153 lines
4.7 KiB
C++
153 lines
4.7 KiB
C++
// Copyright 2010-2025 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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#ifndef OR_TOOLS_SAT_SHAVING_SOLVER_H_
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#define OR_TOOLS_SAT_SHAVING_SOLVER_H_
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#include <atomic>
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#include <cstdint>
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#include <functional>
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#include <memory>
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#include <string>
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#include <vector>
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#include "absl/base/thread_annotations.h"
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#include "absl/synchronization/mutex.h"
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#include "ortools/sat/cp_model.pb.h"
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#include "ortools/sat/cp_model_lns.h"
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#include "ortools/sat/cp_model_solver_helpers.h"
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#include "ortools/sat/integer_base.h"
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#include "ortools/sat/model.h"
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#include "ortools/sat/sat_parameters.pb.h"
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#include "ortools/sat/subsolver.h"
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#include "ortools/util/sorted_interval_list.h"
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namespace operations_research {
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namespace sat {
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class ObjectiveShavingSolver : public SubSolver {
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public:
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ObjectiveShavingSolver(const SatParameters& local_parameters,
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NeighborhoodGeneratorHelper* helper,
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SharedClasses* shared);
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~ObjectiveShavingSolver() override;
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bool TaskIsAvailable() override;
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std::function<void()> GenerateTask(int64_t task_id) override;
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void Synchronize() override;
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private:
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std::string Info();
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bool ResetAndSolveModel(int64_t task_id);
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// This is fixed at construction.
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SatParameters local_params_;
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NeighborhoodGeneratorHelper* helper_;
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SharedClasses* shared_;
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// Allow to control the local time limit in addition to a potential user
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// defined external Boolean.
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std::atomic<bool> stop_current_chunk_;
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// Local singleton repository and presolved local model.
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std::unique_ptr<Model> local_sat_model_;
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CpModelProto local_proto_;
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// For postsolving a feasible solution or improving objective lb.
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std::vector<int> postsolve_mapping_;
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CpModelProto mapping_proto_;
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absl::Mutex mutex_;
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IntegerValue objective_lb_ ABSL_GUARDED_BY(mutex_);
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IntegerValue objective_ub_ ABSL_GUARDED_BY(mutex_);
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IntegerValue current_objective_target_ub_ ABSL_GUARDED_BY(mutex_);
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bool task_in_flight_ ABSL_GUARDED_BY(mutex_) = false;
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};
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class VariablesShavingSolver : public SubSolver {
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public:
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struct State {
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int var_index;
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bool minimize;
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// We have two modes:
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// - When "shave_using_objective" is true, we shave by minimizing the value
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// of a variable.
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// - When false, we restrict its domain and detect feasible/infeasible.
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Domain reduced_domain;
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bool shave_using_objective = false;
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};
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VariablesShavingSolver(const SatParameters& local_parameters,
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NeighborhoodGeneratorHelper* helper,
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SharedClasses* shared);
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~VariablesShavingSolver() override;
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bool TaskIsAvailable() override;
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void ProcessLocalResponse(const CpSolverResponse& local_response,
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const State& state);
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std::function<void()> GenerateTask(int64_t task_id) override;
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void Synchronize() override;
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private:
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std::string Info();
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int64_t DomainSize(int var) const ABSL_SHARED_LOCKS_REQUIRED(mutex_);
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bool VarIsFixed(int int_var) const ABSL_SHARED_LOCKS_REQUIRED(mutex_);
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bool ConstraintIsInactive(int c) const ABSL_SHARED_LOCKS_REQUIRED(mutex_);
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bool FindNextVar(State* state) ABSL_SHARED_LOCKS_REQUIRED(mutex_);
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void CopyModelConnectedToVar(State* state, Model* local_model,
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CpModelProto* shaving_proto,
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bool* has_no_overlap_2d)
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ABSL_SHARED_LOCKS_REQUIRED(mutex_);
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bool ResetAndSolveModel(int64_t task_id, State* state, Model* local_model,
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CpModelProto* shaving_proto);
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// This is fixed at construction.
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SatParameters local_params_;
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SharedClasses* shared_;
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int shared_bounds_id_ = -1;
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// Allow to control the local time limit in addition to a potential user
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// defined external Boolean.
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std::atomic<bool> stop_current_chunk_;
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const CpModelProto& model_proto_;
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absl::Mutex mutex_;
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int64_t current_index_ = -1;
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std::vector<Domain> var_domains_ ABSL_GUARDED_BY(mutex_);
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// Stats.
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int num_vars_tried_ ABSL_GUARDED_BY(mutex_) = 0;
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int num_vars_shaved_ ABSL_GUARDED_BY(mutex_) = 0;
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int num_infeasible_found_ ABSL_GUARDED_BY(mutex_) = 0;
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};
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} // namespace sat
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} // namespace operations_research
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#endif // OR_TOOLS_SAT_SHAVING_SOLVER_H_
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