keras/examples/mnist_irnn.py

from __future__ import absolute_import
from __future__ import print_function
import numpy as np
np.random.seed(1337) # for reproducibility

from keras.datasets import mnist
from keras.models import Sequential
from keras.layers.core import Dense, Activation
from keras.initializations import normal, identity
from keras.layers.recurrent import SimpleRNN, LSTM
from keras.optimizers import RMSprop
from keras.utils import np_utils

'''
    This is a reproduction of the IRNN experiment
    with pixel-by-pixel sequential MNIST in
    "A Simple Way to Initialize Recurrent Networks of Rectified Linear Units "
    by Quoc V. Le, Navdeep Jaitly, Geoffrey E. Hinton

    arXiv:1504.00941v2 [cs.NE] 7 Apr 201
    http://arxiv.org/pdf/1504.00941v2.pdf

    Optimizer is replaced with RMSprop which yields more stable and steady
    improvement.

    Reaches 0.93 train/test accuracy after 900 epochs (which roughly corresponds
    to 1687500 steps in the original paper.)
'''

batch_size = 32
nb_classes = 10
nb_epochs = 200
hidden_units = 100

learning_rate = 1e-6
clip_norm = 1.0
BPTT_truncate = 28*28

# the data, shuffled and split between train and test sets
(X_train, y_train), (X_test, y_test) = mnist.load_data()

X_train = X_train.reshape(X_train.shape[0], -1, 1)
X_test = X_test.reshape(X_test.shape[0], -1, 1)
X_train = X_train.astype("float32")
X_test = X_test.astype("float32")
X_train /= 255
X_test /= 255
print('X_train shape:', X_train.shape)
print(X_train.shape[0], 'train samples')
print(X_test.shape[0], 'test samples')

# convert class vectors to binary class matrices
Y_train = np_utils.to_categorical(y_train, nb_classes)
Y_test = np_utils.to_categorical(y_test, nb_classes)

print('Evaluate IRNN...')
model = Sequential()
model.add(SimpleRNN(input_dim=1, output_dim=hidden_units,
                    init=lambda shape: normal(shape, scale=0.001),
                    inner_init=lambda shape: identity(shape, scale=1.0),
                    activation='relu', truncate_gradient=BPTT_truncate))
model.add(Dense(hidden_units, nb_classes))
model.add(Activation('softmax'))
rmsprop = RMSprop(lr=learning_rate)
model.compile(loss='categorical_crossentropy', optimizer=rmsprop)

model.fit(X_train, Y_train, batch_size=batch_size, nb_epoch=nb_epochs,
          show_accuracy=True, verbose=1, validation_data=(X_test, Y_test))

scores = model.evaluate(X_test, Y_test, show_accuracy=True, verbose=0)
print('IRNN test score:', scores[0])
print('IRNN test accuracy:', scores[1])

print('Compare to LSTM...')
model = Sequential()
model.add(LSTM(1, hidden_units))
model.add(Dense(hidden_units, nb_classes))
model.add(Activation('softmax'))
rmsprop = RMSprop(lr=learning_rate)
model.compile(loss='categorical_crossentropy', optimizer=rmsprop)

model.fit(X_train, Y_train, batch_size=batch_size, nb_epoch=nb_epochs,
          show_accuracy=True, verbose=1, validation_data=(X_test, Y_test))

scores = model.evaluate(X_test, Y_test, show_accuracy=True, verbose=0)
print('LSTM test score:', scores[0])
print('LSTM test accuracy:', scores[1])