78 lines
2.8 KiB
C++
78 lines
2.8 KiB
C++
// Copyright 2010-2022 Google LLC
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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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// This file contains some BopOptimizerBase implementations that are "complete"
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// solvers. That is, they work on the full problem, and can solve the problem
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// (and prove optimality) by themselves. Moreover, they can be run for short
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// period of time and resumed later from the state they where left off.
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//
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// The idea is that it is worthwhile spending some time in these algorithms,
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// because in some situation they can improve the current upper/lower bound or
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// even solve the problem to optimality.
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//
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// Note(user): The GuidedSatFirstSolutionGenerator can also be used as a
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// complete SAT solver provided that we keep running it after it has found a
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// first solution. This is the default behavior of the kNotGuided policy.
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#ifndef OR_TOOLS_BOP_COMPLETE_OPTIMIZER_H_
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#define OR_TOOLS_BOP_COMPLETE_OPTIMIZER_H_
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#include <cstdint>
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#include <deque>
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#include <string>
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#include <vector>
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#include "ortools/bop/bop_base.h"
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#include "ortools/bop/bop_solution.h"
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#include "ortools/bop/bop_types.h"
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#include "ortools/sat/boolean_problem.pb.h"
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#include "ortools/sat/encoding.h"
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#include "ortools/sat/sat_solver.h"
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namespace operations_research {
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namespace bop {
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// TODO(user): Merge this with the code in sat/optimization.cc
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class SatCoreBasedOptimizer : public BopOptimizerBase {
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public:
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explicit SatCoreBasedOptimizer(const std::string& name);
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~SatCoreBasedOptimizer() override;
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protected:
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bool ShouldBeRun(const ProblemState& problem_state) const override;
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Status Optimize(const BopParameters& parameters,
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const ProblemState& problem_state, LearnedInfo* learned_info,
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TimeLimit* time_limit) override;
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private:
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BopOptimizerBase::Status SynchronizeIfNeeded(
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const ProblemState& problem_state);
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sat::SatSolver::Status SolveWithAssumptions();
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int64_t state_update_stamp_;
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bool initialized_;
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bool assumptions_already_added_;
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sat::SatSolver solver_;
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sat::Coefficient offset_;
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sat::Coefficient lower_bound_;
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sat::Coefficient upper_bound_;
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sat::Coefficient stratified_lower_bound_;
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std::deque<sat::EncodingNode> repository_;
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std::vector<sat::EncodingNode*> nodes_;
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};
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} // namespace bop
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} // namespace operations_research
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#endif // OR_TOOLS_BOP_COMPLETE_OPTIMIZER_H_
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