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我已經構建了一個ResNet模型，其中tensorflow用於對MNIST數字進行分類。然而，在訓練時間，我的準確度沒有太大的變化，即使在3-4個時期後，我的準確率也保持在0.1左右，這對應於隨機分類器（1次超過10來做出正確的預測）。準確性不會在MNIST數據集的ResNet中增加
我曾嘗試更改激活函數（relu to sigmoid），但它不提高準確性。修改學習率沒有顯着影響。我想知道
是否我get_variable（）的調用是正確的....以下是完整的模式：
import tensorflow as tf
import numpy as np
import matplotlib.pyplot as plt
def conv_2D(x, w, b, stride=1, padding='SAME', activation=None):
'''
2D convolution
x: tensor of shape (batch, height, width, channel) ->
w: tensor of shape (f_width, f_height, channels_in, channels_out) -> weights
b: tensor of shape (channels_out) -> biases
'''
# convolution
x = tf.nn.conv2d(x, w, strides=[1, stride, stride, 1], padding=padding)
# add biases
x = tf.nn.bias_add(x, b)
if activation is not None:
x = activation(x)
return x
def print_tensor_shape(x, msg=''):
print(msg, x.get_shape().as_list())
class RepBlock(object):
def __init__(self, num_repeats, num_filters, bottleneck_size, name_scope):
self.num_repeats = num_repeats
self.num_filters = num_filters
self.bottleneck_size = bottleneck_size
self.name_scope = name_scope
def apply_block(self, net):
print_tensor_shape(net, 'entering apply_block')
# loop over repeats
for i_repeat in range(self.num_repeats):
print_tensor_shape(net, 'layer %i' % i_repeat)
# subsampling is performed by a convolution with stride=2, only
# for the first convolution of the first repetition
if i_repeat == 0:
stride = 2
else:
stride = 1
name = self.name_scope+'/%i/conv_in' % i_repeat
with tf.variable_scope(name):
w = tf.get_variable('w', initializer=tf.random_normal([1, 1, net.get_shape().as_list()[-1], self.bottleneck_size]))
b = tf.get_variable('b', initializer=tf.random_normal([self.bottleneck_size]))
conv = conv_2D(net, w, b, stride=stride, padding='VALID', activation=tf.nn.relu)
print_tensor_shape(conv, name)
name = self.name_scope+'/%i/conv_bottleneck' % i_repeat
with tf.variable_scope(name):
w = tf.get_variable('w', initializer=tf.random_normal([3, 3, conv.get_shape().as_list()[-1], self.bottleneck_size]))
b = tf.get_variable('b', initializer=tf.random_normal([self.bottleneck_size]))
conv = conv_2D(conv, w, b, stride=1, padding='SAME', activation=tf.nn.relu)
print_tensor_shape(conv, name)
name = self.name_scope+'/%i/conv_out' % i_repeat
with tf.variable_scope(name):
w = tf.get_variable('w', initializer=tf.random_normal([1, 1, conv.get_shape().as_list()[-1], self.num_filters]))
b = tf.get_variable('b', initializer=tf.random_normal([self.num_filters]))
conv = conv_2D(conv, w, b, stride=1, padding='VALID', activation=None)
print_tensor_shape(conv, name)
if i_repeat == 0:
net = conv + tf.nn.max_pool(net, ksize=[1, 2, 2, 1], strides=[1, 2, 2, 1], padding='SAME')
else:
net = conv + net
net = tf.nn.relu(net)
return net
def resnet(x):
# reshape input
x = tf.reshape(x, shape=[-1, 28, 28, 1])
# init block for each layer
layer_1 = RepBlock(num_repeats=3, num_filters=128, bottleneck_size=32, name_scope='layer_1')
layer_2 = RepBlock(num_repeats=3, num_filters=256, bottleneck_size=64, name_scope='layer_2')
