Las redes de autoencoder parecen ser mucho más difíciles que las redes MLP clasificadoras normales. Después de varios intentos de usar Lasagne, todo lo que obtengo en la salida reconstruida es algo que se asemeja en su mejor momento a un promedio borroso de todas las imágenes de la base de datos MNIST sin distinción sobre cuál es realmente el dígito de entrada.
La estructura de redes que elegí son las siguientes capas en cascada:
- capa de entrada (28x28)
- Capa convolucional 2D, tamaño de filtro 7x7
- Capa de agrupación máxima, tamaño 3x3, zancada 2x2
- Capa de aplanamiento densa (totalmente conectada), 10 unidades (este es el cuello de botella)
- Capa densa (totalmente conectada), 121 unidades
- Reformar la capa a 11x11
- Capa convolucional 2D, tamaño de filtro 3x3
- Factor de capa de escalado 2D 2
- Capa convolucional 2D, tamaño de filtro 3x3
- Factor de capa de escalado 2D 2
- Capa convolucional 2D, tamaño de filtro 5x5
- Función de agrupación máxima (de 31x28x28 a 28x28)
Todas las capas convolucionales 2D tienen los sesgos desatados, activaciones sigmoideas y 31 filtros.
Todas las capas completamente conectadas tienen activaciones sigmoideas.
La función de pérdida utilizada es error cuadrado , la función de actualización es adagrad. La longitud del fragmento para el aprendizaje es de 100 muestras, multiplicadas por 1000 épocas.
La siguiente es una ilustración del problema: la fila superior son algunas muestras configuradas como entradas de la red, la fila inferior es la reconstrucción:
Solo para completar, el siguiente es el código que utilicé:
import theano.tensor as T
import theano
import sys
sys.path.insert(0,'./Lasagne') # local checkout of Lasagne
import lasagne
from theano import pp
from theano import function
import gzip
import numpy as np
from sklearn.preprocessing import OneHotEncoder
import matplotlib.pyplot as plt
def load_mnist():
def load_mnist_images(filename):
with gzip.open(filename, 'rb') as f:
data = np.frombuffer(f.read(), np.uint8, offset=16)
# The inputs are vectors now, we reshape them to monochrome 2D images,
# following the shape convention: (examples, channels, rows, columns)
data = data.reshape(-1, 1, 28, 28)
# The inputs come as bytes, we convert them to float32 in range [0,1].
# (Actually to range [0, 255/256], for compatibility to the version
# provided at http://deeplearning.net/data/mnist/mnist.pkl.gz.)
return data / np.float32(256)
def load_mnist_labels(filename):
# Read the labels in Yann LeCun's binary format.
with gzip.open(filename, 'rb') as f:
data = np.frombuffer(f.read(), np.uint8, offset=8)
# The labels are vectors of integers now, that's exactly what we want.
return data
X_train = load_mnist_images('train-images-idx3-ubyte.gz')
y_train = load_mnist_labels('train-labels-idx1-ubyte.gz')
X_test = load_mnist_images('t10k-images-idx3-ubyte.gz')
y_test = load_mnist_labels('t10k-labels-idx1-ubyte.gz')
return X_train, y_train, X_test, y_test
def plot_filters(conv_layer):
W = conv_layer.get_params()[0]
W_fn = theano.function([],W)
params = W_fn()
ks = np.squeeze(params)
kstack = np.vstack(ks)
plt.imshow(kstack,interpolation='none')
plt.show()
def main():
#theano.config.exception_verbosity="high"
#theano.config.optimizer='None'
X_train, y_train, X_test, y_test = load_mnist()
ohe = OneHotEncoder()
y_train = ohe.fit_transform(np.expand_dims(y_train,1)).toarray()
chunk_len = 100
visamount = 10
num_epochs = 1000
num_filters=31
dropout_p=.0
print "X_train.shape",X_train.shape,"y_train.shape",y_train.shape
input_var = T.tensor4('X')
output_var = T.tensor4('X')
conv_nonlinearity = lasagne.nonlinearities.sigmoid
net = lasagne.layers.InputLayer((chunk_len,1,28,28), input_var)
conv1 = net = lasagne.layers.Conv2DLayer(net,num_filters,(7,7),nonlinearity=conv_nonlinearity,untie_biases=True)
net = lasagne.layers.MaxPool2DLayer(net,(3,3),stride=(2,2))
net = lasagne.layers.DropoutLayer(net,p=dropout_p)
#conv2_layer = lasagne.layers.Conv2DLayer(dropout_layer,num_filters,(3,3),nonlinearity=conv_nonlinearity)
