在使用Adam优化时,需要注意参数的初始化和学习率的设置。对于逻辑回归模型,我们可以采用以下方式对Adam优化进行适配:
import tensorflow as tf
# 定义逻辑回归模型
class LogisticRegression(tf.keras.Model):
def __init__(self, input_size, num_classes):
super(LogisticRegression, self).__init__()
self.linear = tf.keras.layers.Dense(num_classes, input_shape=(input_size,), activation='softmax')
def call(self, x):
return self.linear(x)
# 定义优化器
optimizer = tf.keras.optimizers.Adam(learning_rate=0.01)
# 定义模型
model = LogisticRegression(input_size=2, num_classes=2)
# 定义损失函数
loss_object = tf.keras.losses.SparseCategoricalCrossentropy(from_logits=True)
# 定义评价指标
train_loss = tf.keras.metrics.Mean(name='train_loss')
train_accuracy = tf.keras.metrics.SparseCategoricalAccuracy(name='train_accuracy')
# 定义训练步骤
@tf.function
def train_step(x, y):
with tf.GradientTape() as tape:
# 预测结果
predictions = model(x)
# 计算损失函数值
loss = loss_object(y, predictions)
# 计算梯度
gradients = tape.gradient(loss, model.trainable_variables)
# 应用梯度更新模型参数
optimizer.apply_gradients(zip(gradients, model.trainable_variables))
# 记录损失函数值和评价指标的值
train_loss(loss)
train_accuracy(y, predictions)
# 定义数据集
train_ds = tf.data.Dataset.from_tensor_slices((x_train, y_train)).batch(32)
# 训练模型
for epoch in range(num_epochs):
# 重置评价指标的状态
train_loss.reset_states()
train_accuracy.reset_states()
# 遍历数据集并训练模型
for x, y in train_ds:
train_step(x, y)
# 输出训练结果
print('Epoch {}/{}, Loss: {}, Accuracy: {}'.format(
epoch+1,
num_epochs,
train_loss.result(),
train_accuracy.result()
))
在这段代码中,我们定义了一个名为LogisticRegression的类,它继承自tf.keras.Model