In [1]:
# These are all the modules we'll be using later. Make sure you can import them
# before proceeding further.
import numpy as np
import tensorflow as tf
from __future__ import print_function
from six.moves import cPickle as pickle
First reload the data we generated in notmist.ipynb.
In [2]:
pickle_file = 'notMNIST.pickle'
with open(pickle_file, 'rb') as f:
save = pickle.load(f)
train_dataset = save['train_dataset']
train_labels = save['train_labels']
valid_dataset = save['valid_dataset']
valid_labels = save['valid_labels']
test_dataset = save['test_dataset']
test_labels = save['test_labels']
del save # hint to help gc free up memory
print('Training set', train_dataset.shape, train_labels.shape)
print('Validation set', valid_dataset.shape, valid_labels.shape)
print('Test set', test_dataset.shape, test_labels.shape)
Reformat into a shape that's more adapted to the models we're going to train:
In [3]:
image_size = 28
num_labels = 10
def reformat(dataset, labels):
dataset = dataset.reshape((-1, image_size * image_size)).astype(np.float32)
# Map 2 to [0.0, 1.0, 0.0 ...], 3 to [0.0, 0.0, 1.0 ...]
labels = (np.arange(num_labels) == labels[:,None]).astype(np.float32)
return dataset, labels
train_dataset, train_labels = reformat(train_dataset, train_labels)
valid_dataset, valid_labels = reformat(valid_dataset, valid_labels)
test_dataset, test_labels = reformat(test_dataset, test_labels)
print('Training set', train_dataset.shape, train_labels.shape)
print('Validation set', valid_dataset.shape, valid_labels.shape)
print('Test set', test_dataset.shape, test_labels.shape)
In [4]:
def accuracy(predictions, labels):
return (100.0 * np.sum(np.argmax(predictions, 1) == np.argmax(labels, 1))
/ predictions.shape[0])
Introduce and tune L2 regularization for both logistic and neural network models. Remember that L2 amounts to adding a penalty on the norm of the weights to the loss. In TensorFlow, you can compute the L2 loss for a tensor t using nn.l2_loss(t). The right amount of regularization should improve your validation / test accuracy.
In [5]:
# fixed variables
# Subset the training data for faster turnaround.
train_subset = 50000
# batch size for sgd
batch_size = 512
In [6]:
# create computation graph for logistic regression with regularization
logRegGraph = tf.Graph()
with logRegGraph.as_default():
# input data
tf_test_dataset = tf.constant(test_dataset)
tf_valid_dataset = tf.constant(valid_dataset)
tf_train_labels = tf.placeholder(tf.float32,shape=(batch_size,num_labels))
tf_train_dataset = tf.placeholder(tf.float32,shape=(batch_size,image_size*image_size))
# variables
biases = tf.Variable(tf.zeros([num_labels]))
weights = tf.Variable(tf.truncated_normal([image_size*image_size,num_labels]))
# regularization constant
beta = tf.constant(5e-3)
# training computation.
logits = tf.matmul(tf_train_dataset,weights)+biases
loss = tf.reduce_mean(tf.nn.softmax_cross_entropy_with_logits(logits,tf_train_labels)) \
+ beta*tf.nn.l2_loss(weights)
# optimizer
optimizer = tf.train.GradientDescentOptimizer(0.5).minimize(loss)
# predictions for the training, validation, and test data
train_prediction = tf.nn.softmax(logits)
test_prediction = tf.nn.softmax(tf.matmul(tf_test_dataset, weights) + biases)
valid_prediction = tf.nn.softmax(tf.matmul(tf_valid_dataset, weights) + biases)
In [7]:
num_steps = 2001
with tf.Session(graph=logRegGraph) as session:
tf.initialize_all_variables().run()
for step in range(num_steps):
# offset to sample data
offset = (step*batch_size)%(train_labels.shape[0]-batch_size)
# generate a minibatch.
batch_data = train_dataset[offset:(offset+batch_size),:]
batch_labels = train_labels[offset:(offset+batch_size),:]
