constraint_solveri.h

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// Copyright 2010-2018 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_CONSTRAINT_SOLVER_CONSTRAINT_SOLVERI_H_
#define OR_TOOLS_CONSTRAINT_SOLVER_CONSTRAINT_SOLVERI_H_
 
#include <algorithm>
#include <cmath>
#include <cstddef>
#include <functional>
#include <memory>
#include <string>
#include <vector>
 
#include "absl/container/flat_hash_map.h"
#include "absl/strings/str_cat.h"
#include "absl/strings/str_format.h"
#include "absl/strings/str_join.h"
#include "ortools/base/commandlineflags.h"
#include "ortools/base/hash.h"
#include "ortools/base/integral_types.h"
#include "ortools/base/logging.h"
#include "ortools/base/map_util.h"
#include "ortools/base/sysinfo.h"
#include "ortools/base/timer.h"
#include "ortools/constraint_solver/constraint_solver.h"
#include "ortools/util/bitset.h"
#include "ortools/util/tuple_set.h"
#include "ortools/util/vector_map.h"
 
class WallTimer;
 
namespace operations_research {
class CPArgumentProto;
class CPConstraintProto;
class CPIntegerExpressionProto;
class CPIntervalVariableProto;
 
class BaseIntExpr : public IntExpr {
 public:
  explicit BaseIntExpr(Solver* const s) : IntExpr(s), var_(nullptr) {}
  ~BaseIntExpr() override {}
 
  IntVar* Var() override;
  virtual IntVar* CastToVar();
 
 private:
  IntVar* var_;
};
 
enum VarTypes {
  UNSPECIFIED,
  DOMAIN_INT_VAR,
  BOOLEAN_VAR,
  CONST_VAR,
  VAR_ADD_CST,
  VAR_TIMES_CST,
  CST_SUB_VAR,
  OPP_VAR,
  TRACE_VAR
};
 
#ifndef SWIG
template <class T>
class SimpleRevFIFO {
 private:
  enum { CHUNK_SIZE = 16 };  // TODO(user): could be an extra template param
  struct Chunk {
    T data_[CHUNK_SIZE];
    const Chunk* const next_;
    explicit Chunk(const Chunk* next) : next_(next) {}
  };
 
 public:
  class Iterator {
   public:
    explicit Iterator(const SimpleRevFIFO<T>* l)
        : chunk_(l->chunks_), value_(l->Last()) {}
    bool ok() const { return (value_ != nullptr); }
    T operator*() const { return *value_; }
    void operator++() {
      ++value_;
      if (value_ == chunk_->data_ + CHUNK_SIZE) {
        chunk_ = chunk_->next_;
        value_ = chunk_ ? chunk_->data_ : nullptr;
      }
    }
 
   private:
    const Chunk* chunk_;
    const T* value_;
  };
 
  SimpleRevFIFO() : chunks_(nullptr), pos_(0) {}
 
  void Push(Solver* const s, T val) {
    if (pos_.Value() == 0) {
      Chunk* const chunk = s->UnsafeRevAlloc(new Chunk(chunks_));
      s->SaveAndSetValue(reinterpret_cast<void**>(&chunks_),
                         reinterpret_cast<void*>(chunk));
      pos_.SetValue(s, CHUNK_SIZE - 1);
    } else {
      pos_.Decr(s);
    }
    chunks_->data_[pos_.Value()] = val;
  }
 
  void PushIfNotTop(Solver* const s, T val) {
    if (chunks_ == nullptr || LastValue() != val) {
      Push(s, val);
    }
  }
 
  const T* Last() const {
    return chunks_ ? &chunks_->data_[pos_.Value()] : nullptr;
  }
 
  T* MutableLast() { return chunks_ ? &chunks_->data_[pos_.Value()] : nullptr; }
 
  const T& LastValue() const {
    DCHECK(chunks_);
    return chunks_->data_[pos_.Value()];
  }
 
  void SetLastValue(const T& v) {
    DCHECK(Last());
    chunks_->data_[pos_.Value()] = v;
  }
 
 private:
  Chunk* chunks_;
  NumericalRev<int> pos_;
};
 
// TODO(user): use murmurhash.
inline uint64 Hash1(uint64 value) {
  value = (~value) + (value << 21);  
  value ^= value >> 24;
  value += (value << 3) + (value << 8);  
  value ^= value >> 14;
  value += (value << 2) + (value << 4);  
  value ^= value >> 28;
  value += (value << 31);
  return value;
}
 
inline uint64 Hash1(uint32 value) {
  uint64 a = value;
  a = (a + 0x7ed55d16) + (a << 12);
  a = (a ^ 0xc761c23c) ^ (a >> 19);
  a = (a + 0x165667b1) + (a << 5);
  a = (a + 0xd3a2646c) ^ (a << 9);
  a = (a + 0xfd7046c5) + (a << 3);
  a = (a ^ 0xb55a4f09) ^ (a >> 16);
  return a;
}
 
inline uint64 Hash1(int64 value) { return Hash1(static_cast<uint64>(value)); }
 
inline uint64 Hash1(int value) { return Hash1(static_cast<uint32>(value)); }
 
inline uint64 Hash1(void* const ptr) {
#if defined(ARCH_K8) || defined(__powerpc64__) || defined(__aarch64__)
  return Hash1(reinterpret_cast<uint64>(ptr));
#else
  return Hash1(reinterpret_cast<uint32>(ptr));
#endif
}
 
template <class T>
uint64 Hash1(const std::vector<T*>& ptrs) {
  if (ptrs.empty()) {
    return 0;
  } else if (ptrs.size() == 1) {
    return Hash1(ptrs[0]);
  } else {
    uint64 hash = Hash1(ptrs[0]);
    for (int i = 1; i < ptrs.size(); ++i) {
      hash = hash * i + Hash1(ptrs[i]);
    }
    return hash;
  }
}
 
inline uint64 Hash1(const std::vector<int64>& ptrs) {
  if (ptrs.empty()) {
    return 0;
  } else if (ptrs.size() == 1) {
    return Hash1(ptrs[0]);
  } else {
    uint64 hash = Hash1(ptrs[0]);
    for (int i = 1; i < ptrs.size(); ++i) {
      hash = hash * i + Hash1(ptrs[i]);
    }
    return hash;
  }
}
 
template <class K, class V>
class RevImmutableMultiMap {
 public:
  RevImmutableMultiMap(Solver* const solver, int initial_size)
      : solver_(solver),
        array_(solver->UnsafeRevAllocArray(new Cell*[initial_size])),
        size_(initial_size),
        num_items_(0) {
    memset(array_, 0, sizeof(*array_) * size_.Value());
  }
 
  ~RevImmutableMultiMap() {}
 
  int num_items() const { return num_items_.Value(); }
 
  bool ContainsKey(const K& key) const {
    uint64 code = Hash1(key) % size_.Value();
    Cell* tmp = array_[code];
    while (tmp) {
      if (tmp->key() == key) {
        return true;
      }
      tmp = tmp->next();
    }
    return false;
  }
 
  const V& FindWithDefault(const K& key, const V& default_value) const {
    uint64 code = Hash1(key) % size_.Value();
    Cell* tmp = array_[code];
    while (tmp) {
      if (tmp->key() == key) {
        return tmp->value();
      }
      tmp = tmp->next();
    }
    return default_value;
  }
 
  void Insert(const K& key, const V& value) {
    const int position = Hash1(key) % size_.Value();
    Cell* const cell =
        solver_->UnsafeRevAlloc(new Cell(key, value, array_[position]));
    solver_->SaveAndSetValue(reinterpret_cast<void**>(&array_[position]),
                             reinterpret_cast<void*>(cell));
    num_items_.Incr(solver_);
    if (num_items_.Value() > 2 * size_.Value()) {
      Double();
    }
  }
 
 private:
  class Cell {
   public:
    Cell(const K& key, const V& value, Cell* const next)
        : key_(key), value_(value), next_(next) {}
 
    void SetRevNext(Solver* const solver, Cell* const next) {
      solver->SaveAndSetValue(reinterpret_cast<void**>(&next_),
                              reinterpret_cast<void*>(next));
    }
 
    Cell* next() const { return next_; }
 
    const K& key() const { return key_; }
 
    const V& value() const { return value_; }
 
   private:
    const K key_;
    const V value_;
    Cell* next_;
  };
 
  void Double() {
    Cell** const old_cell_array = array_;
    const int old_size = size_.Value();
    size_.SetValue(solver_, size_.Value() * 2);
    solver_->SaveAndSetValue(
        reinterpret_cast<void**>(&array_),
        reinterpret_cast<void*>(
            solver_->UnsafeRevAllocArray(new Cell*[size_.Value()])));
    memset(array_, 0, size_.Value() * sizeof(*array_));
    for (int i = 0; i < old_size; ++i) {
      Cell* tmp = old_cell_array[i];
      while (tmp != nullptr) {
        Cell* const to_reinsert = tmp;
        tmp = tmp->next();
        const uint64 new_position = Hash1(to_reinsert->key()) % size_.Value();
        to_reinsert->SetRevNext(solver_, array_[new_position]);
        solver_->SaveAndSetValue(
            reinterpret_cast<void**>(&array_[new_position]),
            reinterpret_cast<void*>(to_reinsert));
      }
    }
  }
 
