90 lines
3.3 KiB
C++
90 lines
3.3 KiB
C++
// Copyright 2010-2018 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_RINS_H_
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#define OR_TOOLS_SAT_RINS_H_
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#include <vector>
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#include "absl/container/flat_hash_map.h"
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#include "absl/synchronization/mutex.h"
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#include "absl/types/optional.h"
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#include "ortools/sat/integer.h"
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#include "ortools/sat/linear_programming_constraint.h"
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#include "ortools/sat/model.h"
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#include "ortools/sat/synchronization.h"
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namespace operations_research {
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namespace sat {
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// Links IntegerVariable with model variable and its lp constraint if any.
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struct LPVariable {
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IntegerVariable positive_var = kNoIntegerVariable;
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LinearProgrammingConstraint *lp = nullptr;
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int model_var;
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bool operator==(const LPVariable other) const {
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return (positive_var == other.positive_var && lp == other.lp &&
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model_var == other.model_var);
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}
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};
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// This is used to "cache" in the model the set of relevant LPVariable.
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struct LPVariables {
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std::vector<LPVariable> vars;
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int model_vars_size = 0;
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};
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// A RINS Neighborhood is actually just a generic neighborhood where the domain
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// of some variable have been reduced (fixed or restricted in [lb, ub]).
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//
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// Important: It might be possible that the value of the variables here are
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// outside the domains of these variables! This happens for RENS type of
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// neighborhood in the presence of holes in the domains because the LP
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// relaxation ignore those.
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struct RINSNeighborhood {
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// A variable will appear only once and not in both vectors.
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std::vector<std::pair</*model_var*/ int, /*value*/ int64> > fixed_vars;
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std::vector<
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std::pair</*model_var*/ int, /*domain*/ std::pair<int64, int64> > >
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reduced_domain_vars;
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};
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// Helper method to create a RINS neighborhood by fixing variables with same
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// values in relaxation solution and the current best solution in the
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// response_manager. Prioritizes repositories in following order to get a
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// relaxation solution.
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// 1. incomplete_solutions
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// 2. lp_solutions
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// 3. relaxation_solutions
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//
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// If response_manager is not provided, this generates a RENS neighborhood by
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// ignoring the solutions and using the relaxation values. The domain of the
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// variables are reduced to integer values around relaxation values. If the
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// relaxation value is integer, then we fix the domain of the variable to that
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// value.
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RINSNeighborhood GetRINSNeighborhood(
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const SharedResponseManager *response_manager,
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const SharedRelaxationSolutionRepository *relaxation_solutions,
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const SharedLPSolutionRepository *lp_solutions,
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SharedIncompleteSolutionManager *incomplete_solutions,
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random_engine_t *random);
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// Adds the current LP solution to the pool.
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void RecordLPRelaxationValues(Model *model);
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} // namespace sat
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} // namespace operations_research
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#endif // OR_TOOLS_SAT_RINS_H_
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