# prepare dictionary with the minibatch.
feed_dict = {tf_train_dataset:batch_data,tf_train_labels:batch_labels}
_, l, predictions = session.run([optimizer, loss, train_prediction], feed_dict=feed_dict)
if (step%500 == 0):
print("Minibatch loss at step %d: %f" % (step, l))
print("Minibatch accuracy: %.1f%%" % accuracy(predictions, batch_labels))
print("Validation accuracy: %.1f%%" % accuracy(valid_prediction.eval(), valid_labels))
print("Test accuracy: %.1f%%" % accuracy(test_prediction.eval(), test_labels))
In [8]:
batch_size = 512
num_hidden = 1024
nnGraph = tf.Graph()
with nnGraph.as_default():
# input data
tf_test_dataset = tf.constant(test_dataset)
tf_valid_dataset = tf.constant(valid_dataset)
tf_train_labels = tf.placeholder(tf.float32,shape=(batch_size,num_labels))
tf_hidden_units = tf.placeholder(tf.float32,shape=(batch_size,image_size*image_size))
tf_train_dataset = tf.placeholder(tf.float32,shape=(batch_size,image_size*image_size))
# variables.
biases1 = tf.Variable(tf.zeros([num_hidden]))
biases2 = tf.Variable(tf.zeros([num_labels]))
weights1 = tf.Variable(tf.truncated_normal([image_size*image_size,num_hidden]))
weights2 = tf.Variable(tf.truncated_normal([num_hidden,num_labels]))
# regularization constants
beta1 = tf.constant(5e-3)
beta2 = tf.constant(5e-3)
# training computation.
tf_hidden_units = tf.nn.relu(tf.matmul(tf_train_dataset, weights1)+biases1)
logits = tf.matmul(tf_hidden_units, weights2)+biases2
loss = tf.reduce_mean(tf.nn.softmax_cross_entropy_with_logits(logits,tf_train_labels)) \
+ beta1*tf.nn.l2_loss(weights1) + beta2*tf.nn.l2_loss(weights2)
# Optimizer.
optimizer = tf.train.GradientDescentOptimizer(0.5).minimize(loss)
# Predictions for the training, validation, and test data.
train_prediction = tf.nn.softmax(logits)
test_prediction = tf.nn.softmax(tf.matmul(tf.nn.relu(tf.matmul(tf_test_dataset,weights1)+biases1),
weights2)+biases2)
valid_prediction = tf.nn.softmax(tf.matmul(tf.nn.relu(tf.matmul(tf_valid_dataset,weights1)+biases1),
weights2)+biases2)
In [9]:
num_steps = 2001
with tf.Session(graph=nnGraph) as session:
tf.initialize_all_variables().run()
print("Initialized")
for step in range(num_steps):
# Pick an offset within the training data, which has been randomized.
# Note: we could use better randomization across epochs.
offset = (step*batch_size)%(train_labels.shape[0]-batch_size)
# Generate a minibatch.
batch_data = train_dataset[offset:(offset+batch_size),:]
batch_labels = train_labels[offset:(offset+batch_size),:]
# Prepare a dictionary telling the session where to feed the minibatch.
# The key of the dictionary is the placeholder node of the graph to be fed,
# and the value is the numpy array to feed to it.
feed_dict = {tf_train_dataset:batch_data,tf_train_labels:batch_labels}
_, l, predictions = session.run([optimizer, loss, train_prediction], feed_dict=feed_dict)
if (step%500 == 0):
print("Minibatch loss at step %d: %f" % (step, l))
print("Minibatch accuracy: %.1f%%" % accuracy(predictions, batch_labels))
print("Validation accuracy: %.1f%%" % accuracy(valid_prediction.eval(), valid_labels))
print("Test accuracy: %.1f%%" % accuracy(test_prediction.eval(), test_labels))
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batch_size = 64
num_hidden = 1024
train_subset = 500
nnGraph = tf.Graph()
with nnGraph.as_default():
# input data
tf_test_dataset = tf.constant(test_dataset)
tf_valid_dataset = tf.constant(valid_dataset)
tf_train_labels = tf.placeholder(tf.float32,shape=(batch_size,num_labels))
tf_hidden_units = tf.placeholder(tf.float32,shape=(batch_size,image_size*image_size))
tf_train_dataset = tf.placeholder(tf.float32,shape=(batch_size,image_size*image_size))
