Я пишу классификатор нейронной сети в TensorFlow/Python для набора данных notMNIST. Я реализовал l2-регуляризацию и исключение из скрытых слоев. Он работает нормально, пока есть только один скрытый слой, но когда я добавил больше слоев (для повышения точности), функция потерь быстро растет на каждом шаге, становясь NaN на шаге 5. Я попытался временно отключить регуляцию выпадения и L2, но Я получаю такое же поведение, пока существуют слои 2+. Я даже переписал свой код с нуля (делая некоторые рефакторинг, чтобы сделать его более гибким), но с теми же результатами. Количество и размер слоев контролируется hidden_layer_spec
. Что мне не хватает?
#works for np.array([1024]) with about 96.1% accuracy
hidden_layer_spec = np.array([1024, 300])
num_hidden_layers = hidden_layer_spec.shape[0]
batch_size = 256
beta = 0.0005
epochs = 100
stepsPerEpoch = float(train_dataset.shape[0]) / batch_size
num_steps = int(math.ceil(float(epochs) * stepsPerEpoch))
l2Graph = tf.Graph()
with l2Graph.as_default():
#with tf.device('/cpu:0'):
# Input data. For the training data, we use a placeholder that will be fed
# at run time with a training minibatch.
tf_train_dataset = tf.placeholder(tf.float32,
shape=(batch_size, image_size * image_size))
tf_train_labels = tf.placeholder(tf.float32, shape=(batch_size, num_labels))
tf_valid_dataset = tf.constant(valid_dataset)
tf_test_dataset = tf.constant(test_dataset)
weights = []
biases = []
for hi in range(0, num_hidden_layers + 1):
width = image_size * image_size if hi == 0 else hidden_layer_spec[hi - 1]
height = num_labels if hi == num_hidden_layers else hidden_layer_spec[hi]
weights.append(tf.Variable(tf.truncated_normal([width, height]), name = "w" + 'hi + 1'))
biases.append(tf.Variable(tf.zeros([height]), name = "b" + 'hi + 1'))
print('width' + 'x' + 'height')
def logits(input, addDropoutLayer = False):
previous_layer = input
for hi in range(0, hidden_layer_spec.shape[0]):
previous_layer = tf.nn.relu(tf.matmul(previous_layer, weights[hi]) + biases[hi])
if addDropoutLayer:
previous_layer = tf.nn.dropout(previous_layer, 0.5)
return tf.matmul(previous_layer, weights[num_hidden_layers]) + biases[num_hidden_layers]
# Training computation.
train_logits = logits(tf_train_dataset, True)
l2 = tf.nn.l2_loss(weights[0])
for hi in range(1, len(weights)):
l2 = l2 + tf.nn.l2_loss(weights[0])
loss = tf.reduce_mean(tf.nn.softmax_cross_entropy_with_logits(train_logits, tf_train_labels)) + beta * l2
# Optimizer.
global_step = tf.Variable(0) # count the number of steps taken.
learning_rate = tf.train.exponential_decay(0.5, global_step, int(stepsPerEpoch) * 2, 0.96, staircase = True)
optimizer = tf.train.GradientDescentOptimizer(learning_rate).minimize(loss, global_step=global_step)
# Predictions for the training, validation, and test data.
train_prediction = tf.nn.softmax(train_logits)
valid_prediction = tf.nn.softmax(logits(tf_valid_dataset))
test_prediction = tf.nn.softmax(logits(tf_test_dataset))
saver = tf.train.Saver()
with tf.Session(graph=l2Graph) 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("Learning rate: " % learning_rate)
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))
save_path = saver.save(session, "l2_degrade.ckpt")
print("Model save to " + 'save_path')