import tensorflow as tf

    # We run the summaries in the same thread as the training operations by
    # passing in None for summary_op to avoid a summary_thread being started.
    # Running summaries and training operations in parallel could run out of
    # GPU memory.
    sv = tf.train.Supervisor(
        is_chief=is_chief,
        logdir=FLAGS.train_dir,
        saver=tf.train.Saver(tf.global_variables()),
        global_step=global_step,
        summary_op=None,
        save_model_secs=FLAGS.save_model_secs,
        summary_writer=summary_writer)

    step_train_times = []