#pool2_layer = lasagne.layers.MaxPool2DLayer(conv2_layer,(3,3),stride=(2,2))
net = lasagne.layers.DenseLayer(net,10,nonlinearity=lasagne.nonlinearities.sigmoid)
#augment_layer1 = lasagne.layers.DenseLayer(reduction_layer,33,nonlinearity=lasagne.nonlinearities.sigmoid)
net = lasagne.layers.DenseLayer(net,121,nonlinearity=lasagne.nonlinearities.sigmoid)
net = lasagne.layers.ReshapeLayer(net,(chunk_len,1,11,11))
net = lasagne.layers.Conv2DLayer(net,num_filters,(3,3),nonlinearity=conv_nonlinearity,untie_biases=True)
net = lasagne.layers.Upscale2DLayer(net,2)
net = lasagne.layers.Conv2DLayer(net,num_filters,(3,3),nonlinearity=conv_nonlinearity,untie_biases=True)
#pool_after0 = lasagne.layers.MaxPool2DLayer(conv_after1,(3,3),stride=(2,2))
net = lasagne.layers.Upscale2DLayer(net,2)
net = lasagne.layers.DropoutLayer(net,p=dropout_p)
#conv_after2 = lasagne.layers.Conv2DLayer(upscale_layer1,num_filters,(3,3),nonlinearity=conv_nonlinearity,untie_biases=True)
#pool_after1 = lasagne.layers.MaxPool2DLayer(conv_after2,(3,3),stride=(1,1))
#upscale_layer2 = lasagne.layers.Upscale2DLayer(pool_after1,4)
net = lasagne.layers.Conv2DLayer(net,num_filters,(5,5),nonlinearity=conv_nonlinearity,untie_biases=True)
net = lasagne.layers.FeaturePoolLayer(net,num_filters,pool_function=theano.tensor.max)
print "output_shape:",lasagne.layers.get_output_shape(net)
params = lasagne.layers.get_all_params(net, trainable=True)
prediction = lasagne.layers.get_output(net)
loss = lasagne.objectives.squared_error(prediction, output_var)
#loss = lasagne.objectives.binary_crossentropy(prediction, output_var)
aggregated_loss = lasagne.objectives.aggregate(loss)
updates = lasagne.updates.adagrad(aggregated_loss,params)
train_fn = theano.function([input_var, output_var], loss, updates=updates)
test_prediction = lasagne.layers.get_output(net, deterministic=True)
predict_fn = theano.function([input_var], test_prediction)
print "starting training..."
for epoch in range(num_epochs):
selected = list(set(np.random.random_integers(0,59999,chunk_len*4)))[:chunk_len]
X_train_sub = X_train[selected,:]
_loss = train_fn(X_train_sub, X_train_sub)
print("Epoch %d: Loss %g" % (epoch + 1, np.sum(_loss) / len(X_train)))
"""
chunk = X_train[0:chunk_len,:,:,:]
result = predict_fn(chunk)
vis1 = np.hstack([chunk[j,0,:,:] for j in range(visamount)])
vis2 = np.hstack([result[j,0,:,:] for j in range(visamount)])
plt.imshow(np.vstack([vis1,vis2]))
plt.show()
"""
print "done."
chunk = X_train[0:chunk_len,:,:,:]
result = predict_fn(chunk)
print "chunk.shape",chunk.shape
print "result.shape",result.shape
plot_filters(conv1)
for i in range(chunk_len/visamount):
vis1 = np.hstack([chunk[i*visamount+j,0,:,:] for j in range(visamount)])
vis2 = np.hstack([result[i*visamount+j,0,:,:] for j in range(visamount)])
plt.imshow(np.vstack([vis1,vis2]))
plt.show()
import ipdb; ipdb.set_trace()
if __name__ == "__main__":
main()¿Alguna idea sobre cómo mejorar esta red para obtener un autoencoder que funcione razonablemente?
¡Problema resuelto!
Con una implementación que es bastante diferente, usando un rectificador con fugas en lugar de una función sigmoidea en las capas convolucionales, solo 2 (!!) nodos en la capa de cuello de botella y convoluciones con núcleos 1x1 al final.
Aquí está el resultado de alguna reconstrucción:
Código:
import theano.tensor as T
import theano
import sys
sys.path.insert(0,'./Lasagne') # local checkout of Lasagne
import lasagne
from theano import pp
from theano import function
import theano.tensor.nnet
import gzip
import numpy as np
from sklearn.preprocessing import OneHotEncoder
import matplotlib.pyplot as plt
def load_mnist():
def load_mnist_images(filename):
with gzip.open(filename, 'rb') as f:
data = np.frombuffer(f.read(), np.uint8, offset=16)
# The inputs are vectors now, we reshape them to monochrome 2D images,
# following the shape convention: (examples, channels, rows, columns)
data = data.reshape(-1, 1, 28, 28)