# variables.
biases1 = tf.Variable(tf.zeros([num_hidden]))
biases2 = tf.Variable(tf.zeros([num_labels]))
weights1 = tf.Variable(tf.truncated_normal([image_size*image_size,num_hidden]))
weights2 = tf.Variable(tf.truncated_normal([num_hidden,num_labels]))
# regularization constants
beta1 = tf.constant(0.0)
beta2 = tf.constant(0.0)
# training computation.
tf_hidden_units = tf.nn.relu(tf.matmul(tf_train_dataset, weights1)+biases1)
logits = tf.matmul(tf_hidden_units, weights2)+biases2
loss = tf.reduce_mean(tf.nn.softmax_cross_entropy_with_logits(logits,tf_train_labels)) \
+ beta1*tf.nn.l2_loss(weights1) + beta2*tf.nn.l2_loss(weights2)
# Optimizer.
optimizer = tf.train.GradientDescentOptimizer(0.5).minimize(loss)
# Predictions for the training, validation, and test data.
train_prediction = tf.nn.softmax(logits)
test_prediction = tf.nn.softmax(tf.matmul(tf.nn.relu(tf.matmul(tf_test_dataset,weights1)+biases1),
weights2)+biases2)
valid_prediction = tf.nn.softmax(tf.matmul(tf.nn.relu(tf.matmul(tf_valid_dataset,weights1)+biases1),
weights2)+biases2)
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num_steps = 5001
with tf.Session(graph=nnGraph) as session:
tf.initialize_all_variables().run()
print("Initialized")
for step in range(num_steps):
# Pick an offset within the training data, which has been randomized.
# Note: we could use better randomization across epochs.
offset = (step*batch_size)%(train_subset-batch_size)
# Generate a minibatch.
batch_data = train_dataset[offset:(offset+batch_size),:]
batch_labels = train_labels[offset:(offset+batch_size),:]
# Prepare a dictionary telling the session where to feed the minibatch.
# The key of the dictionary is the placeholder node of the graph to be fed,
# and the value is the numpy array to feed to it.
feed_dict = {tf_train_dataset:batch_data,tf_train_labels:batch_labels}
_, l, predictions = session.run([optimizer, loss, train_prediction], feed_dict=feed_dict)
if (step%500 == 0):
print("Minibatch loss at step %d: %f" % (step, l))
print("Minibatch accuracy: %.1f%%" % accuracy(predictions, batch_labels))
print("Validation accuracy: %.1f%%" % accuracy(valid_prediction.eval(), valid_labels))
print("Test accuracy: %.1f%%" % accuracy(test_prediction.eval(), test_labels))
Introduce Dropout on the hidden layer of the neural network. Remember: Dropout should only be introduced during training, not evaluation, otherwise your evaluation results would be stochastic as well. TensorFlow provides nn.dropout() for that, but you have to make sure it's only inserted during training.
What happens to our extreme overfitting case?
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batch_size = 64
num_hidden = 1024
train_subset = 500
nnGraph = tf.Graph()
with nnGraph.as_default():
# input data
tf_test_dataset = tf.constant(test_dataset)
tf_valid_dataset = tf.constant(valid_dataset)
tf_train_labels = tf.placeholder(tf.float32,shape=(batch_size,num_labels))
tf_hidden_units = tf.placeholder(tf.float32,shape=(batch_size,image_size*image_size))
tf_train_dataset = tf.placeholder(tf.float32,shape=(batch_size,image_size*image_size))
# variables.
biases1 = tf.Variable(tf.zeros([num_hidden]))
biases2 = tf.Variable(tf.zeros([num_labels]))
weights1 = tf.Variable(tf.truncated_normal([image_size*image_size,num_hidden]))
weights2 = tf.Variable(tf.truncated_normal([num_hidden,num_labels]))
# regularization constants
beta1 = tf.constant(0.0)
beta2 = tf.constant(0.0)
# dropout constant
keep_prob = tf.constant(0.5)