  Solver* const solver_;
  Cell** array_;
  NumericalRev<int> size_;
  NumericalRev<int> num_items_;
};
 
class RevSwitch {
 public:
  RevSwitch() : value_(false) {}
 
  bool Switched() const { return value_; }
 
  void Switch(Solver* const solver) { solver->SaveAndSetValue(&value_, true); }
 
 private:
  bool value_;
};
 
class SmallRevBitSet {
 public:
  explicit SmallRevBitSet(int64 size);
  void SetToOne(Solver* const solver, int64 pos);
  void SetToZero(Solver* const solver, int64 pos);
  int64 Cardinality() const;
  bool IsCardinalityZero() const { return bits_.Value() == GG_ULONGLONG(0); }
  bool IsCardinalityOne() const {
    return (bits_.Value() != 0) && !(bits_.Value() & (bits_.Value() - 1));
  }
  int64 GetFirstOne() const;
 
 private:
  Rev<uint64> bits_;
};
 
class RevBitSet {
 public:
  explicit RevBitSet(int64 size);
  ~RevBitSet();
 
  void SetToOne(Solver* const solver, int64 index);
  void SetToZero(Solver* const solver, int64 index);
  bool IsSet(int64 index) const;
  int64 Cardinality() const;
  bool IsCardinalityZero() const;
  bool IsCardinalityOne() const;
  int64 GetFirstBit(int start) const;
  void ClearAll(Solver* const solver);
 
  friend class RevBitMatrix;
 
 private:
  void Save(Solver* const solver, int offset);
  const int64 size_;
  const int64 length_;
  uint64* bits_;
  uint64* stamps_;
};
 
class RevBitMatrix : private RevBitSet {
 public:
  RevBitMatrix(int64 rows, int64 columns);
  ~RevBitMatrix();
 
  void SetToOne(Solver* const solver, int64 row, int64 column);
  void SetToZero(Solver* const solver, int64 row, int64 column);
  bool IsSet(int64 row, int64 column) const {
    DCHECK_GE(row, 0);
    DCHECK_LT(row, rows_);
    DCHECK_GE(column, 0);
    DCHECK_LT(column, columns_);
    return RevBitSet::IsSet(row * columns_ + column);
  }
  int64 Cardinality(int row) const;
  bool IsCardinalityZero(int row) const;
  bool IsCardinalityOne(int row) const;
  int64 GetFirstBit(int row, int start) const;
  void ClearAll(Solver* const solver);
 
 private:
  const int64 rows_;
  const int64 columns_;
};
 
 
template <class T>
class CallMethod0 : public Demon {
 public:
  CallMethod0(T* const ct, void (T::*method)(), const std::string& name)
      : constraint_(ct), method_(method), name_(name) {}
 
  ~CallMethod0() override {}
 
  void Run(Solver* const s) override { (constraint_->*method_)(); }
 
  std::string DebugString() const override {
    return "CallMethod_" + name_ + "(" + constraint_->DebugString() + ")";
  }
 
 private:
  T* const constraint_;
  void (T::*const method_)();
  const std::string name_;
};
 
template <class T>
Demon* MakeConstraintDemon0(Solver* const s, T* const ct, void (T::*method)(),
                            const std::string& name) {
  return s->RevAlloc(new CallMethod0<T>(ct, method, name));
}
 
template <class P>
std::string ParameterDebugString(P param) {
  return absl::StrCat(param);
}
 
template <class P>
std::string ParameterDebugString(P* param) {
  return param->DebugString();
}
 
template <class T, class P>
class CallMethod1 : public Demon {
 public:
  CallMethod1(T* const ct, void (T::*method)(P), const std::string& name,
              P param1)
      : constraint_(ct), method_(method), name_(name), param1_(param1) {}
 
  ~CallMethod1() override {}
 
  void Run(Solver* const s) override { (constraint_->*method_)(param1_); }
 
  std::string DebugString() const override {
    return absl::StrCat("CallMethod_", name_, "(", constraint_->DebugString(),
                        ", ", ParameterDebugString(param1_), ")");
  }
 
 private:
  T* const constraint_;
  void (T::*const method_)(P);
  const std::string name_;
  P param1_;
};
 
template <class T, class P>
Demon* MakeConstraintDemon1(Solver* const s, T* const ct, void (T::*method)(P),
                            const std::string& name, P param1) {
  return s->RevAlloc(new CallMethod1<T, P>(ct, method, name, param1));
}
 
template <class T, class P, class Q>
class CallMethod2 : public Demon {
 public:
  CallMethod2(T* const ct, void (T::*method)(P, Q), const std::string& name,
              P param1, Q param2)
      : constraint_(ct),
        method_(method),
        name_(name),
        param1_(param1),
        param2_(param2) {}
 
  ~CallMethod2() override {}
 
  void Run(Solver* const s) override {
    (constraint_->*method_)(param1_, param2_);
  }
 
  std::string DebugString() const override {
    return absl::StrCat(absl::StrCat("CallMethod_", name_),
                        absl::StrCat("(", constraint_->DebugString()),
                        absl::StrCat(", ", ParameterDebugString(param1_)),
                        absl::StrCat(", ", ParameterDebugString(param2_), ")"));
  }
 
 private:
  T* const constraint_;
  void (T::*const method_)(P, Q);
  const std::string name_;
  P param1_;
  Q param2_;
};
 
template <class T, class P, class Q>
Demon* MakeConstraintDemon2(Solver* const s, T* const ct,
                            void (T::*method)(P, Q), const std::string& name,
                            P param1, Q param2) {
  return s->RevAlloc(
      new CallMethod2<T, P, Q>(ct, method, name, param1, param2));
}
template <class T, class P, class Q, class R>
class CallMethod3 : public Demon {
 public:
  CallMethod3(T* const ct, void (T::*method)(P, Q, R), const std::string& name,
              P param1, Q param2, R param3)
      : constraint_(ct),
        method_(method),
        name_(name),
        param1_(param1),
        param2_(param2),
        param3_(param3) {}
 
  ~CallMethod3() override {}
 
  void Run(Solver* const s) override {
    (constraint_->*method_)(param1_, param2_, param3_);
  }
 
  std::string DebugString() const override {
    return absl::StrCat(absl::StrCat("CallMethod_", name_),
                        absl::StrCat("(", constraint_->DebugString()),
                        absl::StrCat(", ", ParameterDebugString(param1_)),
                        absl::StrCat(", ", ParameterDebugString(param2_)),
                        absl::StrCat(", ", ParameterDebugString(param3_), ")"));
  }
 
 private:
  T* const constraint_;
  void (T::*const method_)(P, Q, R);
  const std::string name_;
  P param1_;
  Q param2_;
  R param3_;
};
 
template <class T, class P, class Q, class R>
Demon* MakeConstraintDemon3(Solver* const s, T* const ct,
                            void (T::*method)(P, Q, R), const std::string& name,
                            P param1, Q param2, R param3) {
  return s->RevAlloc(
      new CallMethod3<T, P, Q, R>(ct, method, name, param1, param2, param3));
}
 
 
template <class T>
class DelayedCallMethod0 : public Demon {
 public:
  DelayedCallMethod0(T* const ct, void (T::*method)(), const std::string& name)
      : constraint_(ct), method_(method), name_(name) {}
 
  ~DelayedCallMethod0() override {}
 
  void Run(Solver* const s) override { (constraint_->*method_)(); }
 
  Solver::DemonPriority priority() const override {
    return Solver::DELAYED_PRIORITY;
  }
 
  std::string DebugString() const override {
    return "DelayedCallMethod_" + name_ + "(" + constraint_->DebugString() +
           ")";
  }
 
 private:
  T* const constraint_;
  void (T::*const method_)();
  const std::string name_;
};
 
template <class T>
Demon* MakeDelayedConstraintDemon0(Solver* const s, T* const ct,
                                   void (T::*method)(),
                                   const std::string& name) {
  return s->RevAlloc(new DelayedCallMethod0<T>(ct, method, name));
}
 
template <class T, class P>
class DelayedCallMethod1 : public Demon {
 public:
  DelayedCallMethod1(T* const ct, void (T::*method)(P), const std::string& name,
                     P param1)
      : constraint_(ct), method_(method), name_(name), param1_(param1) {}
 
  ~DelayedCallMethod1() override {}
 
  void Run(Solver* const s) override { (constraint_->*method_)(param1_); }
 
  Solver::DemonPriority priority() const override {
    return Solver::DELAYED_PRIORITY;
  }
 
  std::string DebugString() const override {
    return absl::StrCat("DelayedCallMethod_", name_, "(",
                        constraint_->DebugString(), ", ",
                        ParameterDebugString(param1_), ")");
  }
 
 private:
  T* const constraint_;
  void (T::*const method_)(P);
  const std::string name_;
  P param1_;
};
 
template <class T, class P>
Demon* MakeDelayedConstraintDemon1(Solver* const s, T* const ct,
                                   void (T::*method)(P),
                                   const std::string& name, P param1) {
  return s->RevAlloc(new DelayedCallMethod1<T, P>(ct, method, name, param1));
}
 
template <class T, class P, class Q>
class DelayedCallMethod2 : public Demon {
 public:
  DelayedCallMethod2(T* const ct, void (T::*method)(P, Q),
                     const std::string& name, P param1, Q param2)
      : constraint_(ct),
        method_(method),
        name_(name),
        param1_(param1),
        param2_(param2) {}
 
  ~DelayedCallMethod2() override {}
 
  void Run(Solver* const s) override {
    (constraint_->*method_)(param1_, param2_);
  }
 
  Solver::DemonPriority priority() const override {
    return Solver::DELAYED_PRIORITY;
  }
 
  std::string DebugString() const override {
    return absl::StrCat(absl::StrCat("DelayedCallMethod_", name_),
                        absl::StrCat("(", constraint_->DebugString()),
                        absl::StrCat(", ", ParameterDebugString(param1_)),
                        absl::StrCat(", ", ParameterDebugString(param2_), ")"));
  }
 
 private:
  T* const constraint_;
  void (T::*const method_)(P, Q);
  const std::string name_;
  P param1_;
  Q param2_;
};
 
template <class T, class P, class Q>
Demon* MakeDelayedConstraintDemon2(Solver* const s, T* const ct,
                                   void (T::*method)(P, Q),
                                   const std::string& name, P param1,
                                   Q param2) {
  return s->RevAlloc(
      new DelayedCallMethod2<T, P, Q>(ct, method, name, param1, param2));
}
 
#endif  // !defined(SWIG)
 
