def get_output_for(self, input, **kwargs):
num_feature_maps = input.shape[self.axis]
num_pools = num_feature_maps // self.pool_size
pool_shape = ()
arange_shuffle_pattern = ()
for k in range(self.axis):
pool_shape += (input.shape[k],)
arange_shuffle_pattern += ('x',)
pool_shape += (num_pools, self.pool_size)
arange_shuffle_pattern += ('x', 0)
for k in range(self.axis + 1, input.ndim):
pool_shape += (input.shape[k],)
arange_shuffle_pattern += ('x',)
input_reshaped = input.reshape(pool_shape)
max_indices = T.argmax(input_reshaped, axis=self.axis + 1,
keepdims=True)
arange = T.arange(self.pool_size).dimshuffle(*arange_shuffle_pattern)
mask = T.eq(max_indices, arange).reshape(input.shape)
return input * mask
def main(model='mlp', num_epochs=500):
# Load the dataset
print("Loading data...")
X_train, y_train, X_val, y_val, X_test, y_test = load_dataset()
# Prepare Theano variables for inputs and targets
input_var = T.tensor4('inputs', fixed_shape=(128,) + X_train.shape[1:])
target_var = T.ivector('targets')
# Create neural network model (depending on first command line parameter)
print("Building model and compiling functions...")
if model == 'mlp':
network = build_mlp(input_var)
elif model.startswith('custom_mlp:'):
depth, width, drop_in, drop_hid = model.split(':', 1)[1].split(',')
network = build_custom_mlp(input_var, int(depth), int(width),
float(drop_in), float(drop_hid))
elif model == 'cnn':
network = build_cnn(input_var)
else:
print("Unrecognized model type %r." % model)
return
# Create a loss expression for training, i.e., a scalar objective we want
# to minimize (for our multi-class problem, it is the cross-entropy loss):
prediction = lasagne.layers.get_output(network)
loss = lasagne.objectives.categorical_crossentropy(prediction, target_var)
loss = T.mean(loss)
# We could add some weight decay as well here, see lasagne.regularization.
# Create update expressions for training, i.e., how to modify the
# parameters at each training step. Here, we'll use Stochastic Gradient
# Descent (SGD) with Nesterov momentum, but Lasagne offers plenty more.
params = lasagne.layers.get_all_params(network, trainable=True)
updates = lasagne.updates.nesterov_momentum(
loss, params, learning_rate=0.01, momentum=0.9)
# Create a loss expression for validation/testing. The crucial difference
# here is that we do a deterministic forward pass through the network,
# disabling dropout layers.
test_prediction = lasagne.layers.get_output(network, deterministic=True)
test_loss = lasagne.objectives.categorical_crossentropy(test_prediction,
target_var)
test_loss = T.mean(test_loss)
# As a bonus, also create an expression for the classification accuracy:
test_acc = T.mean(T.cast(T.eq(
T.cast(T.argmax(test_prediction, axis=1), 'int32'),
T.cast(target_var, 'int32')
), theano.config.floatX))
# Compile a function performing a training step on a mini-batch (by giving
# the updates dictionary) and returning the corresponding training loss:
train_fn = theano.function([input_var, target_var], loss, updates=updates)
# Compile a second function computing the validation loss and accuracy:
val_fn = theano.function([input_var, target_var], [test_loss, test_acc])
# Finally, launch the training loop.
print("Starting training...")
# We iterate over epochs:
for epoch in range(num_epochs):
# In each epoch, we do a full pass over the training data:
train_err = 0
train_batches = 0
start_time = time.time()
for batch in iterate_minibatches(X_train, y_train, 128, shuffle=True):
inputs, targets = batch
train_err += train_fn(inputs, targets)
train_batches += 1
# And a full pass over the validation data:
val_err = 0
val_acc = 0
val_batches = 0
for batch in iterate_minibatches(X_val, y_val, 128, shuffle=False):
inputs, targets = batch
err, acc = val_fn(inputs, targets)
val_err += err
val_acc += acc
val_batches += 1
# Then we print the results for this epoch:
print("Epoch {} of {} took {:.3f}s".format(
epoch + 1, num_epochs, time.time() - start_time))
print(" training loss:\t\t{:.6f}".format(train_err / train_batches))
print(" validation loss:\t\t{:.6f}".format(val_err / val_batches))
print(" validation accuracy:\t\t{:.2f} %".format(
val_acc / val_batches * 100))
# After training, we compute and print the test error:
test_err = 0
test_acc = 0
test_batches = 0
for batch in iterate_minibatches(X_test, y_test, 128, shuffle=False):
inputs, targets = batch
err, acc = val_fn(inputs, targets)
test_err += err
test_acc += acc
test_batches += 1
print("Final results:")
print(" test loss:\t\t\t{:.6f}".format(test_err / test_batches))
print(" test accuracy:\t\t{:.2f} %".format(
test_acc / test_batches * 100))
