CNN-Renew

Pytorch/Project/ez0/HandWriteMLP.py

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+import torch
+import matplotlib.pyplot as plt
+from torch import nn
+import torch.optim as optim
+from torchvision import datasets, transforms
+from torch.utils.data import DataLoader
+
+from main import optimizer
+
+# 设置超参数
+batch_size = 64
+
+# 定义预处理步骤
+transform = transforms.Compose([
+    transforms.ToTensor(),  # 转换为张量，范围 [0,1]
+    transforms.Normalize((0.1307,), (0.3081,))  # 标准化：均值、方差是 MNIST 的经验值
+])
+
+# 加载训练集
+train_dataset = datasets.MNIST(
+    root='./data',       # 数据存放路径
+    train=True,          # 训练集
+    download=True,       # 如果没有就下载
+    transform=transform  # 应用预处理
+)
+
+# 加载测试集
+test_dataset = datasets.MNIST(
+    root='./data',
+    train=False,         # 测试集
+    download=True,
+    transform=transform
+)
+
+# 构建 DataLoader
+train_loader = DataLoader(
+    dataset=train_dataset,
+    batch_size=batch_size,
+    shuffle=True         # 打乱数据，适合训练
+)
+
+test_loader = DataLoader(
+    dataset=test_dataset,
+    batch_size=batch_size,
+    shuffle=False        # 测试集不需要打乱
+)
+
+# 简单测试一下
+print(f"训练集大小: {len(train_dataset)}")
+print(f"测试集大小: {len(test_dataset)}")
+
+# 取一个 batch 看看形状
+images, labels = next(iter(train_loader))
+print(f"图片批次维度: {images.shape}")   # [batch_size, 1, 28, 28]
+print(f"标签批次维度: {labels.shape}")   # [batch_size]
+
+# 从训练集中取一个 batch
+images, labels = next(iter(train_loader))
+'''
+# 画前 9 张图
+fig, axes = plt.subplots(3, 3, figsize=(6, 6))
+for i, ax in enumerate(axes.flat):
+    img = images[i].squeeze().numpy()  # [1,28,28] -> [28,28]
+    label = labels[i].item()
+    ax.imshow(img, cmap="gray")
+    ax.set_title(f"Label: {label}")
+    ax.axis("off")
+
+plt.tight_layout()
+plt.show()
+'''
+
+ez = nn.Sequential(
+    nn.Linear(28 * 28, 256),
+    nn.ReLU(),
+    nn.Linear(256, 100),
+    nn.ReLU(),
+    nn.Linear(100, 10),
+)
+criterion = nn.CrossEntropyLoss()
+
+optimizer = optim.Adam(ez.parameters(), lr=0.002)
+
+for images, labels in train_loader:
+    images = images.view(images.size(0), -1)  # [batch_size, 28*28]
+    out = ez(images)
+    loss = criterion(out, labels)
+    #反向传播
+    optimizer.zero_grad()
+    loss.backward()
+    optimizer.step()
+    print(f"<UNK>: {loss}")
+
+#训练结束
+ez.eval()  # 关闭 dropout/batchnorm 等训练特性
+
+correct = 0
+total = 0
+
+with torch.no_grad():  # 测试不需要计算梯度，节省显存
+    for images, labels in test_loader:
+        images = images.view(images.size(0), -1)  # flatten
+        outputs = ez(images)                       # [batch_size, 10]
+
+        # 取每行最大值对应的索引作为预测类别
+        _, predicted = torch.max(outputs, 1)
+
+        total += labels.size(0)
+        correct += (predicted == labels).sum().item()
+
+print(f"测试集准确率: {correct}/{total} = {correct/total*100:.2f}%")