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csls_api.cs
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csls_api.cs
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// Copyright 2010-2021 Google LLC
// 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.
using System;
using Google.OrTools.ConstraintSolver;
/**
* Shows how to write a custom lns operator.
*/
public class OneVarLns : BaseLns
{
public OneVarLns(IntVar[] vars) : base(vars)
{
}
public override void InitFragments()
{
index_ = 0;
}
public override bool NextFragment()
{
int size = Size();
if (index_ < size)
{
AppendToFragment(index_);
++index_;
return true;
}
else
{
return false;
}
}
private int index_;
}
class MoveOneVar : IntVarLocalSearchOperator
{
public MoveOneVar(IntVar[] variables) : base(variables)
{
variable_index_ = 0;
move_up_ = false;
}
protected override bool MakeOneNeighbor()
{
long current_value = OldValue(variable_index_);
if (move_up_)
{
SetValue(variable_index_, current_value + 1);
variable_index_ = (variable_index_ + 1) % Size();
}
else
{
SetValue(variable_index_, current_value - 1);
}
move_up_ = !move_up_;
return true;
}
// Index of the next variable to try to restore
private long variable_index_;
// Direction of the modification.
private bool move_up_;
};
public class SumFilter : IntVarLocalSearchFilter
{
public SumFilter(IntVar[] vars) : base(vars)
{
sum_ = 0;
}
protected override void OnSynchronize(Assignment delta)
{
sum_ = 0;
for (int index = 0; index < Size(); ++index)
{
sum_ += Value(index);
}
}
public override bool Accept(Assignment delta, Assignment unused_deltadelta, long unused_objective_min,
long unused_objective_max)
{
AssignmentIntContainer solution_delta = delta.IntVarContainer();
int solution_delta_size = solution_delta.Size();
for (int i = 0; i < solution_delta_size; ++i)
{
if (!solution_delta.Element(i).Activated())
{
return true;
}
}
long new_sum = sum_;
for (int index = 0; index < solution_delta_size; ++index)
{
int touched_var = Index(solution_delta.Element(index).Var());
long old_value = Value(touched_var);
long new_value = solution_delta.Element(index).Value();
new_sum += new_value - old_value;
}
return new_sum < sum_;
}
private long sum_;
};
public class CsLsApi
{
private static void BasicLns()
{
Console.WriteLine("BasicLns");
Solver solver = new Solver("BasicLns");
IntVar[] vars = solver.MakeIntVarArray(4, 0, 4, "vars");
IntVar sum_var = vars.Sum().Var();
OptimizeVar obj = sum_var.Minimize(1);
DecisionBuilder db = solver.MakePhase(vars, Solver.CHOOSE_FIRST_UNBOUND, Solver.ASSIGN_MAX_VALUE);
OneVarLns one_var_lns = new OneVarLns(vars);
LocalSearchPhaseParameters ls_params = solver.MakeLocalSearchPhaseParameters(sum_var, one_var_lns, db);
DecisionBuilder ls = solver.MakeLocalSearchPhase(vars, db, ls_params);
SolutionCollector collector = solver.MakeLastSolutionCollector();
collector.AddObjective(sum_var);
SearchMonitor log = solver.MakeSearchLog(1000, obj);
solver.Solve(ls, collector, obj, log);
Console.WriteLine("Objective value = {0}", collector.ObjectiveValue(0));
}
private static void BasicLs()
{
Console.WriteLine("BasicLs");
Solver solver = new Solver("BasicLs");
IntVar[] vars = solver.MakeIntVarArray(4, 0, 4, "vars");
IntVar sum_var = vars.Sum().Var();
OptimizeVar obj = sum_var.Minimize(1);
DecisionBuilder db = solver.MakePhase(vars, Solver.CHOOSE_FIRST_UNBOUND, Solver.ASSIGN_MAX_VALUE);
MoveOneVar move_one_var = new MoveOneVar(vars);
LocalSearchPhaseParameters ls_params = solver.MakeLocalSearchPhaseParameters(sum_var, move_one_var, db);
DecisionBuilder ls = solver.MakeLocalSearchPhase(vars, db, ls_params);
SolutionCollector collector = solver.MakeLastSolutionCollector();
collector.AddObjective(sum_var);
SearchMonitor log = solver.MakeSearchLog(1000, obj);
solver.Solve(ls, collector, obj, log);
Console.WriteLine("Objective value = {0}", collector.ObjectiveValue(0));
}
private static void BasicLsWithFilter()
{
Console.WriteLine("BasicLsWithFilter");
Solver solver = new Solver("BasicLs");
IntVar[] vars = solver.MakeIntVarArray(4, 0, 4, "vars");
IntVar sum_var = vars.Sum().Var();
OptimizeVar obj = sum_var.Minimize(1);
DecisionBuilder db = solver.MakePhase(vars, Solver.CHOOSE_FIRST_UNBOUND, Solver.ASSIGN_MAX_VALUE);
MoveOneVar move_one_var = new MoveOneVar(vars);
SumFilter filter = new SumFilter(vars);
IntVarLocalSearchFilter[] filters = new IntVarLocalSearchFilter[] { filter };
LocalSearchFilterManager filter_manager = new LocalSearchFilterManager(filters);
LocalSearchPhaseParameters ls_params =
solver.MakeLocalSearchPhaseParameters(sum_var, move_one_var, db, null, filter_manager);
DecisionBuilder ls = solver.MakeLocalSearchPhase(vars, db, ls_params);
SolutionCollector collector = solver.MakeLastSolutionCollector();
collector.AddObjective(sum_var);
SearchMonitor log = solver.MakeSearchLog(1000, obj);
solver.Solve(ls, collector, obj, log);
Console.WriteLine("Objective value = {0}", collector.ObjectiveValue(0));
}
public static void Main(String[] args)
{
BasicLns();
BasicLs();
BasicLsWithFilter();
}
}