.LocalSearchPhaseParameters(move_one_var, db)
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ls = solver.LocalSearchPhase(vars, db, ls_params)
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else:
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print 'Local Search with Filter'
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move_one_var = MoveOneVar(vars)
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sum_filter = SumFilter(vars)
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ls_params = solver.LocalSearchPhaseParameters(move_one_var, db, None,
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[sum_filter])
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ls = solver.LocalSearchPhase(vars, db, ls_params)
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collector = solver.LastSolutionCollector()
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collector.Add(vars)
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collector.AddObjective(sum_var)
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log = solver.SearchLog(1000, obj)
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solver.Solve(ls, [collector, obj, log])
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print 'Objective value = %d' % collector.ObjectiveValue(0)
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def main(_):
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Solve(0)
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Solve(1)
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Solve(2)
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if __name__ == '__main__':
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app.run()
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