// TODO(user): rename Start to Synchronize ?
// TODO(user): decouple the iterating from the defining of a neighbor.
class LocalSearchOperator : public BaseObject {
 public:
  LocalSearchOperator() {}
  ~LocalSearchOperator() override {}
  virtual bool MakeNextNeighbor(Assignment* delta, Assignment* deltadelta) = 0;
  virtual void Start(const Assignment* assignment) = 0;
  virtual void Reset() {}
#ifndef SWIG
  virtual const LocalSearchOperator* Self() const { return this; }
#endif  // SWIG
  virtual bool HasFragments() const { return false; }
  virtual bool HoldsDelta() const { return false; }
};
 
template <class V, class Val, class Handler>
class VarLocalSearchOperator : public LocalSearchOperator {
 public:
  VarLocalSearchOperator() : activated_(), was_activated_(), cleared_(true) {}
  VarLocalSearchOperator(std::vector<V*> vars, Handler var_handler)
      : activated_(),
        was_activated_(),
        cleared_(true),
        var_handler_(var_handler) {}
  ~VarLocalSearchOperator() override {}
  bool HoldsDelta() const override { return true; }
  void Start(const Assignment* assignment) override {
    const int size = Size();
    CHECK_LE(size, assignment->Size())
        << "Assignment contains fewer variables than operator";
    for (int i = 0; i < size; ++i) {
      activated_.Set(i, var_handler_.ValueFromAssignent(*assignment, vars_[i],
                                                        i, &values_[i]));
    }
    prev_values_ = old_values_;
    old_values_ = values_;
    was_activated_.SetContentFromBitsetOfSameSize(activated_);
    OnStart();
  }
  virtual bool IsIncremental() const { return false; }
  int Size() const { return vars_.size(); }
  const Val& Value(int64 index) const {
    DCHECK_LT(index, vars_.size());
    return values_[index];
  }
  V* Var(int64 index) const { return vars_[index]; }
  virtual bool SkipUnchanged(int index) const { return false; }
  const Val& OldValue(int64 index) const { return old_values_[index]; }
  void SetValue(int64 index, const Val& value) {
    values_[index] = value;
    MarkChange(index);
  }
  bool Activated(int64 index) const { return activated_[index]; }
  void Activate(int64 index) {
    activated_.Set(index);
    MarkChange(index);
  }
  void Deactivate(int64 index) {
    activated_.Clear(index);
    MarkChange(index);
  }
  bool ApplyChanges(Assignment* delta, Assignment* deltadelta) const {
    if (IsIncremental() && !cleared_) {
      for (const int64 index : delta_changes_.PositionsSetAtLeastOnce()) {
        V* var = Var(index);
        const Val& value = Value(index);
        const bool activated = activated_[index];
        var_handler_.AddToAssignment(var, value, activated, nullptr, index,
                                     deltadelta);
        var_handler_.AddToAssignment(var, value, activated,
                                     &assignment_indices_, index, delta);
      }
    } else {
      delta->Clear();
      for (const int64 index : changes_.PositionsSetAtLeastOnce()) {
        const Val& value = Value(index);
        const bool activated = activated_[index];
        if (!activated || value != OldValue(index) || !SkipUnchanged(index)) {
          var_handler_.AddToAssignment(Var(index), value, activated_[index],
                                       &assignment_indices_, index, delta);
        }
      }
    }
    return true;
  }
  void RevertChanges(bool incremental) {
    cleared_ = false;
    delta_changes_.SparseClearAll();
    if (incremental && IsIncremental()) return;
    cleared_ = true;
    for (const int64 index : changes_.PositionsSetAtLeastOnce()) {
      values_[index] = old_values_[index];
      var_handler_.OnRevertChanges(index);
      activated_.CopyBucket(was_activated_, index);
      assignment_indices_[index] = -1;
    }
    changes_.SparseClearAll();
  }
  void AddVars(const std::vector<V*>& vars) {
    if (!vars.empty()) {
      vars_.insert(vars_.end(), vars.begin(), vars.end());
      const int64 size = Size();
      values_.resize(size);
      old_values_.resize(size);
      prev_values_.resize(size);
      assignment_indices_.resize(size, -1);
      activated_.Resize(size);
      was_activated_.Resize(size);
      changes_.ClearAndResize(size);
      delta_changes_.ClearAndResize(size);
      var_handler_.OnAddVars();
    }
  }
 
  virtual void OnStart() {}
 
 protected:
  void MarkChange(int64 index) {
    delta_changes_.Set(index);
    changes_.Set(index);
  }
 
  std::vector<V*> vars_;
  std::vector<Val> values_;
  std::vector<Val> old_values_;
  std::vector<Val> prev_values_;
  mutable std::vector<int> assignment_indices_;
  Bitset64<> activated_;
  Bitset64<> was_activated_;
  SparseBitset<> changes_;
  SparseBitset<> delta_changes_;
  bool cleared_;
  Handler var_handler_;
};
 
class IntVarLocalSearchHandler {
 public:
  void AddToAssignment(IntVar* var, int64 value, bool active,
                       std::vector<int>* assignment_indices, int64 index,
                       Assignment* assignment) const {
    Assignment::IntContainer* const container =
        assignment->MutableIntVarContainer();
    IntVarElement* element = nullptr;
    if (assignment_indices != nullptr) {
      if ((*assignment_indices)[index] == -1) {
        (*assignment_indices)[index] = container->Size();
        element = assignment->FastAdd(var);
      } else {
        element = container->MutableElement((*assignment_indices)[index]);
      }
    } else {
      element = assignment->FastAdd(var);
    }
    if (active) {
      element->SetValue(value);
      element->Activate();
    } else {
      element->Deactivate();
    }
  }
  bool ValueFromAssignent(const Assignment& assignment, IntVar* var,
                          int64 index, int64* value) {
    const Assignment::IntContainer& container = assignment.IntVarContainer();
    const IntVarElement* element = &(container.Element(index));
    if (element->Var() != var) {
      CHECK(container.Contains(var))
          << "Assignment does not contain operator variable " << var;
      element = &(container.Element(var));
    }
    *value = element->Value();
    return element->Activated();
  }
  void OnRevertChanges(int64 index) {}
  void OnAddVars() {}
};
 
 
#ifdef SWIG
// TODO(user): find a way to move this code back to the .i file, where it
#if defined(SWIGPYTHON)
%unignore VarLocalSearchOperator<IntVar, int64,
                                 IntVarLocalSearchHandler>::Size;
%unignore VarLocalSearchOperator<IntVar, int64,
                                 IntVarLocalSearchHandler>::Value;
%unignore VarLocalSearchOperator<IntVar, int64,
                                 IntVarLocalSearchHandler>::OldValue;
%unignore VarLocalSearchOperator<IntVar, int64,
                                 IntVarLocalSearchHandler>::SetValue;
%feature("director") VarLocalSearchOperator<IntVar, int64,
                                 IntVarLocalSearchHandler>::IsIncremental;
%feature("director") VarLocalSearchOperator<IntVar, int64,
                                 IntVarLocalSearchHandler>::OnStart;
%unignore VarLocalSearchOperator<IntVar, int64,
                                 IntVarLocalSearchHandler>::IsIncremental;
%unignore VarLocalSearchOperator<IntVar, int64,
                                 IntVarLocalSearchHandler>::OnStart;
#endif  // SWIGPYTHON
 
// clang-format off
%rename(IntVarLocalSearchOperatorTemplate)
        VarLocalSearchOperator<IntVar, int64, IntVarLocalSearchHandler>;
%template(IntVarLocalSearchOperatorTemplate)
        VarLocalSearchOperator<IntVar, int64, IntVarLocalSearchHandler>;
// clang-format on
#endif  // SWIG
 
class IntVarLocalSearchOperator
    : public VarLocalSearchOperator<IntVar, int64, IntVarLocalSearchHandler> {
 public:
  IntVarLocalSearchOperator() {}
  explicit IntVarLocalSearchOperator(const std::vector<IntVar*>& vars)
      : VarLocalSearchOperator<IntVar, int64, IntVarLocalSearchHandler>(
            vars, IntVarLocalSearchHandler()) {
    AddVars(vars);
  }
  ~IntVarLocalSearchOperator() override {}
  bool MakeNextNeighbor(Assignment* delta, Assignment* deltadelta) override;
 
 protected:
  // TODO(user): make it pure virtual, implies porting all apps overriding
  virtual bool MakeOneNeighbor();
};
 
class SequenceVarLocalSearchOperator;
 
class SequenceVarLocalSearchHandler {
 public:
  SequenceVarLocalSearchHandler() : op_(nullptr) {}
  SequenceVarLocalSearchHandler(const SequenceVarLocalSearchHandler& other)
      : op_(other.op_) {}
  explicit SequenceVarLocalSearchHandler(SequenceVarLocalSearchOperator* op)
      : op_(op) {}
  void AddToAssignment(SequenceVar* var, const std::vector<int>& value,
                       bool active, std::vector<int>* assignment_indices,
                       int64 index, Assignment* assignment) const;
  bool ValueFromAssignent(const Assignment& assignment, SequenceVar* var,
                          int64 index, std::vector<int>* value);
  void OnRevertChanges(int64 index);
  void OnAddVars();
 
 private:
  SequenceVarLocalSearchOperator* const op_;
};
 
#ifdef SWIG
// TODO(user): find a way to move this code back to the .i file, where it
// clang-format off
%rename(SequenceVarLocalSearchOperatorTemplate) VarLocalSearchOperator<
    SequenceVar, std::vector<int>, SequenceVarLocalSearchHandler>;
%template(SequenceVarLocalSearchOperatorTemplate) VarLocalSearchOperator<
      SequenceVar, std::vector<int>, SequenceVarLocalSearchHandler>;
// clang-format on
#endif
 
typedef VarLocalSearchOperator<SequenceVar, std::vector<int>,
                               SequenceVarLocalSearchHandler>
    SequenceVarLocalSearchOperatorTemplate;
 
class SequenceVarLocalSearchOperator
    : public SequenceVarLocalSearchOperatorTemplate {
 public:
  SequenceVarLocalSearchOperator() {}
  explicit SequenceVarLocalSearchOperator(const std::vector<SequenceVar*>& vars)
      : SequenceVarLocalSearchOperatorTemplate(
            vars, SequenceVarLocalSearchHandler(this)) {
    AddVars(vars);
  }
  ~SequenceVarLocalSearchOperator() override {}
  const std::vector<int>& Sequence(int64 index) const { return Value(index); }
  const std::vector<int>& OldSequence(int64 index) const {
    return OldValue(index);
  }
  void SetForwardSequence(int64 index, const std::vector<int>& value) {
    SetValue(index, value);
  }
  void SetBackwardSequence(int64 index, const std::vector<int>& value) {
    backward_values_[index] = value;
    MarkChange(index);
  }
 
 protected:
  friend class SequenceVarLocalSearchHandler;
 
  std::vector<std::vector<int>> backward_values_;
};
 
inline void SequenceVarLocalSearchHandler::AddToAssignment(
    SequenceVar* var, const std::vector<int>& value, bool active,
    std::vector<int>* assignment_indices, int64 index,
    Assignment* assignment) const {
  Assignment::SequenceContainer* const container =
      assignment->MutableSequenceVarContainer();
  SequenceVarElement* element = nullptr;
  if (assignment_indices != nullptr) {
    if ((*assignment_indices)[index] == -1) {
      (*assignment_indices)[index] = container->Size();
      element = assignment->FastAdd(var);
    } else {
      element = container->MutableElement((*assignment_indices)[index]);
    }
  } else {
    element = assignment->FastAdd(var);
  }
  if (active) {
    element->SetForwardSequence(value);
    element->SetBackwardSequence(op_->backward_values_[index]);
    element->Activate();
  } else {
    element->Deactivate();
  }
}
 
