加载训练有素的Keras模型并继续训练

问题描述

我想知道是否有可能保存经过部分训练的Keras模型并在再次加载模型后继续进行训练.

I was wondering if it was possible to save a partly trained Keras model and continue the training after loading the model again.

这样做的原因是，将来我将拥有更多的训练数据，并且我不想再次对整个模型进行训练.

The reason for this is that I will have more training data in the future and I do not want to retrain the whole model again.

我正在使用的功能是:

#Partly train model
model.fit(first_training, first_classes, batch_size=32, nb_epoch=20)

#Save partly trained model
model.save('partly_trained.h5')

#Load partly trained model
from keras.models import load_model
model = load_model('partly_trained.h5')

#Continue training
model.fit(second_training, second_classes, batch_size=32, nb_epoch=20)

---

添加了完整的示例

第一个数据集在10个纪元后，最后一个纪元的损失为0.0748，准确度为0.9863.

With the first dataset after 10 epochs the loss of the last epoch will be 0.0748 and the accuracy 0.9863.

保存，删除和重新加载模型后，第二个数据集上训练的模型的损失和准确性分别为0.1711和0.9504.

After saving, deleting and reloading the model the loss and accuracy of the model trained on the second dataset will be 0.1711 and 0.9504 respectively.

这是由新的训练数据还是完全重新训练的模型引起的?

Is this caused by the new training data or by a completely re-trained model?

"""
Model by: http://machinelearningmastery.com/
"""
# load (downloaded if needed) the MNIST dataset
import numpy
from keras.datasets import mnist
from keras.models import Sequential
from keras.layers import Dense
from keras.utils import np_utils
from keras.models import load_model
numpy.random.seed(7)

def baseline_model():
    model = Sequential()
    model.add(Dense(num_pixels, input_dim=num_pixels, init='normal', activation='relu'))
    model.add(Dense(num_classes, init='normal', activation='softmax'))
    model.compile(loss='categorical_crossentropy', optimizer='adam', metrics=['accuracy'])
    return model

if __name__ == '__main__':
    # load data
    (X_train, y_train), (X_test, y_test) = mnist.load_data()

    # flatten 28*28 images to a 784 vector for each image
    num_pixels = X_train.shape[1] * X_train.shape[2]
    X_train = X_train.reshape(X_train.shape[0], num_pixels).astype('float32')
    X_test = X_test.reshape(X_test.shape[0], num_pixels).astype('float32')
    # normalize inputs from 0-255 to 0-1
    X_train = X_train / 255
    X_test = X_test / 255
    # one hot encode outputs
    y_train = np_utils.to_categorical(y_train)
    y_test = np_utils.to_categorical(y_test)
    num_classes = y_test.shape[1]

    # build the model
    model = baseline_model()

    #Partly train model
    dataset1_x = X_train[:3000]
    dataset1_y = y_train[:3000]
    model.fit(dataset1_x, dataset1_y, nb_epoch=10, batch_size=200, verbose=2)

    # Final evaluation of the model
    scores = model.evaluate(X_test, y_test, verbose=0)
    print("Baseline Error: %.2f%%" % (100-scores[1]*100))

    #Save partly trained model
    model.save('partly_trained.h5')
    del model

    #Reload model
    model = load_model('partly_trained.h5')

    #Continue training
    dataset2_x = X_train[3000:]
    dataset2_y = y_train[3000:]
    model.fit(dataset2_x, dataset2_y, nb_epoch=10, batch_size=200, verbose=2)
    scores = model.evaluate(X_test, y_test, verbose=0)
    print("Baseline Error: %.2f%%" % (100-scores[1]*100))

推荐答案

实际上-model.save保存了根据您的情况重新开始培训所需的所有信息.重新加载模型可能会破坏的唯一事情是优化器状态.要进行检查，请尝试save并重新加载模型，并根据训练数据对其进行训练.

Actually - model.save saves all information need for restarting training in your case. The only thing which could be spoiled by reloading model is your optimizer state. To check that - try to save and reload model and train it on training data.

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