以Hnd数据集做迁移训练
数据准备
Hnd数据集下载：http://www.ee.surrey.ac.uk/CVSSP/demos/chars74k/EnglishHnd.tgz
修改model_fn，可以加载权重数据
先将no_top部分拆开，作为特征提取部分的卷积层，在用数量很少的训练集训练时参数就不允许被修改了
import numpy as np
import tensorflow as tf
import os
from models import BASE_DIR
from models.utils import dataset_input_fn
def cnn_model_no_top(features, trainable):
"""
:param features: 原始输入
:param mode: estimator模式
:param trainable: 该层的变量是否可训练
:return: 不含最上层全连接层的模型
"""
input_layer = tf.reshape(features, [-1, 28, 28, 1])
conv1 = tf.layers.conv2d(inputs=input_layer, filters=32, kernel_size=[5, 5], padding="same", activation=tf.nn.relu, trainable=trainable)
pool1 = tf.layers.max_pooling2d(inputs=conv1, pool_size=[2, 2], strides=2)
conv2 = tf.layers.conv2d(inputs=pool1, filters=64, kernel_size=[5, 5], padding="same", activation=tf.nn.relu, trainable=trainable)
pool2 = tf.layers.max_pooling2d(inputs=conv2, pool_size=[2, 2], strides=2)
pool2_flat = tf.reshape(pool2, shape=[-1, 7 * 7 * 64])
return pool2_flat
def cnn_model_fn(features, labels, mode, params):
"""
用于构造estimator的model_fn
:param features: 输入
:param labels: 标签
:param mode: 模式
:param params: 用于迁移学习和微调训练的参数
nb_classes
transfer
finetune
checkpoints
learning_rate
:return: EstimatorSpec
"""
logits_name = "predictions"
# 把labels转换成ont-hot 形式
labels = tf.one_hot(indices=tf.cast(labels, tf.int32), depth=params["nb_classes"])
# 迁移学习不允许修改底层的参数
model_no_top = cnn_model_no_top(features["x"], trainable=not (params.get("transfer") or params.get("finetune")))
with tf.name_scope("finetune"):
# 此层在第二次迁移学习时允许修改参数，将第二次迁移学习称作微调了
dense = tf.layers.dense(inputs=model_no_top, units=1024, activation=tf.nn.relu, trainable=params.get("finetune"))
dropout = tf.layers.dropout(inputs=dense, rate=0.4, training=(mode == tf.estimator.ModeKeys.TRAIN))
# 最上层任何训练都可以修改参数
logits = tf.layers.dense(inputs=dropout, units=params.get("nb_classes"), name=logits_name)
predictions = {
"classes": tf.argmax(input=logits, axis=1),
"probabilities": tf.nn.softmax(logits, name="softmax_tensor")
}
if mode == tf.estimator.ModeKeys.PREDICT:
return tf.estimator.EstimatorSpec(mode=mode, predictions=predictions)
# 使用softmax交叉熵作为损失函数
loss = tf.losses.softmax_cross_entropy(onehot_labels=labels, logits=logits)
if mode == tf.estimator.ModeKeys.TRAIN:
# 加载已有的存档点参数的方法
if params.get("checkpoints") and isinstance(params.get("checkpoints"), (tuple, list)):
for ckpt in params.get("checkpoints"):
# [0]是存档点路径，[1]为是否加载倒数第二个全连接层参数
if ckpt[1]:
print("restoring base ckpt")
variables_to_restore = tf.contrib.slim.get_variables_to_restore(exclude=[logits_name])
tf.train.init_from_checkpoint(ckpt[0], {v.name.split(':')[0]: v for v in variables_to_restore})
print("restored base ckpt")
else:
print("restoring transferred ckpt")
variables_to_restore = tf.contrib.slim.get_variables_to_restore(exclude=[logits_name,
"finetune", ])
tf.train.init_from_checkpoint(ckpt[0], {v.name.split(':')[0]: v for v in variables_to_restore})
print("restored transferred ckpt")
global_step = tf.train.get_or_create_global_step()
optimizer = tf.train.AdamOptimizer(learning_rate=params.get("learning_rate", 0.0001))
train_op = optimizer.minimize(loss, global_step)
return tf.estimator.EstimatorSpec(mode=mode, loss=loss, train_op=train_op)
eval_metric_ops = {
'accuracy': tf.metrics.accuracy(labels=tf.argmax(labels, 1),
predictions=predictions['classes'],
name='accuracy')
}
return tf.estimator.EstimatorSpec(
mode=mode,
loss=loss,
eval_metric_ops=eval_metric_ops
)
开始训练
首先准备训练数据和验证数据
if __name__ == '__main__':
# 训练MNIST的estimator
mnist_classifier = tf.estimator.Estimator(model_fn=cnn_model_fn, model_dir="./mnist_model", params={
"nb_classes": 10,
})
mnist = tf.contrib.learn.datasets.load_dataset("mnist")
train_data = mnist.train.images
train_labels = np.asarray(mnist.train.labels, dtype=np.int32)
eval_data = mnist.test.images
eval_labels = np.asarray(mnist.test.labels, dtype=np.int32)
# 训练
train_input_fn = tf.estimator.inputs.numpy_input_fn(
x={"x": train_data},
y=np.asarray(train_labels),
batch_size=50, num_epochs=50, shuffle=True
)
mnist_classifier.train(train_input_fn)
