65 lines
2.8 KiB
C++
65 lines
2.8 KiB
C++
// Copyright 2010-2025 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.
|
|
|
|
#ifndef OR_TOOLS_SAT_CP_MODEL_POSTSOLVE_H_
|
|
#define OR_TOOLS_SAT_CP_MODEL_POSTSOLVE_H_
|
|
|
|
#include <cstdint>
|
|
#include <vector>
|
|
|
|
#include "absl/types/span.h"
|
|
#include "ortools/sat/cp_model.pb.h"
|
|
#include "ortools/util/logging.h"
|
|
#include "ortools/util/sorted_interval_list.h"
|
|
|
|
namespace operations_research {
|
|
namespace sat {
|
|
|
|
// Postsolves the given response using information filled by our presolver.
|
|
//
|
|
// This works as follow:
|
|
// - First we fix fixed variables of the mapping_model according to the solution
|
|
// of the presolved problem and the index mapping.
|
|
// - Then, we process the mapping constraints in "reverse" order, and unit
|
|
// propagate each of them when necessary. By construction this should never
|
|
// give rise to any conflicts. And after each constraints, we should have
|
|
// a feasible solution to the presolved problem + all already postsolved
|
|
// constraints. This is the invariant we maintain.
|
|
// - Finally, we arbitrarily fix any free variables left and update the given
|
|
// response with the new solution.
|
|
//
|
|
// Note: Most of the postsolve operations require the constraints to have been
|
|
// written in the correct way by the presolve.
|
|
//
|
|
// TODO(user): We could use the search strategy to fix free variables to some
|
|
// chosen values? The feature might never be needed though.
|
|
void PostsolveResponse(int64_t num_variables_in_original_model,
|
|
const CpModelProto& mapping_proto,
|
|
absl::Span<const int> postsolve_mapping,
|
|
std::vector<int64_t>* solution);
|
|
|
|
// Try to postsolve with a "best-effort" the reduced domain from the presolved
|
|
// model to the user given model. See the documentation of the CpSolverResponse
|
|
// tightened_variables field for more information on the caveats.
|
|
void FillTightenedDomainInResponse(const CpModelProto& original_model,
|
|
const CpModelProto& mapping_proto,
|
|
absl::Span<const int> postsolve_mapping,
|
|
absl::Span<const Domain> search_domains,
|
|
CpSolverResponse* response,
|
|
SolverLogger* logger);
|
|
|
|
} // namespace sat
|
|
} // namespace operations_research
|
|
|
|
#endif // OR_TOOLS_SAT_CP_MODEL_POSTSOLVE_H_
|