import tensorflow as tf

    """Run cnn in benchmark mode. When forward_only on, it forwards CNN."""
    (enqueue_ops, fetches) = self._build_model()
    main_fetch_group = tf.group(*fetches)
    execution_barrier = None
    if self.job_name and not FLAGS.cross_replica_sync:
      execution_barrier = self.add_sync_queues_and_barrier(
          'execution_barrier_', [])

    global_step = tf.contrib.framework.get_global_step()
    with tf.device(self.global_step_device):
      with tf.control_dependencies([main_fetch_group]):
        inc_global_step = global_step.assign_add(1)
        fetches.append(inc_global_step)

    if self.job_name and FLAGS.cross_replica_sync:
      # Block all replicas until all replicas are ready for next step.
      fetches.append(self.add_sync_queues_and_barrier(
          'sync_queues_step_end_', [main_fetch_group]))

    variable_mgr_post_init_ops = self.variable_mgr.get_post_init_ops()