# 验证
eval_input_fn = tf.estimator.inputs.numpy_input_fn(
x={"x": eval_data},
y=np.asarray(eval_labels),
batch_size=50, num_epochs=2, shuffle=True
)
eval_result = mnist_classifier.evaluate(eval_input_fn)
print(eval_result) # MNIST数据集上的准确率
# 第一次迁移学习，即只重新训练最上层的全连接层
mnist_classifier = tf.estimator.Estimator(model_fn=cnn_model_fn, model_dir="./mnist_transfer_model", params={
"transfer": True,
"nb_classes": 2,
"checkpoints": [
(os.path.join(BASE_DIR, "models", "mnist", "mnist_model"), True), # (dir, load_dense_layer)
]
})
train_input_fn = dataset_input_fn(
folders=[
os.path.join("D:\\训练集\\Hnd\\Img", "Sample041"), # e
os.path.join("D:\\训练集\\Hnd\\Img", "Sample045"), # i
],
labels=[0, 1],
height=28, width=28, channels=1,
scope_name="train",
epoch=100, batch_size=50,
feature_name="x"
)
mnist_classifier.train(train_input_fn)
eval_input_fn = dataset_input_fn(
folders=[
os.path.join("D:\\验证集\\Hnd\\Img", "Sample041"), # e
os.path.join("D:\\验证集\\Hnd\\Img", "Sample045"), # i
],
labels=[0, 1],
height=28, width=28, channels=1,
scope_name="eval",
epoch=1, batch_size=50,
feature_name="x"
)
result = mnist_classifier.evaluate(eval_input_fn)
print(result)
# 第二次迁移学习，训练所有全连接层
mnist_classifier = tf.estimator.Estimator(model_fn=cnn_model_fn, model_dir="./mnist_finetune_model", params={
"finetune": True,
"nb_classes": 2,
"checkpoints": [(os.path.join(BASE_DIR, "models", "mnist", "mnist_model"), True), # (dir, load_dense_layer)
(os.path.join(BASE_DIR, "models", "mnist", "mnist_transfer_model"), False)
]
})
train_input_fn = dataset_input_fn(
folders=[
os.path.join("D:\\训练集\\Hnd\\Img", "Sample041"), # e
os.path.join("D:\\训练集\\Hnd\\Img", "Sample045"), # i
],
labels=[0, 1],
height=28, width=28, channels=1,
scope_name="train",
epoch=100, batch_size=50,
feature_name="x"
)
mnist_classifier.train(train_input_fn)
eval_input_fn = dataset_input_fn(
folders=[
os.path.join("D:\\验证集\\Hnd\\Img", "Sample041"), # e
os.path.join("D:\\验证集\\Hnd\\Img", "Sample045"), # i
],
labels=[0, 1],
height=28, width=28, channels=1,
scope_name="eval",
epoch=1, batch_size=50,
feature_name="x"
)
result = mnist_classifier.evaluate(eval_input_fn)
print(result)
需要的dataset_input_fn 如下：
import os
from functools import partial
import tensorflow as tf
from tensorflow.python.ops.image_ops_impl import ResizeMethod
# 函数的功能时将filename对应的图片文件读进来，并缩放到统一的大小，再normalize
def load_image_tf(filename, label, height, width, channels=3):
image_string = tf.read_file(filename)
image_decoded = tf.image.decode_image(image_string, channels)
image_decoded.set_shape([None, None, None])
image_decoded = tf.image.central_crop(image_decoded, 1)
image_decoded = tf.image.resize_images(image_decoded, tf.constant([height, width], tf.int32),
method=ResizeMethod.NEAREST_NEIGHBOR)
image_resized = tf.image.resize_image_with_crop_or_pad(image_decoded, height, width)
image_resized = tf.reshape(image_resized, [height, width, channels])
image_resized = tf.divide(image_resized, 255)
image_resized = tf.subtract(image_resized, 0.5)
image_resized = tf.multiply(image_resized, 2.)
return image_resized, label
def read_folder(folders, labels):
if not isinstance(folders, (list, tuple, set)):
raise ValueError("folders 应为list 或 tuple")
all_files = []
all_labels = []
for i, f in enumerate(folders):
files = os.listdir(f)
for file in files:
all_files.append(os.path.join(f, file))
all_labels.append(labels[i])
dataset = tf.data.Dataset.from_tensor_slices((all_files, all_labels))
return dataset, len(all_files)
def dataset_input_fn(folders, labels, epoch, batch_size,
height, width, channels,
scope_name="dataset_input",
feature_name=None):
def fn():
with tf.name_scope(scope_name):
dataset, l = read_folder(folders, labels)
dataset = dataset.map(partial(load_image_tf, height=height, width=width, channels=channels))
dataset = dataset.shuffle(buffer_size=l).repeat(epoch).batch(batch_size)
iterator = dataset.make_one_shot_iterator()
one_element = iterator.get_next()
if feature_name:
return {str(feature_name): one_element[0]}, one_element[1]
return one_element[0], one_element[1]
return fn