[英]VGG16 Keras fine tuning: low accuracy
I've already asked similar question here , but now I have slightly different problem, therefore asking new question. 我已经在这里问了类似的问题,但现在我的问题略有不同,因此提出了新问题。
I decided to use slightly different approach instead of proposed among answers in the referenced question to train, and then fine-tune model. 我决定使用稍微不同的方法而不是在引用的问题中的答案中提出训练,然后微调模型。
Update : I've replaced old question provided here with more suitable version
更新 :我已经用更合适的版本替换了这里提供的旧问题
Here is my sequence of actions: 这是我的一系列行动:
And here is a code I use to implement aforementioned sequence of actions: 这是我用来实现上述动作序列的代码:
import warnings
warnings.simplefilter('ignore', UserWarning)
warnings.simplefilter('ignore', DeprecationWarning)
from __future__ import print_function
from itertools import izip_longest as zip_longest
from pprint import pformat as pf
from pprint import pprint as pp
import os
from keras.preprocessing.image import ImageDataGenerator, array_to_img, img_to_array, load_img
from keras.layers import Conv2D, MaxPooling2D, MaxPooling2D, ZeroPadding2D
from keras.layers import Dropout, Flatten, Dense, InputLayer, Lambda
from keras.models import Sequential, Model, load_model
from keras.utils.data_utils import get_file
from keras.optimizers import SGD
import keras.backend as K
import numpy as np
RANDOM_STATE = 1
IMAGE_WIDTH = 224
IMAGE_HEIGHT = 224
BATCH_SIZE = 4
VGG_MEAN = np.array([123.68, 116.779, 103.939]).reshape((3, 1, 1))
VGG16_WEIGHTS_PATH = 'http://www.platform.ai/models/vgg16.h5'
DATA_ROOT = os.path.join(os.path.expanduser('~'), 'data', 'dogscats')
TRAIN_DIR = os.path.join(DATA_ROOT, 'train')
VALID_DIR = os.path.join(DATA_ROOT, 'valid')
SAMPLES_DIR = os.path.expanduser('~/dogscats_samples')
np.random.seed(RANDOM_STATE)
K.set_image_dim_ordering('th')
def get_batches(dirname, gen=ImageDataGenerator(), shuffle=True,
batch_size=BATCH_SIZE, class_mode='categorical'):
return gen.flow_from_directory(
os.path.join(SAMPLES_DIR, dirname),
target_size=(IMAGE_WIDTH, IMAGE_HEIGHT),
class_mode=class_mode,
shuffle=shuffle,
batch_size=batch_size)
def vgg_preprocess(x):
x = x - VGG_MEAN
return x[:, ::-1]
def conv_block(model, n_layers, n_filters, name='block'):
for i in range(n_layers):
model.add(ZeroPadding2D((1, 1), name='%s_padding_%s' % (name, i)))
model.add(Conv2D(n_filters, (3, 3), activation='relu', name='%s_conv2d_%s' % (name, i)))
model.add(MaxPooling2D((2, 2), strides=(2, 2), name='%s_maxpool' % name))
def fc_block(model, name='block'):
model.add(Dense(4096, activation='relu', name=name + '_dense'))
model.add(Dropout(0.5))
def build_vgg_16():
model = Sequential()
input_shape = (3, IMAGE_WIDTH, IMAGE_HEIGHT)
model.add(InputLayer(input_shape=input_shape))
model.add(Lambda(vgg_preprocess))
conv_block(model, n_layers=2, n_filters=64, name='block1')
conv_block(model, n_layers=2, n_filters=128, name='block2')
conv_block(model, n_layers=3, n_filters=256, name='block3')
conv_block(model, n_layers=3, n_filters=512, name='block4')
conv_block(model, n_layers=3, n_filters=512, name='block5')
model.add(Flatten())
fc_block(model)
fc_block(model)
model.add(Dense(1000, activation='softmax'))
return model
def train_finetuned_model():
file_path = get_file('vgg16.h5', VGG16_WEIGHTS_PATH, cache_subdir='models')