inline bool SequenceVarLocalSearchHandler::ValueFromAssignent(
    const Assignment& assignment, SequenceVar* var, int64 index,
    std::vector<int>* value) {
  const Assignment::SequenceContainer& container =
      assignment.SequenceVarContainer();
  const SequenceVarElement* element = &(container.Element(index));
  if (element->Var() != var) {
    CHECK(container.Contains(var))
        << "Assignment does not contain operator variable " << var;
    element = &(container.Element(var));
  }
  const std::vector<int>& element_value = element->ForwardSequence();
  CHECK_GE(var->size(), element_value.size());
  op_->backward_values_[index].clear();
  *value = element_value;
  return element->Activated();
}
 
inline void SequenceVarLocalSearchHandler::OnRevertChanges(int64 index) {
  op_->backward_values_[index].clear();
}
 
inline void SequenceVarLocalSearchHandler::OnAddVars() {
  op_->backward_values_.resize(op_->Size());
}
 
class BaseLns : public IntVarLocalSearchOperator {
 public:
  explicit BaseLns(const std::vector<IntVar*>& vars);
  ~BaseLns() override;
  virtual void InitFragments();
  virtual bool NextFragment() = 0;
  void AppendToFragment(int index);
  int FragmentSize() const;
  bool HasFragments() const override { return true; }
 
 protected:
  bool MakeOneNeighbor() override;
 
 private:
  void OnStart() override;
  std::vector<int> fragment_;
};
 
class ChangeValue : public IntVarLocalSearchOperator {
 public:
  explicit ChangeValue(const std::vector<IntVar*>& vars);
  ~ChangeValue() override;
  virtual int64 ModifyValue(int64 index, int64 value) = 0;
 
 protected:
  bool MakeOneNeighbor() override;
 
 private:
  void OnStart() override;
 
  int index_;
};
 
class PathOperator : public IntVarLocalSearchOperator {
 public:
  PathOperator(const std::vector<IntVar*>& next_vars,
               const std::vector<IntVar*>& path_vars, int number_of_base_nodes,
               bool skip_locally_optimal_paths,
               std::function<int(int64)> start_empty_path_class);
  ~PathOperator() override {}
  virtual bool MakeNeighbor() = 0;
  void Reset() override;
 
  // TODO(user): Make the following methods protected.
  bool SkipUnchanged(int index) const override;
 
  int64 Next(int64 node) const {
    DCHECK(!IsPathEnd(node));
    return Value(node);
  }
 
  int64 Path(int64 node) const {
    return ignore_path_vars_ ? 0LL : Value(node + number_of_nexts_);
  }
 
  int number_of_nexts() const { return number_of_nexts_; }
 
 protected:
  bool MakeOneNeighbor() override;
 
  int64 BaseNode(int i) const { return base_nodes_[i]; }
  int64 StartNode(int i) const { return path_starts_[base_paths_[i]]; }
  const std::vector<int64>& path_starts() const { return path_starts_; }
  int PathClass(int i) const {
    return start_empty_path_class_ != nullptr
               ? start_empty_path_class_(StartNode(i))
               : StartNode(i);
  }
 
  // TODO(user): remove this when automatic detection of such cases in done.
  virtual bool RestartAtPathStartOnSynchronize() { return false; }
  // TODO(user): ideally this should be OnSamePath(int64 node1, int64 node2);
  virtual bool OnSamePathAsPreviousBase(int64 base_index) { return false; }
  virtual int64 GetBaseNodeRestartPosition(int base_index) {
    return StartNode(base_index);
  }
  virtual void SetNextBaseToIncrement(int64 base_index) {
    next_base_to_increment_ = base_index;
  }
 
  int64 OldNext(int64 node) const {
    DCHECK(!IsPathEnd(node));
    return OldValue(node);
  }
 
  int64 OldPath(int64 node) const {
    return ignore_path_vars_ ? 0LL : OldValue(node + number_of_nexts_);
  }
 
  bool MoveChain(int64 before_chain, int64 chain_end, int64 destination);
 
  bool ReverseChain(int64 before_chain, int64 after_chain, int64* chain_last);
 
  bool MakeActive(int64 node, int64 destination);
  bool MakeChainInactive(int64 before_chain, int64 chain_end);
 
  void SetNext(int64 from, int64 to, int64 path) {
    DCHECK_LT(from, number_of_nexts_);
    SetValue(from, to);
    if (!ignore_path_vars_) {
      DCHECK_LT(from + number_of_nexts_, Size());
      SetValue(from + number_of_nexts_, path);
    }
  }
 
  bool IsPathEnd(int64 node) const { return node >= number_of_nexts_; }
 
  bool IsInactive(int64 node) const {
    return !IsPathEnd(node) && inactives_[node];
  }
 
  virtual bool InitPosition() const { return false; }
  void ResetPosition() { just_started_ = true; }
 
  int AddAlternativeSet(const std::vector<int64>& alternative_set) {
    const int alternative = alternative_sets_.size();
    for (int64 node : alternative_set) {
      DCHECK_EQ(-1, alternative_index_[node]);
      alternative_index_[node] = alternative;
    }
    alternative_sets_.push_back(alternative_set);
    sibling_alternative_.push_back(-1);
    return alternative;
  }
#ifndef SWIG
  void AddPairAlternativeSets(
      const std::vector<std::pair<std::vector<int64>, std::vector<int64>>>&
          pair_alternative_sets) {
    for (const auto& pair_alternative_set : pair_alternative_sets) {
      const int alternative = AddAlternativeSet(pair_alternative_set.first);
      sibling_alternative_.back() = alternative + 1;
      AddAlternativeSet(pair_alternative_set.second);
    }
  }
#endif  // SWIG
  int64 GetActiveInAlternativeSet(int alternative_index) const {
    return alternative_index >= 0
               ? active_in_alternative_set_[alternative_index]
               : -1;
  }
  int64 GetActiveAlternativeNode(int node) const {
    return GetActiveInAlternativeSet(alternative_index_[node]);
  }
  int64 GetActiveAlternativeSibling(int node) const {
    if (node >= alternative_index_.size()) return -1;
    const int alternative = alternative_index_[node];
    const int sibling_alternative =
        alternative >= 0 ? sibling_alternative_[alternative] : -1;
    return GetActiveInAlternativeSet(sibling_alternative);
  }
 
  const int number_of_nexts_;
  const bool ignore_path_vars_;
  int next_base_to_increment_;
  int num_paths_ = 0;
  std::vector<int64> start_to_path_;
 
 private:
  void OnStart() override;
  virtual void OnNodeInitialization() {}
  bool OnSamePath(int64 node1, int64 node2) const;
 
  bool CheckEnds() const {
    const int base_node_size = base_nodes_.size();
    for (int i = base_node_size - 1; i >= 0; --i) {
      if (base_nodes_[i] != end_nodes_[i]) {
        return true;
      }
    }
    return false;
  }
  bool IncrementPosition();
  void InitializePathStarts();
  void InitializeInactives();
  void InitializeBaseNodes();
  void InitializeAlternatives();
  bool CheckChainValidity(int64 before_chain, int64 chain_end,
                          int64 exclude) const;
  void Synchronize();
 
  std::vector<int> base_nodes_;
  std::vector<int> end_nodes_;
  std::vector<int> base_paths_;
  std::vector<int64> path_starts_;
  std::vector<bool> inactives_;
  bool just_started_;
  bool first_start_;
  std::function<int(int64)> start_empty_path_class_;
  bool skip_locally_optimal_paths_;
  bool optimal_paths_enabled_;
  std::vector<int> path_basis_;
  std::vector<bool> optimal_paths_;
#ifndef SWIG
  std::vector<std::vector<int64>> alternative_sets_;
#endif  // SWIG
  std::vector<int> alternative_index_;
  std::vector<int64> active_in_alternative_set_;
  std::vector<int> sibling_alternative_;
};
 
class PathWithPreviousNodesOperator : public PathOperator {
 public:
  PathWithPreviousNodesOperator(
      const std::vector<IntVar*>& vars,
      const std::vector<IntVar*>& secondary_vars, int number_of_base_nodes,
      std::function<int(int64)> start_empty_path_class);
  ~PathWithPreviousNodesOperator() override {}
 
  bool IsPathStart(int64 node) const { return prevs_[node] == -1; }
 
  int64 Prev(int64 node) const {
    DCHECK(!IsPathStart(node));
    return prevs_[node];
  }
 
  std::string DebugString() const override {
    return "PathWithPreviousNodesOperator";
  }
 
 protected:
  void OnNodeInitialization() override;  
 
 private:
  std::vector<int64> prevs_;
};
 
template <class T>
LocalSearchOperator* MakeLocalSearchOperator(
    Solver* solver, const std::vector<IntVar*>& vars,
    const std::vector<IntVar*>& secondary_vars,
    std::function<int(int64)> start_empty_path_class);
 
class TwoOpt;
class Relocate;
class Exchange;
class Cross;
class MakeActiveOperator;
class MakeInactiveOperator;
class MakeChainInactiveOperator;
class SwapActiveOperator;
class ExtendedSwapActiveOperator;
class MakeActiveAndRelocate;
class RelocateAndMakeActiveOperator;
class RelocateAndMakeInactiveOperator;
 
#if !defined(SWIG)
// A LocalSearchState is a container for variables with bounds that can be
// relaxed and tightened, saved and restored. It represents the solution state
// of a local search engine, and allows it to go from solution to solution by
// relaxing some variables to form a new subproblem, then tightening those
// variables to move to a new solution representation. That state may be saved
// to an internal copy, or reverted to the last saved internal copy.
// Relaxing a variable returns its bounds to their initial state.
// Tightening a variable's bounds may make its min larger than its max,
// in that case, the tightening function will return false, and the state will
// be marked as invalid. No other operations than Revert() can be called on an
// invalid state: in particular, an invalid state cannot be saved.
class LocalSearchVariable;
class LocalSearchState {
 public:
  LocalSearchVariable AddVariable(int64 initial_min, int64 initial_max);
  void Commit();
  void Revert();
  bool StateIsValid() const { return state_is_valid_; }
 
 private:
  friend class LocalSearchVariable;
 
  struct Bounds {
    int64 min;
    int64 max;
  };
 
  void RelaxVariableBounds(int variable_index);
  bool TightenVariableMin(int variable_index, int64 value);
  bool TightenVariableMax(int variable_index, int64 value);
  int64 VariableMin(int variable_index) const;
  int64 VariableMax(int variable_index) const;
 
  std::vector<Bounds> initial_variable_bounds_;
  std::vector<Bounds> variable_bounds_;
  std::vector<std::pair<Bounds, int>> saved_variable_bounds_trail_;
  std::vector<bool> variable_is_relaxed_;
  bool state_is_valid_ = true;
};
 
