ML – Saving a Deep Learning model in Keras

Training a neural network/deep learning model usually takes a lot of time, particularly if the hardware capacity of the system doesn’t match up to the requirement. Once the training is done, we save the model to a file. To reuse the model at a later point of time to make predictions, we load the saved model.
Through Keras, models can be saved in three formats:

• YAML format
• JSON format
• HDF5 format

YAML and JSON files store only model structure, whereas, HDF5 file stores complete neural network model along with structure and weights. Therefore, if the model structure is saved using YAML or JSON format, weights should be stored in an HDF5 file to store the entire model.
Considering Boston house prices dataset:
Code: Loading the dataset and preprocessing the data

import keras
from keras.datasets import boston_housing

(train_data, train_targets), (test_data, test_targets)= boston_housing.load_data()

mean = train_data.mean(axis = 0)
train_data-= mean
std = train_data.std(axis = 0)

train_data/= std
test_data-= mean
test_data/= std

Code: Training a neural network model on it

from keras import models
from keras import layers

model = models.Sequential()
model.add(layers.Dense(64, activation ="relu", input_shape =(train_data.shape[1], )))
model.add(layers.Dense(64, activation ="relu"))
model.add(layers.Dense(1))
model.compile(optimizer ="rmsprop", loss ="mse", metrics =["mae"])
loss, accuracy = model.evaluate(test_data, test_targets)

Output:

Code: Saving and reloading model in HDF5 file format

from keras.models import load_model
model.save("network.h5")
loaded_model = load_model("network.h5")
loss, accuracy = loaded_model.evaluate(test_data, test_targets)

Output:

Code: Saving and reloading model in JSON file format

# Saving model structure to a JSON file

model_json = model.to_json() # with open("network.json", "w") as json_file:
    json_file.write(model_json)

# Saving weights of the model to a HDF5 file
model.save_weights("network.h5")

# Loading JSON file
json_file = open("network.json", 'r')
loaded_model_json = json_file.read()
json_file.close()
loaded_model = model_from_json(loaded_model_json)

# Loading weights
loaded_model.load_weights("network.h5")
loss, accuracy = loaded_model.evaluate(test_data, test_targets)

Code: Saving and reloading model in YAML file format

# Saving model structure to a YAML file
model_yaml = model.to_yaml()
with open("network.yaml", "w") as yaml_file:
    yaml_file.write(model_yaml)

# Saving weights of the model to a HDF5 file
model.save_weights("network.h5")

# Loading YAML file
yaml_file = open("network.yaml", 'r')
loaded_model_yaml = yaml_file.read()
yaml_file.close()
loaded_model = model_from_yaml(loaded_model_yaml)

# Loading weights
loaded_model.load_weights("network.h5")
loss, accuracy = loaded_model.evaluate(test_data, test_targets)