# The inputs come as bytes, we convert them to float32 in range [0,1].
# (Actually to range [0, 255/256], for compatibility to the version
# provided at http://deeplearning.net/data/mnist/mnist.pkl.gz.)
return data / np.float32(256)
def load_mnist_labels(filename):
# Read the labels in Yann LeCun's binary format.
with gzip.open(filename, 'rb') as f:
data = np.frombuffer(f.read(), np.uint8, offset=8)
# The labels are vectors of integers now, that's exactly what we want.
return data
X_train = load_mnist_images('train-images-idx3-ubyte.gz')
y_train = load_mnist_labels('train-labels-idx1-ubyte.gz')
X_test = load_mnist_images('t10k-images-idx3-ubyte.gz')
y_test = load_mnist_labels('t10k-labels-idx1-ubyte.gz')
return X_train, y_train, X_test, y_test
def main():
X_train, y_train, X_test, y_test = load_mnist()
ohe = OneHotEncoder()
y_train = ohe.fit_transform(np.expand_dims(y_train,1)).toarray()
chunk_len = 100
num_epochs = 10000
num_filters=7
input_var = T.tensor4('X')
output_var = T.tensor4('X')
#conv_nonlinearity = lasagne.nonlinearities.sigmoid
#conv_nonlinearity = lasagne.nonlinearities.rectify
conv_nonlinearity = lasagne.nonlinearities.LeakyRectify(.1)
softplus = theano.tensor.nnet.softplus
#conv_nonlinearity = theano.tensor.nnet.softplus
net = lasagne.layers.InputLayer((chunk_len,1,28,28), input_var)
conv1 = net = lasagne.layers.Conv2DLayer(net,num_filters,(7,7),nonlinearity=conv_nonlinearity,untie_biases=True)
net = lasagne.layers.MaxPool2DLayer(net,(3,3),stride=(2,2))
net = lasagne.layers.DenseLayer(net,2,nonlinearity=lasagne.nonlinearities.sigmoid)
net = lasagne.layers.DenseLayer(net,49,nonlinearity=lasagne.nonlinearities.sigmoid)
net = lasagne.layers.ReshapeLayer(net,(chunk_len,1,7,7))
net = lasagne.layers.Conv2DLayer(net,num_filters,(3,3),nonlinearity=conv_nonlinearity,untie_biases=True)
net = lasagne.layers.MaxPool2DLayer(net,(3,3),stride=(1,1))
net = lasagne.layers.Upscale2DLayer(net,4)
net = lasagne.layers.Conv2DLayer(net,num_filters,(3,3),nonlinearity=conv_nonlinearity,untie_biases=True)
net = lasagne.layers.MaxPool2DLayer(net,(3,3),stride=(1,1))
net = lasagne.layers.Upscale2DLayer(net,4)
net = lasagne.layers.Conv2DLayer(net,num_filters,(5,5),nonlinearity=conv_nonlinearity,untie_biases=True)
net = lasagne.layers.Conv2DLayer(net,num_filters,(1,1),nonlinearity=conv_nonlinearity,untie_biases=True)
net = lasagne.layers.FeaturePoolLayer(net,num_filters,pool_function=theano.tensor.max)
net = lasagne.layers.Conv2DLayer(net,1,(1,1),nonlinearity=conv_nonlinearity,untie_biases=True)
print "output shape:",net.output_shape
params = lasagne.layers.get_all_params(net, trainable=True)
prediction = lasagne.layers.get_output(net)
loss = lasagne.objectives.squared_error(prediction, output_var)
#loss = lasagne.objectives.binary_hinge_loss(prediction, output_var)
aggregated_loss = lasagne.objectives.aggregate(loss)
#updates = lasagne.updates.adagrad(aggregated_loss,params)
updates = lasagne.updates.nesterov_momentum(aggregated_loss,params,0.5)#.005
train_fn = theano.function([input_var, output_var], loss, updates=updates)
test_prediction = lasagne.layers.get_output(net, deterministic=True)
predict_fn = theano.function([input_var], test_prediction)
print "starting training..."
for epoch in range(num_epochs):
selected = list(set(np.random.random_integers(0,59999,chunk_len*4)))[:chunk_len]
X_train_sub = X_train[selected,:]
_loss = train_fn(X_train_sub, X_train_sub)
print("Epoch %d: Loss %g" % (epoch + 1, np.sum(_loss) / len(X_train)))
print "done."
chunk = X_train[0:chunk_len,:,:,:]
result = predict_fn(chunk)
print "chunk.shape",chunk.shape
print "result.shape",result.shape
visamount = 10
for i in range(10):
vis1 = np.hstack([chunk[i*visamount+j,0,:,:] for j in range(visamount)])
vis2 = np.hstack([result[i*visamount+j,0,:,:] for j in range(visamount)])
plt.imshow(np.vstack([vis1,vis2]))
plt.show()
import ipdb; ipdb.set_trace()
if __name__ == "__main__":
main()