// A LocalSearchVariable can only be created by a LocalSearchState, then it is
// meant to be passed by copy. If at some point the duplication of
// LocalSearchState pointers is too expensive, we could switch to index only,
// and the user would have to know the relevant state. The present setup allows
// to ensure that variable users will not misuse the state.
class LocalSearchVariable {
 public:
  int64 Min() const { return state_->VariableMin(variable_index_); }
  int64 Max() const { return state_->VariableMax(variable_index_); }
  bool SetMin(int64 new_min) {
    return state_->TightenVariableMin(variable_index_, new_min);
  }
  bool SetMax(int64 new_max) {
    return state_->TightenVariableMax(variable_index_, new_max);
  }
  void Relax() { state_->RelaxVariableBounds(variable_index_); }
 
 private:
  // Only LocalSearchState can construct LocalSearchVariables.
  friend class LocalSearchState;
 
  LocalSearchVariable(LocalSearchState* state, int variable_index)
      : state_(state), variable_index_(variable_index) {}
 
  LocalSearchState* const state_;
  const int variable_index_;
};
#endif  // !defined(SWIG)
 
class LocalSearchFilter : public BaseObject {
 public:
  virtual void Relax(const Assignment* delta, const Assignment* deltadelta) {}
 
  virtual bool Accept(const Assignment* delta, const Assignment* deltadelta,
                      int64 objective_min, int64 objective_max) = 0;
  virtual bool IsIncremental() const { return false; }
 
  virtual void Synchronize(const Assignment* assignment,
                           const Assignment* delta) = 0;
  virtual void Revert() {}
 
  virtual int64 GetSynchronizedObjectiveValue() const { return 0LL; }
  // If the last Accept() call returned false, returns an undefined value.
  virtual int64 GetAcceptedObjectiveValue() const { return 0LL; }
};
 
#if !defined(SWIG)
class LocalSearchFilterManager : public LocalSearchFilter {
 public:
  LocalSearchFilterManager(Solver* const solver,
                           const std::vector<LocalSearchFilter*>& filters);
  std::string DebugString() const override {
    return "LocalSearchFilterManager";
  }
  void Relax(const Assignment* delta, const Assignment* deltadelta) override;
  void Revert() override;
  bool Accept(const Assignment* delta, const Assignment* deltadelta,
              int64 objective_min, int64 objective_max) override;
  void Synchronize(const Assignment* assignment,
                   const Assignment* delta) override;
  bool IsIncremental() const override { return is_incremental_; }
  int64 GetSynchronizedObjectiveValue() const override {
    return synchronized_value_;
  }
  int64 GetAcceptedObjectiveValue() const override { return accepted_value_; }
 
 private:
  Solver* const solver_;
  std::vector<LocalSearchFilter*> filters_;
  bool is_incremental_;
  int64 synchronized_value_;
  int64 accepted_value_;
};
#endif
 
class IntVarLocalSearchFilter : public LocalSearchFilter {
 public:
  explicit IntVarLocalSearchFilter(const std::vector<IntVar*>& vars);
  ~IntVarLocalSearchFilter() override;
  void Synchronize(const Assignment* assignment,
                   const Assignment* delta) override;
 
  bool FindIndex(IntVar* const var, int64* index) const {
    DCHECK(index != nullptr);
    const int var_index = var->index();
    *index = (var_index < var_index_to_index_.size())
                 ? var_index_to_index_[var_index]
                 : kUnassigned;
    return *index != kUnassigned;
  }
 
  void AddVars(const std::vector<IntVar*>& vars);
  int Size() const { return vars_.size(); }
  IntVar* Var(int index) const { return vars_[index]; }
  int64 Value(int index) const {
    DCHECK(IsVarSynced(index));
    return values_[index];
  }
  bool IsVarSynced(int index) const { return var_synced_[index]; }
 
 protected:
  virtual void OnSynchronize(const Assignment* delta) {}
  void SynchronizeOnAssignment(const Assignment* assignment);
 
 private:
  std::vector<IntVar*> vars_;
  std::vector<int64> values_;
  std::vector<bool> var_synced_;
  std::vector<int> var_index_to_index_;
  static const int kUnassigned;
};
 
class PropagationMonitor : public SearchMonitor {
 public:
  explicit PropagationMonitor(Solver* const solver);
  ~PropagationMonitor() override;
  std::string DebugString() const override { return "PropagationMonitor"; }
 
  virtual void BeginConstraintInitialPropagation(
      Constraint* const constraint) = 0;
  virtual void EndConstraintInitialPropagation(
      Constraint* const constraint) = 0;
  virtual void BeginNestedConstraintInitialPropagation(
      Constraint* const parent, Constraint* const nested) = 0;
  virtual void EndNestedConstraintInitialPropagation(
      Constraint* const parent, Constraint* const nested) = 0;
  virtual void RegisterDemon(Demon* const demon) = 0;
  virtual void BeginDemonRun(Demon* const demon) = 0;
  virtual void EndDemonRun(Demon* const demon) = 0;
  virtual void StartProcessingIntegerVariable(IntVar* const var) = 0;
  virtual void EndProcessingIntegerVariable(IntVar* const var) = 0;
  virtual void PushContext(const std::string& context) = 0;
  virtual void PopContext() = 0;
  virtual void SetMin(IntExpr* const expr, int64 new_min) = 0;
  virtual void SetMax(IntExpr* const expr, int64 new_max) = 0;
  virtual void SetRange(IntExpr* const expr, int64 new_min, int64 new_max) = 0;
  virtual void SetMin(IntVar* const var, int64 new_min) = 0;
  virtual void SetMax(IntVar* const var, int64 new_max) = 0;
  virtual void SetRange(IntVar* const var, int64 new_min, int64 new_max) = 0;
  virtual void RemoveValue(IntVar* const var, int64 value) = 0;
  virtual void SetValue(IntVar* const var, int64 value) = 0;
  virtual void RemoveInterval(IntVar* const var, int64 imin, int64 imax) = 0;
  virtual void SetValues(IntVar* const var,
                         const std::vector<int64>& values) = 0;
  virtual void RemoveValues(IntVar* const var,
                            const std::vector<int64>& values) = 0;
  virtual void SetStartMin(IntervalVar* const var, int64 new_min) = 0;
  virtual void SetStartMax(IntervalVar* const var, int64 new_max) = 0;
  virtual void SetStartRange(IntervalVar* const var, int64 new_min,
                             int64 new_max) = 0;
  virtual void SetEndMin(IntervalVar* const var, int64 new_min) = 0;
  virtual void SetEndMax(IntervalVar* const var, int64 new_max) = 0;
  virtual void SetEndRange(IntervalVar* const var, int64 new_min,
                           int64 new_max) = 0;
  virtual void SetDurationMin(IntervalVar* const var, int64 new_min) = 0;
  virtual void SetDurationMax(IntervalVar* const var, int64 new_max) = 0;
  virtual void SetDurationRange(IntervalVar* const var, int64 new_min,
                                int64 new_max) = 0;
  virtual void SetPerformed(IntervalVar* const var, bool value) = 0;
  virtual void RankFirst(SequenceVar* const var, int index) = 0;
  virtual void RankNotFirst(SequenceVar* const var, int index) = 0;
  virtual void RankLast(SequenceVar* const var, int index) = 0;
  virtual void RankNotLast(SequenceVar* const var, int index) = 0;
  virtual void RankSequence(SequenceVar* const var,
                            const std::vector<int>& rank_first,
                            const std::vector<int>& rank_last,
                            const std::vector<int>& unperformed) = 0;
  void Install() override;
};
 
class LocalSearchMonitor : public SearchMonitor {
  // TODO(user): Add monitoring of local search filters.
 public:
  explicit LocalSearchMonitor(Solver* const solver);
  ~LocalSearchMonitor() override;
  std::string DebugString() const override { return "LocalSearchMonitor"; }
 
  virtual void BeginOperatorStart() = 0;
  virtual void EndOperatorStart() = 0;
  virtual void BeginMakeNextNeighbor(const LocalSearchOperator* op) = 0;
  virtual void EndMakeNextNeighbor(const LocalSearchOperator* op,
                                   bool neighbor_found, const Assignment* delta,
                                   const Assignment* deltadelta) = 0;
  virtual void BeginFilterNeighbor(const LocalSearchOperator* op) = 0;
  virtual void EndFilterNeighbor(const LocalSearchOperator* op,
                                 bool neighbor_found) = 0;
  virtual void BeginAcceptNeighbor(const LocalSearchOperator* op) = 0;
  virtual void EndAcceptNeighbor(const LocalSearchOperator* op,
                                 bool neighbor_found) = 0;
  virtual void BeginFiltering(const LocalSearchFilter* filter) = 0;
  virtual void EndFiltering(const LocalSearchFilter* filter, bool reject) = 0;
 
  void Install() override;
};
 
class BooleanVar : public IntVar {
 public:
  static const int kUnboundBooleanVarValue;
 
  explicit BooleanVar(Solver* const s, const std::string& name = "")
      : IntVar(s, name), value_(kUnboundBooleanVarValue) {}
 
  ~BooleanVar() override {}
 
  int64 Min() const override { return (value_ == 1); }
  void SetMin(int64 m) override;
  int64 Max() const override { return (value_ != 0); }
  void SetMax(int64 m) override;
  void SetRange(int64 mi, int64 ma) override;
  bool Bound() const override { return (value_ != kUnboundBooleanVarValue); }
  int64 Value() const override {
    CHECK_NE(value_, kUnboundBooleanVarValue) << "variable is not bound";
    return value_;
  }
  void RemoveValue(int64 v) override;
  void RemoveInterval(int64 l, int64 u) override;
  void WhenBound(Demon* d) override;
  void WhenRange(Demon* d) override { WhenBound(d); }
  void WhenDomain(Demon* d) override { WhenBound(d); }
  uint64 Size() const override;
  bool Contains(int64 v) const override;
  IntVarIterator* MakeHoleIterator(bool reversible) const override;
  IntVarIterator* MakeDomainIterator(bool reversible) const override;
  std::string DebugString() const override;
  int VarType() const override { return BOOLEAN_VAR; }
 
