Getting started with importing Keras Sequential models

Let’s say you start with defining a simple MLP using Keras:

from keras.models import Sequential
from keras.layers import Dense
model = Sequential()
model.add(Dense(units=64, activation='relu', input_dim=100))
model.add(Dense(units=10, activation='softmax'))
model.compile(loss='categorical_crossentropy',optimizer='sgd', metrics=['accuracy'])

In Keras there are several ways to save a model. You can store the whole model(model definition, weights and training configuration) as HDF5 file, just themodel configuration (as JSON or YAML file) or just the weights (as HDF5 file).Here’s how you do each:

model.save('full_model.h5')  # save everything in HDF5 format
model_json = model.to_json()  # save just the config. replace with "to_yaml" for YAML serialization
with open("model_config.json", "w") as f:
    f.write(model_json)
model.save_weights('model_weights.h5') # save just the weights.

If you decide to save the full model, you will have access to the training configuration ofthe model, otherwise you don’t. So if you want to further train your model in DL4J after import,keep that in mind and use model.save(…) to persist your model.

Loading your Keras model

Let’s start with the recommended way, loading the full model back into DL4J (we assume it’son your class path):

String fullModel = new ClassPathResource("full_model.h5").getFile().getPath();
MultiLayerNetwork model = KerasModelImport.importKerasSequentialModelAndWeights(fullModel);

In case you didn’t compile your Keras model, it will not come with a training configuration.In that case you need to explicitly tell model import to ignore training configuration bysetting the enforceTrainingConfig flag to false like this:

MultiLayerNetwork model = KerasModelImport.importKerasSequentialModelAndWeights(fullModel, false);

To load just the model configuration from JSON, you use KerasModelImport as follows:

String modelJson = new ClassPathResource("model_config.json").getFile().getPath();
MultiLayerNetworkConfiguration modelConfig = KerasModelImport.importKerasSequentialConfiguration(modelJson)

If additionally you also want to load the model weights with the configuration, here’s what you do:

String modelWeights = new ClassPathResource("model_weights.h5").getFile().getPath();
MultiLayerNetwork network = KerasModelImport.importKerasSequentialModelAndWeights(modelJson, modelWeights)

In the latter two cases no training configuration will be read.