}
          p.next = null; // help GC
          break;
        }
      }
    }
  }

  /*
   * Methods that loop waiting on a guard's condition until the guard is satisfied, while recording
   * this fact so that other threads know to check our guard and signal us. It's caller's
   * responsibility to ensure that the guard is *not* currently satisfied.
   */

  @GuardedBy("lock")

  }

  /**
   * Enable the accumulation of {@link CacheStats} during the operation of the cache. Without this
   * {@link Cache#stats} will return zero for all statistics. Note that recording stats requires
   * bookkeeping to be performed with each operation, and thus imposes a performance penalty on
   * cache operation.
   *
   * @return this {@code CacheBuilder} instance (for chaining)

    TF_RETURN_IF_ERROR(vspace_.CallBackwardFunction(
        op_type, backward_function.get(), unneeded_gradients, forwardprop_aids,
        absl::MakeSpan(grad)));
  }

  // Stop the tape from recording
  pop_backward_tape.release()();

  std::vector<int64_t> targets;
  std::vector<Gradient*> used_in_grads;
  // We may end up with slightly fewer elements than we reserve, but grad.size()

	FakeP    = 1000000 + iota
	TimerP   // contains timer unblocks
	NetpollP // contains network unblocks
	SyscallP // contains returns from syscalls
	GCP      // contains GC state
	ProfileP // contains recording of CPU profile samples
)

// Trace is the result of Parse.
type Trace struct {
	Version version.Version

	// Events is the sorted list of Events in the trace.
	Events Events