  IntVar* IsEqual(int64 constant) override;
  IntVar* IsDifferent(int64 constant) override;
  IntVar* IsGreaterOrEqual(int64 constant) override;
  IntVar* IsLessOrEqual(int64 constant) override;
 
  virtual void RestoreValue() = 0;
  std::string BaseName() const override { return "BooleanVar"; }
 
  int RawValue() const { return value_; }
 
 protected:
  int value_;
  SimpleRevFIFO<Demon*> bound_demons_;
  SimpleRevFIFO<Demon*> delayed_bound_demons_;
};
 
class SymmetryManager;
 
class SymmetryBreaker : public DecisionVisitor {
 public:
  SymmetryBreaker()
      : symmetry_manager_(nullptr), index_in_symmetry_manager_(-1) {}
  ~SymmetryBreaker() override {}
 
  void AddIntegerVariableEqualValueClause(IntVar* const var, int64 value);
  void AddIntegerVariableGreaterOrEqualValueClause(IntVar* const var,
                                                   int64 value);
  void AddIntegerVariableLessOrEqualValueClause(IntVar* const var, int64 value);
 
 private:
  friend class SymmetryManager;
  void set_symmetry_manager_and_index(SymmetryManager* manager, int index) {
    CHECK(symmetry_manager_ == nullptr);
    CHECK_EQ(-1, index_in_symmetry_manager_);
    symmetry_manager_ = manager;
    index_in_symmetry_manager_ = index;
  }
  SymmetryManager* symmetry_manager() const { return symmetry_manager_; }
  int index_in_symmetry_manager() const { return index_in_symmetry_manager_; }
 
  SymmetryManager* symmetry_manager_;
  int index_in_symmetry_manager_;
};
 
class SearchLog : public SearchMonitor {
 public:
  SearchLog(Solver* const s, OptimizeVar* const obj, IntVar* const var,
            double scaling_factor, double offset,
            std::function<std::string()> display_callback, int period);
  ~SearchLog() override;
  void EnterSearch() override;
  void ExitSearch() override;
  bool AtSolution() override;
  void BeginFail() override;
  void NoMoreSolutions() override;
  void AcceptUncheckedNeighbor() override;
  void ApplyDecision(Decision* const decision) override;
  void RefuteDecision(Decision* const decision) override;
  void OutputDecision();
  void Maintain();
  void BeginInitialPropagation() override;
  void EndInitialPropagation() override;
  std::string DebugString() const override;
 
 protected:
  /* Bottleneck function used for all UI related output. */
  virtual void OutputLine(const std::string& line);
 
 private:
  static std::string MemoryUsage();
 
  const int period_;
  std::unique_ptr<WallTimer> timer_;
  IntVar* const var_;
  OptimizeVar* const obj_;
  const double scaling_factor_;
  const double offset_;
  std::function<std::string()> display_callback_;
  int nsol_;
  int64 tick_;
  int64 objective_min_;
  int64 objective_max_;
  int min_right_depth_;
  int max_depth_;
  int sliding_min_depth_;
  int sliding_max_depth_;
};
 
class ModelCache {
 public:
  enum VoidConstraintType {
    VOID_FALSE_CONSTRAINT = 0,
    VOID_TRUE_CONSTRAINT,
    VOID_CONSTRAINT_MAX,
  };
 
  enum VarConstantConstraintType {
    VAR_CONSTANT_EQUALITY = 0,
    VAR_CONSTANT_GREATER_OR_EQUAL,
    VAR_CONSTANT_LESS_OR_EQUAL,
    VAR_CONSTANT_NON_EQUALITY,
    VAR_CONSTANT_CONSTRAINT_MAX,
  };
 
  enum VarConstantConstantConstraintType {
    VAR_CONSTANT_CONSTANT_BETWEEN = 0,
    VAR_CONSTANT_CONSTANT_CONSTRAINT_MAX,
  };
 
  enum ExprExprConstraintType {
    EXPR_EXPR_EQUALITY = 0,
    EXPR_EXPR_GREATER,
    EXPR_EXPR_GREATER_OR_EQUAL,
    EXPR_EXPR_LESS,
    EXPR_EXPR_LESS_OR_EQUAL,
    EXPR_EXPR_NON_EQUALITY,
    EXPR_EXPR_CONSTRAINT_MAX,
  };
 
  enum ExprExpressionType {
    EXPR_OPPOSITE = 0,
    EXPR_ABS,
    EXPR_SQUARE,
    EXPR_EXPRESSION_MAX,
  };
 
  enum ExprExprExpressionType {
    EXPR_EXPR_DIFFERENCE = 0,
    EXPR_EXPR_PROD,
    EXPR_EXPR_DIV,
    EXPR_EXPR_MAX,
    EXPR_EXPR_MIN,
    EXPR_EXPR_SUM,
    EXPR_EXPR_IS_LESS,
    EXPR_EXPR_IS_LESS_OR_EQUAL,
    EXPR_EXPR_IS_EQUAL,
    EXPR_EXPR_IS_NOT_EQUAL,
    EXPR_EXPR_EXPRESSION_MAX,
  };
 
  enum ExprExprConstantExpressionType {
    EXPR_EXPR_CONSTANT_CONDITIONAL = 0,
    EXPR_EXPR_CONSTANT_EXPRESSION_MAX,
  };
 
  enum ExprConstantExpressionType {
    EXPR_CONSTANT_DIFFERENCE = 0,
    EXPR_CONSTANT_DIVIDE,
    EXPR_CONSTANT_PROD,
    EXPR_CONSTANT_MAX,
    EXPR_CONSTANT_MIN,
    EXPR_CONSTANT_SUM,
    EXPR_CONSTANT_IS_EQUAL,
    EXPR_CONSTANT_IS_NOT_EQUAL,
    EXPR_CONSTANT_IS_GREATER_OR_EQUAL,
    EXPR_CONSTANT_IS_LESS_OR_EQUAL,
    EXPR_CONSTANT_EXPRESSION_MAX,
  };
  enum VarConstantConstantExpressionType {
    VAR_CONSTANT_CONSTANT_SEMI_CONTINUOUS = 0,
    VAR_CONSTANT_CONSTANT_EXPRESSION_MAX,
  };
 
  enum VarConstantArrayExpressionType {
    VAR_CONSTANT_ARRAY_ELEMENT = 0,
    VAR_CONSTANT_ARRAY_EXPRESSION_MAX,
  };
 
  enum VarArrayConstantArrayExpressionType {
    VAR_ARRAY_CONSTANT_ARRAY_SCAL_PROD = 0,
    VAR_ARRAY_CONSTANT_ARRAY_EXPRESSION_MAX,
  };
 
  enum VarArrayExpressionType {
    VAR_ARRAY_MAX = 0,
    VAR_ARRAY_MIN,
    VAR_ARRAY_SUM,
    VAR_ARRAY_EXPRESSION_MAX,
  };
 
  enum VarArrayConstantExpressionType {
    VAR_ARRAY_CONSTANT_INDEX = 0,
    VAR_ARRAY_CONSTANT_EXPRESSION_MAX,
  };
 
  explicit ModelCache(Solver* const solver);
  virtual ~ModelCache();
 
  virtual void Clear() = 0;
 
 
  virtual Constraint* FindVoidConstraint(VoidConstraintType type) const = 0;
 
  virtual void InsertVoidConstraint(Constraint* const ct,
                                    VoidConstraintType type) = 0;
 
  virtual Constraint* FindVarConstantConstraint(
      IntVar* const var, int64 value, VarConstantConstraintType type) const = 0;
 
  virtual void InsertVarConstantConstraint(Constraint* const ct,
                                           IntVar* const var, int64 value,
                                           VarConstantConstraintType type) = 0;
 
 
  virtual Constraint* FindVarConstantConstantConstraint(
      IntVar* const var, int64 value1, int64 value2,
      VarConstantConstantConstraintType type) const = 0;
 
  virtual void InsertVarConstantConstantConstraint(
      Constraint* const ct, IntVar* const var, int64 value1, int64 value2,
      VarConstantConstantConstraintType type) = 0;
 
 
  virtual Constraint* FindExprExprConstraint(
      IntExpr* const expr1, IntExpr* const expr2,
      ExprExprConstraintType type) const = 0;
 
  virtual void InsertExprExprConstraint(Constraint* const ct,
                                        IntExpr* const expr1,
                                        IntExpr* const expr2,
                                        ExprExprConstraintType type) = 0;
 
 
  virtual IntExpr* FindExprExpression(IntExpr* const expr,
                                      ExprExpressionType type) const = 0;
 
  virtual void InsertExprExpression(IntExpr* const expression,
                                    IntExpr* const expr,
                                    ExprExpressionType type) = 0;
 
 
  virtual IntExpr* FindExprConstantExpression(
      IntExpr* const expr, int64 value,
      ExprConstantExpressionType type) const = 0;
 
  virtual void InsertExprConstantExpression(
      IntExpr* const expression, IntExpr* const var, int64 value,
      ExprConstantExpressionType type) = 0;
 
 
  virtual IntExpr* FindExprExprExpression(
      IntExpr* const var1, IntExpr* const var2,
      ExprExprExpressionType type) const = 0;
 
  virtual void InsertExprExprExpression(IntExpr* const expression,
                                        IntExpr* const var1,
                                        IntExpr* const var2,
                                        ExprExprExpressionType type) = 0;
 
 
  virtual IntExpr* FindExprExprConstantExpression(
      IntExpr* const var1, IntExpr* const var2, int64 constant,
      ExprExprConstantExpressionType type) const = 0;
 
  virtual void InsertExprExprConstantExpression(
      IntExpr* const expression, IntExpr* const var1, IntExpr* const var2,
      int64 constant, ExprExprConstantExpressionType type) = 0;
 
 
  virtual IntExpr* FindVarConstantConstantExpression(
      IntVar* const var, int64 value1, int64 value2,
      VarConstantConstantExpressionType type) const = 0;
 
  virtual void InsertVarConstantConstantExpression(
      IntExpr* const expression, IntVar* const var, int64 value1, int64 value2,
      VarConstantConstantExpressionType type) = 0;
 
 
  virtual IntExpr* FindVarConstantArrayExpression(
      IntVar* const var, const std::vector<int64>& values,
      VarConstantArrayExpressionType type) const = 0;
 
  virtual void InsertVarConstantArrayExpression(
      IntExpr* const expression, IntVar* const var,
      const std::vector<int64>& values,
      VarConstantArrayExpressionType type) = 0;
 
 
  virtual IntExpr* FindVarArrayExpression(
      const std::vector<IntVar*>& vars, VarArrayExpressionType type) const = 0;
 
  virtual void InsertVarArrayExpression(IntExpr* const expression,
                                        const std::vector<IntVar*>& vars,
                                        VarArrayExpressionType type) = 0;
 
 
  virtual IntExpr* FindVarArrayConstantArrayExpression(
      const std::vector<IntVar*>& vars, const std::vector<int64>& values,
      VarArrayConstantArrayExpressionType type) const = 0;
 
  virtual void InsertVarArrayConstantArrayExpression(
      IntExpr* const expression, const std::vector<IntVar*>& var,
      const std::vector<int64>& values,
      VarArrayConstantArrayExpressionType type) = 0;
 
 
  virtual IntExpr* FindVarArrayConstantExpression(
      const std::vector<IntVar*>& vars, int64 value,
      VarArrayConstantExpressionType type) const = 0;
 
  virtual void InsertVarArrayConstantExpression(
      IntExpr* const expression, const std::vector<IntVar*>& var, int64 value,
      VarArrayConstantExpressionType type) = 0;
 