print('Building VGG16 (no-top) model to generate bottleneck features')
vgg16_notop = build_vgg_16()
vgg16_notop.load_weights(file_path)
for _ in range(6):
vgg16_notop.pop()
vgg16_notop.compile(optimizer='rmsprop', loss='categorical_crossentropy', metrics=['accuracy'])
train_batches = get_batches('train', shuffle=False, class_mode=None)
train_labels = np.array([0]*1000 + [1]*1000)
bottleneck_train = vgg16_notop.predict_generator(train_batches, steps=2000 // BATCH_SIZE)
valid_batches = get_batches('valid', shuffle=False, class_mode=None)
valid_labels = np.array([0]*400 + [1]*400)
bottleneck_valid = vgg16_notop.predict_generator(valid_batches, steps=800 // BATCH_SIZE)
print('Training top model on bottleneck features')
top_model = Sequential()
top_model.add(Flatten(input_shape=bottleneck_train.shape[1:]))
top_model.add(Dense(256, activation='relu'))
top_model.add(Dropout(0.5))
top_model.add(Dense(1, activation='sigmoid'))
top_model.compile(optimizer='rmsprop', loss='binary_crossentropy', metrics=['accuracy'])
top_model.fit(bottleneck_train, train_labels,
batch_size=32, epochs=50,
validation_data=(bottleneck_valid, valid_labels))
print('Concatenate new VGG16 (without top layer) with pretrained top model')
vgg16_fine = build_vgg_16()
vgg16_fine.load_weights(file_path)
for _ in range(6):
vgg16_fine.pop()
vgg16_fine.add(Flatten(name='top_flatten'))
vgg16_fine.add(Dense(256, activation='relu', name='top_dense'))
vgg16_fine.add(Dropout(0.5, name='top_dropout'))
vgg16_fine.add(Dense(1, activation='sigmoid', name='top_sigmoid'))
for i, layer in enumerate(reversed(top_model.layers), 1):
pretrained_weights = layer.get_weights()
vgg16_fine.layers[-i].set_weights(pretrained_weights)
for layer in vgg16_fine.layers[:26]:
layer.trainable = False
vgg16_fine.compile(optimizer=SGD(lr=1e-4, momentum=0.9),
loss='binary_crossentropy',
metrics=['accuracy'])
print('Train concatenated model on dogs/cats dataset sample')
train_datagen = ImageDataGenerator(rescale=1./255,
shear_range=0.2,
zoom_range=0.2,
horizontal_flip=True)
test_datagen = ImageDataGenerator(rescale=1./255)
train_batches = get_batches('train', gen=train_datagen, class_mode='binary')
valid_batches = get_batches('valid', gen=test_datagen, class_mode='binary')
vgg16_fine.fit_generator(train_batches,
steps_per_epoch=2000 // BATCH_SIZE,
epochs=50,
validation_data=valid_batches,
validation_steps=800 // BATCH_SIZE)
return vgg16_fine
final_model = train_finetuned_model()
But the problem is that model's accuracy drastically dropped. 但问题是模型的准确性急剧下降。 After 50 epochs, its accuracy is around
50%
. 经过50个时代,其准确率约为
50%
。 Therefore, probably I've done something wrong. 因此,我可能做错了什么。
Maybe something wrong with parameters, ie learning rate, batch size, etc.? 参数可能有问题,即学习率,批量大小等?
Your fully connected layers look totally different from the original VGG architecture. 完全连接的层看起来与原始VGG架构完全不同。
# yours
Flatten()
Dense(256, activation='relu')
Dense(1, activation='sigmoid')
# original
Flatten()
Dense(4096, activation='relu')
Dense(4096, activation='relu')
Dense(2, activation='softmax')
Two points. 两点。
The last layer should be 2-class-softmax instead of sigmoid. 最后一层应该是2级 - softmax而不是sigmoid。 The accuracy is not computed as you expect if you use sigmoid, I guess.