# training computation.
tf_hidden_units = tf.nn.dropout(tf.nn.relu(tf.matmul(tf_train_dataset, weights1)+biases1),keep_prob)
logits = tf.matmul(tf_hidden_units, weights2)+biases2
loss = tf.reduce_mean(tf.nn.softmax_cross_entropy_with_logits(logits,tf_train_labels)) \
+ beta1*tf.nn.l2_loss(weights1) + beta2*tf.nn.l2_loss(weights2)
# Optimizer.
optimizer = tf.train.GradientDescentOptimizer(0.5).minimize(loss)
# Predictions for the training, validation, and test data.
train_prediction = tf.nn.softmax(logits)
test_prediction = tf.nn.softmax(tf.matmul(tf.nn.relu(tf.matmul(tf_test_dataset,weights1)+biases1),
weights2)+biases2)
valid_prediction = tf.nn.softmax(tf.matmul(tf.nn.relu(tf.matmul(tf_valid_dataset,weights1)+biases1),
weights2)+biases2)
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num_steps = 5001
with tf.Session(graph=nnGraph) as session:
tf.initialize_all_variables().run()
print("Initialized")
for step in range(num_steps):
# Pick an offset within the training data, which has been randomized.
# Note: we could use better randomization across epochs.
offset = (step*batch_size)%(train_subset-batch_size)
# Generate a minibatch.
batch_data = train_dataset[offset:(offset+batch_size),:]
batch_labels = train_labels[offset:(offset+batch_size),:]
# Prepare a dictionary telling the session where to feed the minibatch.
# The key of the dictionary is the placeholder node of the graph to be fed,
# and the value is the numpy array to feed to it.
feed_dict = {tf_train_dataset:batch_data,tf_train_labels:batch_labels}
_, l, predictions = session.run([optimizer, loss, train_prediction], feed_dict=feed_dict)
if (step%500 == 0):
print("Minibatch loss at step %d: %f" % (step, l))
print("Minibatch accuracy: %.1f%%" % accuracy(predictions, batch_labels))
print("Validation accuracy: %.1f%%" % accuracy(valid_prediction.eval(), valid_labels))
print("Test accuracy: %.1f%%" % accuracy(test_prediction.eval(), test_labels))
Try to get the best performance you can using a multi-layer model! The best reported test accuracy using a deep network is 97.1%.
One avenue you can explore is to add multiple layers.
Another one is to use learning rate decay:
global_step = tf.Variable(0) # count the number of steps taken.
learning_rate = tf.train.exponential_decay(0.5, global_step, ...)
optimizer = tf.train.GradientDescentOptimizer(learning_rate).minimize(loss, global_step=global_step)
In [12]:
batch_size = 512
train_subset = train_labels.shape[0]
num_hidden_1 = 1024
num_hidden_2 = 256
num_hidden_3 = 64
num_steps = 12001
keep_prob = 0.6
reg_constant = 1e-4
update_steps = 100
update_exponent = 0.96
initial_learning_rate = 6e-3
weight_dev = np.sqrt(1.0/train_subset)
dnnGraph = tf.Graph()
with dnnGraph.as_default():
# input data
tf_test_dataset = tf.constant(test_dataset)
tf_valid_dataset = tf.constant(valid_dataset)
tf_train_labels = tf.placeholder(tf.float32,shape=(batch_size,num_labels))
tf_train_dataset = tf.placeholder(tf.float32,shape=(batch_size,image_size*image_size))
tf_hidden_units_1 = tf.placeholder(tf.float32,shape=(batch_size,num_hidden_1))
tf_hidden_units_2 = tf.placeholder(tf.float32,shape=(batch_size,num_hidden_2))
tf_hidden_units_3 = tf.placeholder(tf.float32,shape=(batch_size,num_hidden_3))