  Solver* solver() const;
 
 private:
  Solver* const solver_;
};
 
#if !defined(SWIG)
class ArgumentHolder {
 public:
  const std::string& TypeName() const;
  void SetTypeName(const std::string& type_name);
 
  void SetIntegerArgument(const std::string& arg_name, int64 value);
  void SetIntegerArrayArgument(const std::string& arg_name,
                               const std::vector<int64>& values);
  void SetIntegerMatrixArgument(const std::string& arg_name,
                                const IntTupleSet& values);
  void SetIntegerExpressionArgument(const std::string& arg_name,
                                    IntExpr* const expr);
  void SetIntegerVariableArrayArgument(const std::string& arg_name,
                                       const std::vector<IntVar*>& vars);
  void SetIntervalArgument(const std::string& arg_name, IntervalVar* const var);
  void SetIntervalArrayArgument(const std::string& arg_name,
                                const std::vector<IntervalVar*>& vars);
  void SetSequenceArgument(const std::string& arg_name, SequenceVar* const var);
  void SetSequenceArrayArgument(const std::string& arg_name,
                                const std::vector<SequenceVar*>& vars);
 
  bool HasIntegerExpressionArgument(const std::string& arg_name) const;
  bool HasIntegerVariableArrayArgument(const std::string& arg_name) const;
 
  int64 FindIntegerArgumentWithDefault(const std::string& arg_name,
                                       int64 def) const;
  int64 FindIntegerArgumentOrDie(const std::string& arg_name) const;
  const std::vector<int64>& FindIntegerArrayArgumentOrDie(
      const std::string& arg_name) const;
  const IntTupleSet& FindIntegerMatrixArgumentOrDie(
      const std::string& arg_name) const;
 
  IntExpr* FindIntegerExpressionArgumentOrDie(
      const std::string& arg_name) const;
  const std::vector<IntVar*>& FindIntegerVariableArrayArgumentOrDie(
      const std::string& arg_name) const;
 
 private:
  std::string type_name_;
  absl::flat_hash_map<std::string, int64> integer_argument_;
  absl::flat_hash_map<std::string, std::vector<int64>> integer_array_argument_;
  absl::flat_hash_map<std::string, IntTupleSet> matrix_argument_;
  absl::flat_hash_map<std::string, IntExpr*> integer_expression_argument_;
  absl::flat_hash_map<std::string, IntervalVar*> interval_argument_;
  absl::flat_hash_map<std::string, SequenceVar*> sequence_argument_;
  absl::flat_hash_map<std::string, std::vector<IntVar*>>
      integer_variable_array_argument_;
  absl::flat_hash_map<std::string, std::vector<IntervalVar*>>
      interval_array_argument_;
  absl::flat_hash_map<std::string, std::vector<SequenceVar*>>
      sequence_array_argument_;
};
 
class ModelParser : public ModelVisitor {
 public:
  ModelParser();
 
  ~ModelParser() override;
 
  void BeginVisitModel(const std::string& solver_name) override;
  void EndVisitModel(const std::string& solver_name) override;
  void BeginVisitConstraint(const std::string& type_name,
                            const Constraint* const constraint) override;
  void EndVisitConstraint(const std::string& type_name,
                          const Constraint* const constraint) override;
  void BeginVisitIntegerExpression(const std::string& type_name,
                                   const IntExpr* const expr) override;
  void EndVisitIntegerExpression(const std::string& type_name,
                                 const IntExpr* const expr) override;
  void VisitIntegerVariable(const IntVar* const variable,
                            IntExpr* const delegate) override;
  void VisitIntegerVariable(const IntVar* const variable,
                            const std::string& operation, int64 value,
                            IntVar* const delegate) override;
  void VisitIntervalVariable(const IntervalVar* const variable,
                             const std::string& operation, int64 value,
                             IntervalVar* const delegate) override;
  void VisitSequenceVariable(const SequenceVar* const variable) override;
  void VisitIntegerArgument(const std::string& arg_name, int64 value) override;
  void VisitIntegerArrayArgument(const std::string& arg_name,
                                 const std::vector<int64>& values) override;
  void VisitIntegerMatrixArgument(const std::string& arg_name,
                                  const IntTupleSet& values) override;
  void VisitIntegerExpressionArgument(const std::string& arg_name,
                                      IntExpr* const argument) override;
  void VisitIntegerVariableArrayArgument(
      const std::string& arg_name,
      const std::vector<IntVar*>& arguments) override;
  void VisitIntervalArgument(const std::string& arg_name,
                             IntervalVar* const argument) override;
  void VisitIntervalArrayArgument(
      const std::string& arg_name,
      const std::vector<IntervalVar*>& arguments) override;
  void VisitSequenceArgument(const std::string& arg_name,
                             SequenceVar* const argument) override;
  void VisitSequenceArrayArgument(
      const std::string& arg_name,
      const std::vector<SequenceVar*>& arguments) override;
 
 protected:
  void PushArgumentHolder();
  void PopArgumentHolder();
  ArgumentHolder* Top() const;
 
 private:
  std::vector<ArgumentHolder*> holders_;
};
 
template <class T>
class ArrayWithOffset : public BaseObject {
 public:
  ArrayWithOffset(int64 index_min, int64 index_max)
      : index_min_(index_min),
        index_max_(index_max),
        values_(new T[index_max - index_min + 1]) {
    DCHECK_LE(index_min, index_max);
  }
 
  ~ArrayWithOffset() override {}
 
  virtual T Evaluate(int64 index) const {
    DCHECK_GE(index, index_min_);
    DCHECK_LE(index, index_max_);
    return values_[index - index_min_];
  }
 
  void SetValue(int64 index, T value) {
    DCHECK_GE(index, index_min_);
    DCHECK_LE(index, index_max_);
    values_[index - index_min_] = value;
  }
 
  std::string DebugString() const override { return "ArrayWithOffset"; }
 
 private:
  const int64 index_min_;
  const int64 index_max_;
  std::unique_ptr<T[]> values_;
};
#endif  // SWIG
 
template <class T, class C>
class RevGrowingArray {
 public:
  explicit RevGrowingArray(int64 block_size)
      : block_size_(block_size), block_offset_(0) {
    CHECK_GT(block_size, 0);
  }
 
  ~RevGrowingArray() {
    for (int i = 0; i < elements_.size(); ++i) {
      delete[] elements_[i];
    }
  }
 
  T At(int64 index) const {
    const int64 block_index = ComputeBlockIndex(index);
    const int64 relative_index = block_index - block_offset_;
    if (relative_index < 0 || relative_index >= elements_.size()) {
      return T();
    }
    const T* block = elements_[relative_index];
    return block != nullptr ? block[index - block_index * block_size_] : T();
  }
 
  void RevInsert(Solver* const solver, int64 index, T value) {
    const int64 block_index = ComputeBlockIndex(index);
    T* const block = GetOrCreateBlock(block_index);
    const int64 residual = index - block_index * block_size_;
    solver->SaveAndSetValue(reinterpret_cast<C*>(&block[residual]),
                            reinterpret_cast<C>(value));
  }
 
 private:
  T* NewBlock() const {
    T* const result = new T[block_size_];
    for (int i = 0; i < block_size_; ++i) {
      result[i] = T();
    }
    return result;
  }
 
  T* GetOrCreateBlock(int block_index) {
    if (elements_.size() == 0) {
      block_offset_ = block_index;
      GrowUp(block_index);
    } else if (block_index < block_offset_) {
      GrowDown(block_index);
    } else if (block_index - block_offset_ >= elements_.size()) {
      GrowUp(block_index);
    }
    T* block = elements_[block_index - block_offset_];
    if (block == nullptr) {
      block = NewBlock();
      elements_[block_index - block_offset_] = block;
    }
    return block;
  }
 
  int64 ComputeBlockIndex(int64 value) const {
    return value >= 0 ? value / block_size_
                      : (value - block_size_ + 1) / block_size_;
  }
 
  void GrowUp(int64 block_index) {
    elements_.resize(block_index - block_offset_ + 1);
  }
 
  void GrowDown(int64 block_index) {
    const int64 delta = block_offset_ - block_index;
    block_offset_ = block_index;
    DCHECK_GT(delta, 0);
    elements_.insert(elements_.begin(), delta, nullptr);
  }
 
  const int64 block_size_;
  std::vector<T*> elements_;
  int block_offset_;
};
 
template <class T>
class RevIntSet {
 public:
  static const int kNoInserted = -1;
 
  explicit RevIntSet(int capacity)
      : elements_(new T[capacity]),
        num_elements_(0),
        capacity_(capacity),
        position_(new int[capacity]),
        delete_position_(true) {
    for (int i = 0; i < capacity; ++i) {
      position_[i] = kNoInserted;
    }
  }
 
  RevIntSet(int capacity, int* shared_positions, int shared_positions_size)
      : elements_(new T[capacity]),
        num_elements_(0),
        capacity_(capacity),
        position_(shared_positions),
        delete_position_(false) {
    for (int i = 0; i < shared_positions_size; ++i) {
      position_[i] = kNoInserted;
    }
  }
 
  ~RevIntSet() {
    if (delete_position_) {
      delete[] position_;
    }
  }
 
  int Size() const { return num_elements_.Value(); }
 
  int Capacity() const { return capacity_; }
 
  T Element(int i) const {
    DCHECK_GE(i, 0);
    DCHECK_LT(i, num_elements_.Value());
    return elements_[i];
  }
 
