一小时学会TensorFlow2之Fashion Mnist

描述

Fashion Mnist 是一个类似于 Mnist 的图像数据集. 涵盖 10 种类别的 7 万 (6 万训练集 + 1 万测试集) 个不同商品的图片.

Tensorboard

Tensorboard 是 tensorflow 的一个可视化工具.

创建 summary

我们可以通过tf.summary.create_file_writer(file_path)来创建一个新的 summary 实例.

例子:

# 将当前时间作为子文件名
current_time = datetime.datetime.now().strftime("％Y％m％d-％H％M％S")

# 监听的文件的路径
log_dir = 'logs/' + current_time

# 创建writer
summary_writer = tf.summary.create_file_writer(log_dir)

存入数据

通过tf.summary.scalar我们可以向 summary 对象存入数据.

格式:

tf.summary.scalar(
   name, data, step=None, description=None
)

例子:

with summary_writer.as_default():
   tf.summary.scalar("train-loss", float(Cross_Entropy), step=step)

metrics

metrics.Mean()

metrics.Mean()可以帮助我们计算平均数.

格式:

tf.keras.metrics.Mean(
   name='mean', dtype=None
)

例子:

# 准确率表
loss_meter = tf.keras.metrics.Mean()

metrics.Accuracy()

格式:

tf.keras.metrics.Accuracy(
   name='accuracy', dtype=None
)

例子:

# 损失表
acc_meter = tf.keras.metrics.Accuracy()

变量更新 &重置

我们可以通过update_state来实现变量更新, 通过rest_state来实现变量重置.

例如:

# 跟新损失
loss_meter.update_state(Cross_Entropy)

# 重置
loss_meter.reset_state()

案例

pre_process 函数

def pre_process(x, y):
   """
   数据预处理
   :param x: 特征值
   :param y: 目标值
   :return: 返回处理好的x, y
   """
   # 转换x
   x = tf.cast(x, tf.float32) / 255
   x = tf.reshape(x, [-1, 784])

# 转换y
   y = tf.cast(y, dtype=tf.int32)
   y = tf.one_hot(y, depth=10)

return x, y

get_data 函数

def get_data():
   """
   获取数据
   :return: 返回分批完的训练集和测试集
   """

# 获取数据
   (X_train, y_train), (X_test, y_test) = tf.keras.datasets.fashion_mnist.load_data()

# 分割训练集
   train_db = tf.data.Dataset.from_tensor_slices((X_train, y_train)).shuffle(60000, seed=0)
   train_db = train_db.batch(batch_size).map(pre_process)

# 分割测试集
   test_db = tf.data.Dataset.from_tensor_slices((X_test, y_test)).shuffle(10000, seed=0)
   test_db = test_db.batch(batch_size).map(pre_process)

# 返回
   return train_db, test_db

train 函数

def train(epoch, train_db):
   """
   训练数据
   :param train_db: 分批的数据集
   :return: 无返回值
   """
   for step, (x, y) in enumerate(train_db):
       with tf.GradientTape() as tape:

# 获取模型输出结果
           logits = model(x)

# 计算交叉熵
           Cross_Entropy = tf.losses.categorical_crossentropy(y, logits, from_logits=True)
           Cross_Entropy = tf.reduce_sum(Cross_Entropy)

# 跟新损失
           loss_meter.update_state(Cross_Entropy)

# 计算梯度
       grads = tape.gradient(Cross_Entropy, model.trainable_variables)

# 跟新参数
       optimizer.apply_gradients(zip(grads, model.trainable_variables))

# 每100批调试输出一下误差
       if step ％ 100 == 0:
           print("step:", step, "Cross_Entropy:", loss_meter.result().numpy())

# 重置
           loss_meter.reset_state()

# 可视化
           with summary_writer.as_default():
               tf.summary.scalar("train-loss", float(Cross_Entropy), step= epoch * 235 + step)

test 函数

def test(epoch, test_db):
   """
   测试模型
   :param epoch: 轮数
   :param test_db: 分批的测试集
   :return: 无返回值
   """

# 重置
   acc_meter.reset_state()

for x, y in test_db:
       # 获取模型输出结果
       logits = model(x)

# 预测结果
       pred = tf.argmax(logits, axis=1)

# 从one_hot编码变回来
       y = tf.argmax(y, axis=1)

# 计算准确率
       acc_meter.update_state(y, pred)

# 调试输出
   print("epoch:", epoch + 1, "Accuracy:", acc_meter.result().numpy() * 100, "％", )

# 可视化
   with summary_writer.as_default():
       tf.summary.scalar("val-acc", acc_meter.result().numpy(), step=epoch * 235)

main 函数

def main():
   """
   主函数
   :return: 无返回值
   """