# variables.
biases1 = tf.Variable(tf.zeros([num_hidden_1]))
biases2 = tf.Variable(tf.zeros([num_hidden_2]))
biases3 = tf.Variable(tf.zeros([num_hidden_3]))
biases4 = tf.Variable(tf.zeros([num_labels]))
weights1 = tf.Variable(tf.truncated_normal([image_size*image_size,num_hidden_1],stddev=weight_dev))
weights2 = tf.Variable(tf.truncated_normal([num_hidden_1,num_hidden_2],stddev=weight_dev))
weights3 = tf.Variable(tf.truncated_normal([num_hidden_2,num_hidden_3],stddev=weight_dev))
weights4 = tf.Variable(tf.truncated_normal([num_hidden_3,num_labels],stddev=weight_dev))
# regularization constants
beta = tf.constant(reg_constant)
# dropout constant
keep_prob_1 = tf.constant(keep_prob)
keep_prob_2 = tf.constant(keep_prob)
keep_prob_3 = tf.constant(keep_prob)
# training computation.
def forwardPropwithDrop(data):
tf_hidden_units_1 = tf.nn.dropout(tf.nn.relu(tf.matmul(data,weights1)+biases1),keep_prob_1)
tf_hidden_units_2 = tf.nn.dropout(tf.nn.relu(tf.matmul(tf_hidden_units_1,weights2)+biases2),keep_prob_2)
tf_hidden_units_3 = tf.nn.dropout(tf.nn.relu(tf.matmul(tf_hidden_units_2,weights3)+biases3),keep_prob_3)
logits = tf.matmul(tf_hidden_units_3, weights4)+biases4
return logits
def forwardPropwithoutDrop(data):
tf_hidden_units_1 = tf.nn.relu(tf.matmul(data,weights1)+biases1)
tf_hidden_units_2 = tf.nn.relu(tf.matmul(tf_hidden_units_1,weights2)+biases2)
tf_hidden_units_3 = tf.nn.relu(tf.matmul(tf_hidden_units_2,weights3)+biases3)
logits = tf.matmul(tf_hidden_units_3, weights4)+biases4
return logits
logits = forwardPropwithDrop(tf_train_dataset)
loss = tf.reduce_mean(tf.nn.softmax_cross_entropy_with_logits(logits,tf_train_labels)) \
+ beta*(tf.nn.l2_loss(weights1) + tf.nn.l2_loss(weights2) +
tf.nn.l2_loss(weights3) + tf.nn.l2_loss(weights4))
# optimizer
global_step = tf.Variable(0)
learning_rate = tf.train.exponential_decay(initial_learning_rate,global_step,update_steps,update_exponent)
optimizer = tf.train.AdamOptimizer(learning_rate).minimize(loss,global_step=global_step)
# Predictions for the training, validation, and test data.
test_prediction = tf.nn.softmax(forwardPropwithoutDrop(tf_test_dataset))
valid_prediction = tf.nn.softmax(forwardPropwithoutDrop(tf_valid_dataset))
train_prediction = tf.nn.softmax(forwardPropwithoutDrop(tf_train_dataset))
In [13]:
with tf.Session(graph=dnnGraph) as session:
tf.initialize_all_variables().run()
print("Initialized")
for step in range(num_steps):
# Pick an offset within the training data, which has been randomized.
# Note: we could use better randomization across epochs.
offset = (step*batch_size)%(train_subset-batch_size)
# Generate a minibatch.
batch_data = train_dataset[offset:(offset+batch_size),:]
batch_labels = train_labels[offset:(offset+batch_size),:]
# Prepare a dictionary telling the session where to feed the minibatch.
# The key of the dictionary is the placeholder node of the graph to be fed,
# and the value is the numpy array to feed to it.
feed_dict = {tf_train_dataset:batch_data,tf_train_labels:batch_labels}
_, l, predictions = session.run([optimizer, loss, train_prediction], feed_dict=feed_dict)
if (step%500 == 0):
print("Minibatch loss at step %d: %f" % (step, l))
print("Minibatch accuracy: %.1f%%" % accuracy(predictions, batch_labels))
print("Validation accuracy: %.1f%%" % accuracy(valid_prediction.eval(), valid_labels))
print("Test accuracy: %.1f%%" % accuracy(test_prediction.eval(), test_labels))
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