message: Init struct bools to false to prevent warnings by dynamic
  type checking programs when an uninitialized value is read
  by operator=.
diff: @@ -80,7 +80,7 @@ struct CollInstanceParams {
  // Task name prefix of corresponding device name.
  std::vector<string> task_names;
  // True if every task has the same number of devices.
  - bool same_num_devices_per_task;
  + bool same_num_devices_per_task = false;
  CollImplDetails impl_details;
  string ToString() const;
  CollInstanceParams& operator=(const struct CollInstanceParams& other);
  @@ -101,7 +101,7 @@ struct CollectiveParams {
  string name; // node name used only for log or error messages
  int default_rank; // index of this op within device_names
  - bool is_source; // broadcast only
  + bool is_source = false; // broadcast only
  // Rank of this device in each subdivision permutation.
  std::vector<int> subdiv_rank;
  std::unique_ptr<OpKernel> merge_op; // reduction only
  