# layer_3 = RepBlock(num_repeats=3, num_filters=512, bottleneck_size=128, name_scope='layer_3')
# layer_4 = RepBlock(num_repeats=3, num_filters=1024, bottleneck_size=256, name_scope='layer_4')
layers = [layer_1, layer_2]
# first layer
name = 'conv_1'
with tf.variable_scope(name):
w = tf.get_variable('w', initializer=tf.random_normal([7, 7, x.get_shape().as_list()[-1], 64]))
b = tf.get_variable('b', initializer=tf.random_normal([64]))
net = conv_2D(x, w, b, stride=1, padding='SAME', activation=tf.nn.relu)
print_tensor_shape(net)
net = tf.nn.max_pool(
net, [1, 3, 3, 1], strides=[1, 2, 2, 1], padding='SAME')
print_tensor_shape(net)
with tf.variable_scope('conv_2'):
w = tf.get_variable('w', initializer=tf.random_normal([1, 1, net.get_shape().as_list()[-1], layers[0].num_filters]))
b = tf.get_variable('b', initializer=tf.random_normal([layers[0].num_filters]))
net = conv_2D(net, w, b, stride=1, padding='SAME', activation=tf.nn.relu)
print_tensor_shape(net)
for i_layer, layer in enumerate(layers):
# pass the net through all blocks of the layer
net = layer.apply_block(net)
print_tensor_shape(net, 'After block')
try:
# upscale (depth) to the next block size
next_block = layers[i_layer+1]
with tf.variable_scope('upscale_%i' % i_layer):
w = tf.get_variable('w', initializer=tf.random_normal([1, 1, net.get_shape().as_list()[-1], next_block.num_filters]))
b = tf.get_variable('b', initializer=tf.random_normal([next_block.num_filters]))
net = conv_2D(net, w, b, stride=1, padding='SAME', activation=tf.nn.relu)
print_tensor_shape(net)
except IndexError:
pass
# apply average pooling
net = tf.nn.avg_pool(net, ksize=[1, net.get_shape().as_list()[1], net.get_shape().as_list()[2], 1],
strides=[1, 1, 1, 1], padding='VALID')
print_tensor_shape(net, msg='after average pooling')
# fully connected layer
with tf.variable_scope('fc'):
w = tf.get_variable('w', initializer=tf.random_normal([256, 10]))
b = tf.get_variable('b', initializer=tf.random_normal([10]))
net = tf.reshape(net, shape=[-1, 256])
net = tf.add(tf.matmul(net, w), b)
print_tensor_shape(net, 'after fc')
return net
if __name__ == '__main__':
from tensorflow.examples.tutorials.mnist import input_data
mnist = input_data.read_data_sets("MNIST_data/", one_hot=True)
X = tf.placeholder(tf.float32, [None, 784])
Y = tf.placeholder(tf.float32, [None, 10])
Y_pred = resnet(X)
cost = tf.reduce_mean(tf.nn.softmax_cross_entropy_with_logits(logits=Y_pred, labels=Y))
optim = tf.train.AdamOptimizer(learning_rate=0.01).minimize(cost)
correct_pred = tf.equal(tf.argmax(Y_pred, 1), tf.argmax(Y, 1))
accuracy = tf.reduce_mean(tf.cast(correct_pred, tf.float32))
session = tf.InteractiveSession()
init_op = tf.initialize_all_variables()
session.run(init_op)
nb_epochs = 10
batch_size = 128
training_size = mnist.train.num_examples
nb_mini_batches = training_size // batch_size
# loop over epochs
for i_epoch in range(nb_epochs):
# loop over mini-batches
for i_batch in range(nb_mini_batches):
# get mini-batch
batch_x, batch_y = mnist.train.next_batch(batch_size)
[_, cost_val, acc] = session.run([optim, cost, accuracy], feed_dict={X: batch_x, Y:batch_y})
print('epoch %i - batch %i - cost=%f - accuracy=%f' % (i_epoch, i_batch, cost_val, acc))