如果你使用sigmoid,我猜你的准确度不会像你期望的那样计算。
Complexity (number of neurons and layers) seems to be too low. 复杂性(神经元和层数)似乎太低。
Well, not sure if it is a right solution, but I was able to increase accuracy at least up to 70% with this code (probably the main reason is decreased learning rate and more epochs): 好吧,不确定它是否是一个正确的解决方案,但我能够使用此代码将准确性提高至少70%(可能主要原因是降低学习率和更多时期):
def train_finetuned_model(lr=1e-5, verbose=True):
file_path = get_file('vgg16.h5', VGG16_WEIGHTS_PATH, cache_subdir='models')
if verbose:
print('Building VGG16 (no-top) model to generate bottleneck features.')
vgg16_notop = build_vgg_16()
vgg16_notop.load_weights(file_path)
for _ in range(6):
vgg16_notop.pop()
vgg16_notop.compile(optimizer=RMSprop(lr=lr), loss='categorical_crossentropy', metrics=['accuracy'])
if verbose:
print('Bottleneck features generation.')
train_batches = get_batches('train', shuffle=False, class_mode=None, batch_size=BATCH_SIZE)
train_labels = np.array([0]*1000 + [1]*1000)
train_bottleneck = vgg16_notop.predict_generator(train_batches, steps=2000 // BATCH_SIZE)
valid_batches = get_batches('valid', shuffle=False, class_mode=None, batch_size=BATCH_SIZE)
valid_labels = np.array([0]*400 + [1]*400)
valid_bottleneck = vgg16_notop.predict_generator(valid_batches, steps=800 // BATCH_SIZE)
if verbose:
print('Training top model on bottleneck features.')
top_model = Sequential()
top_model.add(Flatten(input_shape=train_bottleneck.shape[1:]))
top_model.add(Dense(4096, activation='relu'))
top_model.add(Dropout(0.5))
top_model.add(Dense(4096, activation='relu'))
top_model.add(Dropout(0.5))
top_model.add(Dense(2, activation='softmax'))
top_model.compile(optimizer=RMSprop(lr=lr), loss='categorical_crossentropy', metrics=['accuracy'])
top_model.fit(train_bottleneck, to_categorical(train_labels),
batch_size=32, epochs=10,
validation_data=(valid_bottleneck, to_categorical(valid_labels)))
if verbose:
print('Concatenate new VGG16 (without top layer) with pretrained top model.')
vgg16_fine = build_vgg_16()
vgg16_fine.load_weights(file_path)
for _ in range(6):
vgg16_fine.pop()
vgg16_fine.add(Flatten(name='top_flatten'))
vgg16_fine.add(Dense(4096, activation='relu'))
vgg16_fine.add(Dropout(0.5))
vgg16_fine.add(Dense(4096, activation='relu'))
vgg16_fine.add(Dropout(0.5))
vgg16_fine.add(Dense(2, activation='softmax'))
vgg16_fine.compile(optimizer=RMSprop(lr=lr), loss='categorical_crossentropy', metrics=['accuracy'])
if verbose:
print('Loading pre-trained weights into concatenated model')
for i, layer in enumerate(reversed(top_model.layers), 1):
pretrained_weights = layer.get_weights()
vgg16_fine.layers[-i].set_weights(pretrained_weights)
for layer in vgg16_fine.layers[:26]:
layer.trainable = False
if verbose:
print('Layers training status:')
for layer in vgg16_fine.layers:
print('[%6s] %s' % ('' if layer.trainable else 'FROZEN', layer.name))
vgg16_fine.compile(optimizer=RMSprop(lr=1e-6), loss='binary_crossentropy', metrics=['accuracy'])
if verbose:
print('Train concatenated model on dogs/cats dataset sample.')
train_datagen = ImageDataGenerator(rescale=1./255,
shear_range=0.2,
zoom_range=0.2,
horizontal_flip=True)
test_datagen = ImageDataGenerator(rescale=1./255)
train_batches = get_batches('train', gen=train_datagen, class_mode='categorical', batch_size=BATCH_SIZE)
valid_batches = get_batches('valid', gen=test_datagen, class_mode='categorical', batch_size=BATCH_SIZE)
vgg16_fine.fit_generator(train_batches, epochs=100,
steps_per_epoch=2000 // BATCH_SIZE,
validation_data=valid_batches,
validation_steps=800 // BATCH_SIZE)
return vgg16_fine
I guess there is a way to achieve much better results with fine-tuning (up to 98%), but I wasn't able to achieve it with provided code. 我想有一种方法可以通过微调(高达98%)获得更好的结果,但我无法用提供的代码实现它。
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