# 获取数据
   train_db, test_db = get_data()

# 轮期
   for epoch in range(iteration_num):
       train(epoch, train_db)
       test(epoch, test_db)

完整代码

import datetime
import tensorflow as tf

# 定义超参数
batch_size = 256  # 一次训练的样本数目
learning_rate = 0.001  # 学习率
iteration_num = 20  # 迭代次数

# 优化器
optimizer = tf.keras.optimizers.Adam(learning_rate=learning_rate)

# 准确率表
loss_meter = tf.keras.metrics.Mean()

# 损失表
acc_meter = tf.keras.metrics.Accuracy()

# 可视化
current_time = datetime.datetime.now().strftime("％Y％m％d-％H％M％S")
log_dir = 'logs/' + current_time
summary_writer = tf.summary.create_file_writer(log_dir)  # 创建writer

# 模型
model = tf.keras.Sequential([
   tf.keras.layers.Dense(256, activation=tf.nn.relu),
   tf.keras.layers.Dense(128, activation=tf.nn.relu),
   tf.keras.layers.Dense(64, activation=tf.nn.relu),
   tf.keras.layers.Dense(32, activation=tf.nn.relu),
   tf.keras.layers.Dense(10)
])

# 调试输出summary
model.build(input_shape=[None, 28 * 28])
print(model.summary())

def pre_process(x, y):
   """
   数据预处理
   :param x: 特征值
   :param y: 目标值
   :return: 返回处理好的x, y
   """
   # 转换x
   x = tf.cast(x, tf.float32) / 255
   x = tf.reshape(x, [-1, 784])

# 转换y
   y = tf.cast(y, dtype=tf.int32)
   y = tf.one_hot(y, depth=10)

return x, y

def get_data():
   """
   获取数据
   :return: 返回分批完的训练集和测试集
   """

# 获取数据
   (X_train, y_train), (X_test, y_test) = tf.keras.datasets.fashion_mnist.load_data()

# 分割训练集
   train_db = tf.data.Dataset.from_tensor_slices((X_train, y_train)).shuffle(60000, seed=0)
   train_db = train_db.batch(batch_size).map(pre_process)

# 分割测试集
   test_db = tf.data.Dataset.from_tensor_slices((X_test, y_test)).shuffle(10000, seed=0)
   test_db = test_db.batch(batch_size).map(pre_process)

# 返回
   return train_db, test_db

def train(epoch, train_db):
   """
   训练数据
   :param train_db: 分批的数据集
   :return: 无返回值
   """
   for step, (x, y) in enumerate(train_db):
       with tf.GradientTape() as tape:

# 获取模型输出结果
           logits = model(x)

# 计算交叉熵
           Cross_Entropy = tf.losses.categorical_crossentropy(y, logits, from_logits=True)
           Cross_Entropy = tf.reduce_sum(Cross_Entropy)

# 跟新损失
           loss_meter.update_state(Cross_Entropy)

# 计算梯度
       grads = tape.gradient(Cross_Entropy, model.trainable_variables)

# 跟新参数
       optimizer.apply_gradients(zip(grads, model.trainable_variables))

# 每100批调试输出一下误差
       if step ％ 100 == 0:
           print("step:", step, "Cross_Entropy:", loss_meter.result().numpy())

# 重置
           loss_meter.reset_state()

# 可视化
           with summary_writer.as_default():
               tf.summary.scalar("train-loss", float(Cross_Entropy), step=epoch * 235 + step)

def test(epoch, test_db):
   """
   测试模型
   :param epoch: 轮数
   :param test_db: 分批的测试集
   :return: 无返回值
   """

# 重置
   acc_meter.reset_state()

for x, y in test_db:
       # 获取模型输出结果
       logits = model(x)

# 预测结果
       pred = tf.argmax(logits, axis=1)

# 从one_hot编码变回来
       y = tf.argmax(y, axis=1)

# 计算准确率
       acc_meter.update_state(y, pred)

# 调试输出
   print("epoch:", epoch + 1, "Accuracy:", acc_meter.result().numpy() * 100, "％", )

# 可视化
   with summary_writer.as_default():
       tf.summary.scalar("val-acc", acc_meter.result().numpy(), step=epoch * 235)

def main():
   """
   主函数
   :return: 无返回值
   """

# 获取数据
   train_db, test_db = get_data()

# 轮期
   for epoch in range(iteration_num):
       train(epoch, train_db)
       test(epoch, test_db)

if __name__ == "__main__":
   main()

输出结果:

Model: "sequential"
_________________________________________________________________
Layer (type) Output Shape Param #
=================================================================
dense (Dense) (None, 256) 200960
_________________________________________________________________
dense_1 (Dense) (None, 128) 32896
_________________________________________________________________
dense_2 (Dense) (None, 64) 8256
_________________________________________________________________
dense_3 (Dense) (None, 32) 2080
_________________________________________________________________
dense_4 (Dense) (None, 10) 330
=================================================================
Total params: 244,522
Trainable params: 244,522
Non-trainable params: 0
_________________________________________________________________
None
2021-06-14 18:01:27.399812: I tensorflow/compiler/mlir/mlir_graph_optimization_pass.cc:176] None of the MLIR Optimization Passes are enabled (registered 2)
step: 0 Cross_Entropy: 591.5974
step: 100 Cross_Entropy: 196.49309
step: 200 Cross_Entropy: 125.2562
epoch: 1 Accuracy: 84.72999930381775 ％
step: 0 Cross_Entropy: 107.64579
step: 100 Cross_Entropy: 105.854385
step: 200 Cross_Entropy: 99.545975
epoch: 2 Accuracy: 85.83999872207642 ％
step: 0 Cross_Entropy: 95.42945
step: 100 Cross_Entropy: 91.366234
step: 200 Cross_Entropy: 90.84072
epoch: 3 Accuracy: 86.69999837875366 ％
step: 0 Cross_Entropy: 82.03317
step: 100 Cross_Entropy: 83.20552
step: 200 Cross_Entropy: 81.57012
epoch: 4 Accuracy: 86.11000180244446 ％
step: 0 Cross_Entropy: 82.94046
step: 100 Cross_Entropy: 77.56677
step: 200 Cross_Entropy: 76.996346
epoch: 5 Accuracy: 87.27999925613403 ％
step: 0 Cross_Entropy: 75.59219
step: 100 Cross_Entropy: 71.70899
step: 200 Cross_Entropy: 74.15144
epoch: 6 Accuracy: 87.29000091552734 ％
step: 0 Cross_Entropy: 76.65844
step: 100 Cross_Entropy: 70.09151
step: 200 Cross_Entropy: 70.84446
epoch: 7 Accuracy: 88.27999830245972 ％
step: 0 Cross_Entropy: 67.50707
step: 100 Cross_Entropy: 64.85907
step: 200 Cross_Entropy: 68.63099
epoch: 8 Accuracy: 88.41999769210815 ％
step: 0 Cross_Entropy: 65.50318
step: 100 Cross_Entropy: 62.2706
step: 200 Cross_Entropy: 63.80803
epoch: 9 Accuracy: 86.21000051498413 ％
step: 0 Cross_Entropy: 66.95486
step: 100 Cross_Entropy: 61.84385
step: 200 Cross_Entropy: 62.18851
epoch: 10 Accuracy: 88.45999836921692 ％
step: 0 Cross_Entropy: 59.779297
step: 100 Cross_Entropy: 58.602314
step: 200 Cross_Entropy: 59.837025
epoch: 11 Accuracy: 88.66000175476074 ％
step: 0 Cross_Entropy: 58.10068
step: 100 Cross_Entropy: 55.097878
step: 200 Cross_Entropy: 59.906315
epoch: 12 Accuracy: 88.70999813079834 ％
step: 0 Cross_Entropy: 57.584858
step: 100 Cross_Entropy: 54.95376
step: 200 Cross_Entropy: 55.797752
epoch: 13 Accuracy: 88.44000101089478 ％
step: 0 Cross_Entropy: 53.54782
step: 100 Cross_Entropy: 53.62939
step: 200 Cross_Entropy: 54.632828
epoch: 14 Accuracy: 87.02999949455261 ％
step: 0 Cross_Entropy: 54.387398
step: 100 Cross_Entropy: 52.323734
step: 200 Cross_Entropy: 53.968185
epoch: 15 Accuracy: 88.98000121116638 ％
step: 0 Cross_Entropy: 50.468914
step: 100 Cross_Entropy: 50.79311
step: 200 Cross_Entropy: 51.296227
epoch: 16 Accuracy: 88.67999911308289 ％
step: 0 Cross_Entropy: 48.753258
step: 100 Cross_Entropy: 46.809692
step: 200 Cross_Entropy: 48.08208
epoch: 17 Accuracy: 89.10999894142151 ％
step: 0 Cross_Entropy: 46.830627
step: 100 Cross_Entropy: 47.208813
step: 200 Cross_Entropy: 48.671318
epoch: 18 Accuracy: 88.77999782562256 ％
step: 0 Cross_Entropy: 46.15514
step: 100 Cross_Entropy: 45.026627
step: 200 Cross_Entropy: 45.371685
epoch: 19 Accuracy: 88.7399971485138 ％
step: 0 Cross_Entropy: 47.696465
step: 100 Cross_Entropy: 41.52749
step: 200 Cross_Entropy: 46.71362
epoch: 20 Accuracy: 89.56000208854675 ％

可视化

来源：https://iamarookie.blog.csdn.net/article/details/117917350