参考

3.7. softmax回归的简洁实现

使用pytorch实现softmax

import torch from torch import nn from torch.nn import init import numpy as np import sys sys.path.append("..") import d2lzh_pytorch as d2l

3.7.1. 获取和读取数据

batch_size = 256 train_iter, test_iter = d2l.load_data_fashion_mnist(batch_size)

3.7.2. 定义和初始化模型

num_inputs = 784 num_outputs = 10class LinearNet(nn.Module):def __init__(self, num_inputs, num_outputs):super(LinearNet, self).__init__()self.linear = nn.Linear(num_inputs, num_outputs) def forward(self, x):y = self.linear(x.view(x.shape[0], -1))return y net = LinearNet(num_inputs, num_outputs)init.normal_(net.linear.weight, mean=0, std=0.01) init.constant_(net.linear.bias, val=0)

3.7.3. softmax和交叉熵损失函数

loss = nn.CrossEntropyLoss()

3.7.4. 定义优化算法

optimizer = torch.optim.SGD(net.parameters(), lr=0.1)

3.7.5. 训练模型

num_epochs = 5 d2l.train_ch3(net, train_iter, test_iter, loss, num_epochs, batch_size, None, None, optimizer)

3.7.6. 测试

# 测试 X, y = iter(test_iter).next()true_labels = d2l.get_fashion_mnist_labels(y.numpy()) pred_labels = d2l.get_fashion_mnist_labels(net(X).argmax(dim=1).numpy()) titles = [true + '\n' + pred for true, pred in zip(true_labels, pred_labels)]d2l.show_fashion_mnist(X[0:9], titles[0:9])

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