EVOLUTION-MANAGER

Edit File: union_find.h

Licensed under the Apache License, Version 2.0 (the "License");
you may not use this file except in compliance with the License.
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==============================================================================*/

#ifndef TENSORFLOW_COMPILER_JIT_UNION_FIND_H_
#define TENSORFLOW_COMPILER_JIT_UNION_FIND_H_

namespace tensorflow {

// Union-Find data structure.
// Each cluster has an associated value; when merging clusters we can control
// which value becomes the representative of the merged clusters. Values must be
// copyable.
template <typename T>
class UnionFind {
 public:
  UnionFind() : rank_(0), size_(1), parent_(nullptr) {}

// Returns the number of elements in a cluster.
  int Size() { return FindRoot()->size_; }

// Merges this cluster with 'other'. This cluster's value becomes
  // the value of the merged cluster; the value of 'other' is ignored.
  void Merge(UnionFind* other);

// Each cluster has an associated value. Retrieves the value associated
  // with this cluster.
  T& Get() { return FindRoot()->value_; }

private:
  // Finds the root element of the cluster. Performs path compression.
  UnionFind* FindRoot();

int rank_;
  int size_;  // Size of the cluster.
  UnionFind* parent_;
  T value_;
};

template <typename T>
void UnionFind<T>::Merge(UnionFind* other) {
  UnionFind<T>* a = FindRoot();
  UnionFind<T>* b = other->FindRoot();
  if (a == b) return;
  if (a->rank_ > b->rank_) {
    b->parent_ = a;
    a->size_ += b->size_;
    return;
  }

a->parent_ = b;
  if (a->rank_ == b->rank_) {
    b->rank_++;
  }
  b->value_ = a->value_;
  b->size_ += a->size_;
}

template <typename T>
UnionFind<T>* UnionFind<T>::FindRoot() {
  if (!parent_) return this;
  // Path compression: update intermediate nodes to point to the root of the
  // equivalence class.
  parent_ = parent_->FindRoot();
  return parent_;
}

}  // namespace tensorflow

#endif  // TENSORFLOW_COMPILER_JIT_UNION_FIND_H_