加载保存的模型以恢复训练

Question

我正在训练 ResNet 模型来对汽车品牌进行分类。

我在训练期间为每个 epoch 保存了权重。

为了测试，我在 epoch 3 停止了训练。

# checkpoint = ModelCheckpoint("best_model.hdf5", monitor='loss', verbose=1)
checkpoint_path = "weights/cp-{epoch:04d}.ckpt"
checkpoint_dir = os.path.dirname(checkpoint_path)

cp_callback = tf.keras.callbacks.ModelCheckpoint(
   checkpoint_path, verbose=1, 
   # Save weights, every epoch.
   save_freq='epoch')

model.save_weights(checkpoint_path.format(epoch=0))

history = model.fit_generator(
    training_set,
    validation_data = test_set,
    epochs = 50,
    steps_per_epoch = len(training_set),
    validation_steps = len(test_set),
    callbacks = [cp_callback]
)

但是，当加载它们时，我不确定它是否从上次保存的纪元恢复，因为它再次显示纪元 1/50。下面是我用来加载上次保存的模型的代码。

from keras.models import Sequential, load_model
# load the model
new_model = load_model('./weights/cp-0003.ckpt')

# fit the model
history = new_model.fit_generator(
    training_set,
    validation_data = test_set,
    epochs = 50,
    steps_per_epoch = len(training_set),
    validation_steps = len(test_set),
    callbacks = [cp_callback]
)

这是它的样子： Image showing that running the saved weight starts from epoch 1/50 again

有人可以帮忙吗？

Answer 1

您可以使用 fit_generator 的 initial_epoch 参数。默认情况下，它设置为 0，但您可以将其设置为任何正数：

from keras.models import Sequential, load_model
import tensorflow as tf

checkpoint_path = "weights/cp-{epoch:04d}.ckpt"
checkpoint_dir = os.path.dirname(checkpoint_path)

cp_callback = tf.keras.callbacks.ModelCheckpoint(
   checkpoint_path, verbose=1, 
   # Save weights, every epoch.
   save_freq='epoch')

model.save_weights(checkpoint_path.format(epoch=0))

history = model.fit_generator(
    training_set,
    validation_data=test_set,
    epochs=3,
    steps_per_epoch=len(training_set),
    validation_steps=len(test_set),
    callbacks = [cp_callback]
)


new_model = load_model('./weights/cp-0003.ckpt')

# fit the model
history = new_model.fit_generator(
    training_set,
    validation_data=test_set,
    epochs=50,
    steps_per_epoch=len(training_set),
    validation_steps=len(test_set),
    callbacks=[cp_callback],
    initial_epoch=3
)

这将为您的模型训练 50 - 3 = 47 个额外的时期。

如果您使用 Tensorflow 2.X 关于您的代码的一些评论：

fit_generator 已弃用，因为 fit 现在支持生成器
您应该将导入 from keras.... 替换为 from tensorflow.keras...

加载保存的模型以恢复训练

Loading a saved model to resume training

python

tensorflow

machine-learning

keras

resnet