tensorflow - 失败前提条件错误 : Attempting to use uninitialized value Adam/lr

Question

我正在训练一个 VGG16 微调模型。在第一个 epoch 之后，程序停止并给出了这个错误:

下面是我用于模型的代码:

# create a copy of a mobilenet model
import keras
vgg_model=keras.applications.vgg16.VGG16()

type(vgg_model)

vgg_model.summary()

from keras.models import Sequential
model = Sequential()
for layer in vgg_model.layers[:-1]:
    model.add(layer)

model.summary()

# CREATE THE MODEL ARCHITECTURE
from keras.layers import Dense, Activation, Dropout

model.add(Dropout(0.25))
model.add(Dense(7,activation='softmax'))

model.summary()

#Train the Model
# Define Top2 and Top3 Accuracy

from keras.metrics import categorical_accuracy, top_k_categorical_accuracy

def top_3_accuracy(y_true, y_pred):
    return top_k_categorical_accuracy(y_true, y_pred, k=3)

def top_2_accuracy(y_true, y_pred):
    return top_k_categorical_accuracy(y_true, y_pred, k=2)

from keras.optimizers import Adam
model.compile(Adam(lr=0.01), loss='categorical_crossentropy', 
              metrics=[categorical_accuracy, top_2_accuracy, top_3_accuracy])

# Get the labels that are associated with each index
print(valid_batches.class_indices)

# Add weights to try to make the model more sensitive to melanoma

class_weights={
    0: 1.0, # akiec
    1: 1.0, # bcc
    2: 1.0, # bkl
    3: 1.0, # df
    4: 3.0, # mel # Try to make the model more sensitive to Melanoma.
    5: 1.0, # nv
    6: 1.0, # vasc
}

filepath = "skin.h5"
checkpoint = ModelCheckpoint(filepath, monitor='val_top_3_accuracy', verbose=1, 
                             save_best_only=True, mode='max')

reduce_lr = ReduceLROnPlateau(monitor='val_top_3_accuracy', factor=0.5, patience=2, 
                                   verbose=1, mode='max', min_lr=0.00001)
                              
                              
callbacks_list = [checkpoint, reduce_lr]

history = model.fit_generator(train_batches, steps_per_epoch=train_steps, 
                              class_weight=class_weights,
                    validation_data=valid_batches,
                    validation_steps=val_steps,
                    epochs=40, verbose=1,
                   callbacks=callbacks_list)

我正在尝试学习如何在图像数据集上微调、训练和使用 VGG16 模型。我在关注这个blog他使用 mobileNet 的地方。

我在关注这个 VGG16 tutorial为模型编写代码。

如果有人可以帮助我修复此错误或解释它是如何以及为什么发生的，我将非常感谢您的帮助。

依赖关系:

• tensorflow 1.12.0
• tensorflow-GPU 1.12.0
• python 3.6.0
• keras 2.2.4

Answer 1

我在使用 ReduceLROnPlateau 回调时遇到了同样的错误。除非绝对必要，否则您可以省略它的用法。