Keras fit freezes at the end of the first epoch

问题

I am currently experimenting with fine tuning the VGG16 network using Keras.

I started tweaking a little bit with the cats and dogs dataset.

However, with the current configuration the training seems to block on the first epoch

from keras import applications
from keras.preprocessing.image import ImageDataGenerator
from keras import optimizers
from keras.models import Sequential, Model
from keras.layers import Dropout, Flatten, Dense


img_width, img_height = 224, 224

train_data_dir = 'data/train'
validation_data_dir = 'data/validation'
nb_train_samples = 2000
nb_validation_samples = 800
epochs = 50
batch_size = 20


model = applications.VGG16(weights='imagenet', include_top=False , input_shape=(224,224,3))
print('Model loaded.')


top_model = Sequential()
top_model.add(Flatten(input_shape=model.output_shape[1:]))
top_model.add(Dense(256, activation='relu',name='newlayer'))
top_model.add(Dropout(0.5))
top_model.add(Dense(2, activation='softmax'))


model = Model(inputs= model.input, outputs= top_model(model.output))


for layer in model.layers[:19]:
    layer.trainable = False


model.compile(loss='categorical_crossentropy',
              optimizer=optimizers.Adam(lr=0.0001),
              metrics=['accuracy'])

train_datagen = ImageDataGenerator(
    rescale=1. / 255,
    shear_range=0.2,
    zoom_range=0.2,
    horizontal_flip=True)

test_datagen = ImageDataGenerator(rescale=1. / 255)

train_generator = train_datagen.flow_from_directory(
    train_data_dir,
    target_size=(img_height, img_width),
    batch_size=batch_size,
    shuffle=True,
    class_mode='categorical')

validation_generator = test_datagen.flow_from_directory(
    validation_data_dir,
    target_size=(img_height, img_width),
    batch_size=batch_size,
    class_mode='categorical')


model.fit_generator(
    train_generator,
    steps_per_epoch=nb_train_samples// batch_size,
    epochs=epochs,
    validation_data=validation_generator,
    validation_steps=nb_validation_samples)

Last output:

Epoch 1/50 99/100 [============================>.] - ETA: 0s - loss: 0.5174 - acc: 0.7581

Am I missing something ?

回答1:

I faced this problem in Co-Lab provides limited memory upto(12 GB) in cloud which creates many issues while solving a problem. That's why only 300 images are used to train and test.when images was preprocessed with dimension 600x600 and batch size was set to 128 it Keras model freezed during epoch 1 .Compiler did not show this error.Actually the error was runtime limited memory which was unable to handle by CoLab because it gave only 12GB limited memory for usage. Solution to above mentioned problem was solved by changing batch size to 4 and reduce image dimension to 300x300 because with 600x600 it still not work.
Conclusively,Recommend Solution is Make Images dimension and Batch_size small until you get no error Run Again and Again until there will no run time error

来源：https://stackoverflow.com/questions/48748413/keras-fit-freezes-at-the-end-of-the-first-epoch

标签

tensorflow

keras

conv-neural-network