sos2_constraint.h

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// 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.
 
// IWYU pragma: private, include "ortools/math_opt/cpp/math_opt.h"
// IWYU pragma: friend "ortools/math_opt/cpp/.*"
#ifndef OR_TOOLS_MATH_OPT_CONSTRAINTS_SOS_SOS2_CONSTRAINT_H_
#define OR_TOOLS_MATH_OPT_CONSTRAINTS_SOS_SOS2_CONSTRAINT_H_
 
#include <cstdint>
#include <ostream>
#include <string>
#include <vector>
 
#include "absl/strings/string_view.h"
#include "ortools/base/strong_int.h"
#include "ortools/math_opt/constraints/sos/util.h"
#include "ortools/math_opt/constraints/util/model_util.h"
#include "ortools/math_opt/cpp/variable_and_expressions.h"
#include "ortools/math_opt/storage/model_storage.h"
#include "ortools/math_opt/storage/model_storage_item.h"
 
namespace operations_research::math_opt {
 
// A value type that references a SOS2 constraint from ModelStorage.
// Usually this type is passed by copy.
//
// This type implements https://abseil.io/docs/cpp/guides/hash.
class Sos2Constraint final : public ModelStorageItem {
 public:
  // The typed integer used for ids.
  using IdType = Sos2ConstraintId;
 
  inline Sos2Constraint(ModelStorageCPtr storage, Sos2ConstraintId id);
 
  inline int64_t id() const;
 
  inline Sos2ConstraintId typed_id() const;
 
  inline int64_t num_expressions() const;
  LinearExpression Expression(int index) const;
  inline bool has_weights() const;
  inline double weight(int index) const;
  inline absl::string_view name() const;
 
  // All variables that appear in the SOS2 constraint with a nonzero coefficient
  // in any of the expressions. Order is not defined.
  inline std::vector<Variable> NonzeroVariables() const;
 
  // Returns a detailed string description of the contents of the constraint
  // (not its name, use `<<` for that instead).
  inline std::string ToString() const;
 
  friend inline bool operator==(const Sos2Constraint& lhs,
                                const Sos2Constraint& rhs);
  friend inline bool operator!=(const Sos2Constraint& lhs,
                                const Sos2Constraint& rhs);
  template <typename H>
  friend H AbslHashValue(H h, const Sos2Constraint& constraint);
  friend std::ostream& operator<<(std::ostream& ostr,
                                  const Sos2Constraint& constraint);
 
 private:
  Sos2ConstraintId id_;
};
 
// Streams the name of the constraint, as registered upon constraint creation,
// or a short default if none was provided.
inline std::ostream& operator<<(std::ostream& ostr,
                                const Sos2Constraint& constraint);

// Inline function implementations
 
int64_t Sos2Constraint::id() const { return id_.value(); }
 
Sos2ConstraintId Sos2Constraint::typed_id() const { return id_; }
 
int64_t Sos2Constraint::num_expressions() const {
  return storage()->constraint_data(id_).num_expressions();
}
 
bool Sos2Constraint::has_weights() const {
  return storage()->constraint_data(id_).has_weights();
}
 
double Sos2Constraint::weight(int index) const {
  return storage()->constraint_data(id_).weight(index);
}
 
absl::string_view Sos2Constraint::name() const {
  if (storage()->has_constraint(id_)) {
    return storage()->constraint_data(id_).name();
  }
  return kDeletedConstraintDefaultDescription;
}
 
std::vector<Variable> Sos2Constraint::NonzeroVariables() const {
  return AtomicConstraintNonzeroVariables(*storage(), id_);
}
 
bool operator==(const Sos2Constraint& lhs, const Sos2Constraint& rhs) {
  return lhs.id_ == rhs.id_ && lhs.storage() == rhs.storage();
}
 
bool operator!=(const Sos2Constraint& lhs, const Sos2Constraint& rhs) {
  return !(lhs == rhs);
}
 
template <typename H>
H AbslHashValue(H h, const Sos2Constraint& constraint) {
  return H::combine(std::move(h), constraint.id_.value(), constraint.storage());
}
 
std::ostream& operator<<(std::ostream& ostr, const Sos2Constraint& constraint) {
  // TODO(b/170992529): handle quoting of invalid characters in the name.
  const absl::string_view name = constraint.name();
  if (name.empty()) {
    ostr << "__sos2_con#" << constraint.id() << "__";
  } else {
    ostr << name;
  }
  return ostr;
}
 
std::string Sos2Constraint::ToString() const {
  if (storage()->has_constraint(id_)) {
    return internal::SosConstraintToString(*this, "SOS2");
  }
  return std::string(kDeletedConstraintDefaultDescription);
}
 
Sos2Constraint::Sos2Constraint(const ModelStorageCPtr storage,
                               const Sos2ConstraintId id)
    : ModelStorageItem(storage), id_(id) {}
 
}  // namespace operations_research::math_opt
 
#endif  // OR_TOOLS_MATH_OPT_CONSTRAINTS_SOS_SOS2_CONSTRAINT_H_