tensorflow中callbacks

tf.keras.callbacks是回调函数，在训练过程中可以访问用来做一些决策

1. tf.keras.callbacks.EarlyStopping早停函数，当监控目标monitor训练patience轮都不下降时，结束训练

tf.keras.callbacks.EarlyStopping(
    monitor='val_loss',
    min_delta=0,
    patience=0,
    verbose=0,
    mode='auto',
    baseline=None,
    restore_best_weights=False
)

2. tf.keras.callbacks.LearningRateScheduler学习率衰减函数
   自己实现scheduler函数设置学习率衰减形式
   3. tf.keras.callbacks.ModelCheckpoint每轮训练结束用来保存模型权重

tf.keras.callbacks.ModelCheckpoint(
    filepath,
    monitor='val_loss',
    verbose=0,
    save_best_only=False,
    save_weights_only=False,
    mode='auto',
    save_freq='epoch',
    options=None,
    initial_value_threshold=None,
    **kwargs
)

4. tf.keras.callbacks.TensorBoard可视化训练过程

tf.keras.callbacks.TensorBoard(
    log_dir='logs',
    histogram_freq=0,
    write_graph=True,
    write_images=False,
    write_steps_per_second=False,
    update_freq='epoch',
    profile_batch=0,
    embeddings_freq=0,
    embeddings_metadata=None,
    **kwargs
)