  T RemovedElement(int i) const {
    DCHECK_GE(i, 0);
    DCHECK_LT(i + num_elements_.Value(), capacity_);
    return elements_[i + num_elements_.Value()];
  }
 
  void Insert(Solver* const solver, const T& elt) {
    const int position = num_elements_.Value();
    DCHECK_LT(position, capacity_);  
    DCHECK(NotAlreadyInserted(elt));
    elements_[position] = elt;
    position_[elt] = position;
    num_elements_.Incr(solver);
  }
 
  void Remove(Solver* const solver, const T& value_index) {
    num_elements_.Decr(solver);
    SwapTo(value_index, num_elements_.Value());
  }
 
  void Restore(Solver* const solver, const T& value_index) {
    SwapTo(value_index, num_elements_.Value());
    num_elements_.Incr(solver);
  }
 
  void Clear(Solver* const solver) { num_elements_.SetValue(solver, 0); }
 
  typedef const T* const_iterator;
  const_iterator begin() const { return elements_.get(); }
  const_iterator end() const { return elements_.get() + num_elements_.Value(); }
 
 private:
  bool NotAlreadyInserted(const T& elt) {
    for (int i = 0; i < num_elements_.Value(); ++i) {
      if (elt == elements_[i]) {
        return false;
      }
    }
    return true;
  }
 
  void SwapTo(T value_index, int next_position) {
    const int current_position = position_[value_index];
    if (current_position != next_position) {
      const T next_value_index = elements_[next_position];
      elements_[current_position] = next_value_index;
      elements_[next_position] = value_index;
      position_[value_index] = next_position;
      position_[next_value_index] = current_position;
    }
  }
 
  std::unique_ptr<T[]> elements_;
  NumericalRev<int> num_elements_;
  const int capacity_;
  int* position_;
  const bool delete_position_;
};
 
 
class RevPartialSequence {
 public:
  explicit RevPartialSequence(const std::vector<int>& items)
      : elements_(items),
        first_ranked_(0),
        last_ranked_(items.size() - 1),
        size_(items.size()),
        position_(new int[size_]) {
    for (int i = 0; i < size_; ++i) {
      elements_[i] = items[i];
      position_[i] = i;
    }
  }
 
  explicit RevPartialSequence(int size)
      : elements_(size),
        first_ranked_(0),
        last_ranked_(size - 1),
        size_(size),
        position_(new int[size_]) {
    for (int i = 0; i < size_; ++i) {
      elements_[i] = i;
      position_[i] = i;
    }
  }
 
  ~RevPartialSequence() {}
 
  int NumFirstRanked() const { return first_ranked_.Value(); }
 
  int NumLastRanked() const { return size_ - 1 - last_ranked_.Value(); }
 
  int Size() const { return size_; }
 
#if !defined(SWIG)
  const int& operator[](int index) const {
    DCHECK_GE(index, 0);
    DCHECK_LT(index, size_);
    return elements_[index];
  }
#endif
 
  void RankFirst(Solver* const solver, int elt) {
    DCHECK_LE(first_ranked_.Value(), last_ranked_.Value());
    SwapTo(elt, first_ranked_.Value());
    first_ranked_.Incr(solver);
  }
 
  void RankLast(Solver* const solver, int elt) {
    DCHECK_LE(first_ranked_.Value(), last_ranked_.Value());
    SwapTo(elt, last_ranked_.Value());
    last_ranked_.Decr(solver);
  }
 
  bool IsRanked(int elt) const {
    const int position = position_[elt];
    return (position < first_ranked_.Value() ||
            position > last_ranked_.Value());
  }
 
  std::string DebugString() const {
    std::string result = "[";
    for (int i = 0; i < first_ranked_.Value(); ++i) {
      absl::StrAppend(&result, elements_[i]);
      if (i != first_ranked_.Value() - 1) {
        result.append("-");
      }
    }
    result.append("|");
    for (int i = first_ranked_.Value(); i <= last_ranked_.Value(); ++i) {
      absl::StrAppend(&result, elements_[i]);
      if (i != last_ranked_.Value()) {
        result.append("-");
      }
    }
    result.append("|");
    for (int i = last_ranked_.Value() + 1; i < size_; ++i) {
      absl::StrAppend(&result, elements_[i]);
      if (i != size_ - 1) {
        result.append("-");
      }
    }
    result.append("]");
    return result;
  }
 
 private:
  void SwapTo(int elt, int next_position) {
    const int current_position = position_[elt];
    if (current_position != next_position) {
      const int next_elt = elements_[next_position];
      elements_[current_position] = next_elt;
      elements_[next_position] = elt;
      position_[elt] = next_position;
      position_[next_elt] = current_position;
    }
  }
 
  std::vector<int> elements_;
  NumericalRev<int> first_ranked_;
  NumericalRev<int> last_ranked_;
  const int size_;
  std::unique_ptr<int[]> position_;
};
 
class UnsortedNullableRevBitset {
 public:
  explicit UnsortedNullableRevBitset(int bit_size);
 
  ~UnsortedNullableRevBitset() {}
 
  void Init(Solver* const solver, const std::vector<uint64>& mask);
 
  bool RevSubtract(Solver* const solver, const std::vector<uint64>& mask);
 
  bool RevAnd(Solver* const solver, const std::vector<uint64>& mask);
 
  int ActiveWordSize() const { return active_words_.Size(); }
 
  bool Empty() const { return active_words_.Size() == 0; }
 
  bool Intersects(const std::vector<uint64>& mask, int* support_index);
 
  int64 bit_size() const { return bit_size_; }
  int64 word_size() const { return word_size_; }
  const RevIntSet<int>& active_words() const { return active_words_; }
 
 private:
  void CleanUpActives(Solver* const solver);
 
  const int64 bit_size_;
  const int64 word_size_;
  RevArray<uint64> bits_;
  RevIntSet<int> active_words_;
  std::vector<int> to_remove_;
};
 
template <class T>
bool IsArrayConstant(const std::vector<T>& values, const T& value) {
  for (int i = 0; i < values.size(); ++i) {
    if (values[i] != value) {
      return false;
    }
  }
  return true;
}
 
template <class T>
bool IsArrayBoolean(const std::vector<T>& values) {
  for (int i = 0; i < values.size(); ++i) {
    if (values[i] != 0 && values[i] != 1) {
      return false;
    }
  }
  return true;
}
 
template <class T>
bool AreAllOnes(const std::vector<T>& values) {
  return IsArrayConstant(values, T(1));
}
 
template <class T>
bool AreAllNull(const std::vector<T>& values) {
  return IsArrayConstant(values, T(0));
}
 
template <class T>
bool AreAllGreaterOrEqual(const std::vector<T>& values, const T& value) {
  for (const T& current_value : values) {
    if (current_value < value) {
      return false;
    }
  }
  return true;
}
 
template <class T>
bool AreAllLessOrEqual(const std::vector<T>& values, const T& value) {
  for (const T& current_value : values) {
    if (current_value > value) {
      return false;
    }
  }
  return true;
}
 
template <class T>
bool AreAllPositive(const std::vector<T>& values) {
  return AreAllGreaterOrEqual(values, T(0));
}
 
template <class T>
bool AreAllNegative(const std::vector<T>& values) {
  return AreAllLessOrEqual(values, T(0));
}
 
template <class T>
bool AreAllStrictlyPositive(const std::vector<T>& values) {
  return AreAllGreaterOrEqual(values, T(1));
}
 
template <class T>
bool AreAllStrictlyNegative(const std::vector<T>& values) {
  return AreAllLessOrEqual(values, T(-1));
}
 
template <class T>
bool IsIncreasingContiguous(const std::vector<T>& values) {
  for (int i = 0; i < values.size() - 1; ++i) {
    if (values[i + 1] != values[i] + 1) {
      return false;
    }
  }
  return true;
}
 
template <class T>
bool IsIncreasing(const std::vector<T>& values) {
  for (int i = 0; i < values.size() - 1; ++i) {
    if (values[i + 1] < values[i]) {
      return false;
    }
  }
  return true;
}
 
template <class T>
bool IsArrayInRange(const std::vector<IntVar*>& vars, T range_min,
                    T range_max) {
  for (int i = 0; i < vars.size(); ++i) {
    if (vars[i]->Min() < range_min || vars[i]->Max() > range_max) {
      return false;
    }
  }
  return true;
}
 
inline bool AreAllBound(const std::vector<IntVar*>& vars) {
  for (int i = 0; i < vars.size(); ++i) {
    if (!vars[i]->Bound()) {
      return false;
    }
  }
  return true;
}
 
inline bool AreAllBooleans(const std::vector<IntVar*>& vars) {
  return IsArrayInRange(vars, 0, 1);
}
 
template <class T>
bool AreAllBoundOrNull(const std::vector<IntVar*>& vars,
                       const std::vector<T>& values) {
  for (int i = 0; i < vars.size(); ++i) {
    if (values[i] != 0 && !vars[i]->Bound()) {
      return false;
    }
  }
  return true;
}
 
inline bool AreAllBoundTo(const std::vector<IntVar*>& vars, int64 value) {
  for (int i = 0; i < vars.size(); ++i) {
    if (!vars[i]->Bound() || vars[i]->Min() != value) {
      return false;
    }
  }
  return true;
}
 
inline int64 MaxVarArray(const std::vector<IntVar*>& vars) {
  DCHECK(!vars.empty());
  int64 result = kint64min;
  for (int i = 0; i < vars.size(); ++i) {
    result = std::max<int64>(result, vars[i]->Max());
  }
  return result;
}
 
inline int64 MinVarArray(const std::vector<IntVar*>& vars) {
  DCHECK(!vars.empty());
  int64 result = kint64max;
  for (int i = 0; i < vars.size(); ++i) {
    result = std::min<int64>(result, vars[i]->Min());
  }
  return result;
}
 
inline void FillValues(const std::vector<IntVar*>& vars,
                       std::vector<int64>* const values) {
  values->clear();
  values->resize(vars.size());
  for (int i = 0; i < vars.size(); ++i) {
    (*values)[i] = vars[i]->Value();
  }
}
 
inline int64 PosIntDivUp(int64 e, int64 v) {
  DCHECK_GT(v, 0);
  if (e >= 0) {
    return e % v == 0 ? e / v : e / v + 1;
  } else {
    return e / v;
  }
}
 
inline int64 PosIntDivDown(int64 e, int64 v) {
  DCHECK_GT(v, 0);
  if (e >= 0) {
    return e / v;
  } else {
    return e % v == 0 ? e / v : e / v - 1;
  }
}
 
std::vector<int64> ToInt64Vector(const std::vector<int>& input);
}  // namespace operations_research
 
#endif  // OR_TOOLS_CONSTRAINT_SOLVER_CONSTRAINT_SOLVERI_H_