PyTorch手写数字数据集进行多分类

目录

• 一、实现过程
• 0、导包
• 1、准备数据
• 2、设计模型
• 3、构造损失函数和优化器
• 4、训练和测试
• 二、参考文献

一、实现过程

本文对经典手写数字数据集进行多分类，损失函数采用交叉熵，激活函数采用ReLU，优化器采用带有动量的mini-batchSGD算法。

所有代码如下：

0、导包

import torch
from torchvision import transforms,datasets
from torch.utils.data import DataLoader
import torch.nn.functional as F
import torch.optim as optim

1、准备数据

batch_size = 64
transform = transforms.Compose([
  transforms.ToTensor(),
  transforms.Normalize((0.1307,),(0.3081,))
])

# 训练集编程客栈
train_dataset = datasets.MNIST(root='G:/datasets/mnist',train=True,download=False,transform=transform)
train_loader = DataLoader(train_dataset,shuffle=True,batch_size=batch_size)
# 测试集
test_dataset = datasets.MNIST(root='G:/datasets/mnist',train=False,download=False,transform=transform)
test_loader = DataLoader(test_dathttp://www.cppcns.comaset,shuffle=False,batch_size=batch_size)

2、设计模型

class Net(torch.nn.Module):
  def __init__(self):
    super(Net, self).__init__()
    self.l1 = torch.nn.Linear(784, 512)
    www.cppcns.comself.l2 = torch.nn.Linear(512, 256)
    self.l3 = torch.nn.Linear(256, 128)
    self.l4 = torch.nn.Linear(128, 64)
    self.l5 = torch.nn.Linear(64, 10)

  def forward(self, x):
    x = x.view(-1, 784)
    x = F.relu(self.l1(x))
    x = F.relu(self.l2(x))
    x = F.relu(self.l3(x))
    x = F.relu(self.l4(x))
    return self.l5(x)
model = Net()
# 模型加载到GPU上
device = torch.device("cuda:0" if torch.cuda.is_available() else "cpu")
model.to(device)

3、构造损失函数和优化器

criterion = torch.nn.CrossEntropyLoss()
optimizer = optim.SGD(model.parameters(),lr=0.01,momentum=0.5)

4、训练和测试

def train(epoch):
  running_loss = 0.0
  for batch_idx, data in enumerate(train_loader, 0):
    inputs, target = data
    optimizer.zero_grad()

    # forward+backward+update
    outputs = model(inputs.to(device))
    loss = criterion(outputs, target.to(device))
    loss.backward()
    optimizer.step()

    running_loss += loss.item()
    if batch_idx % 300 == 299:
      print('[%d,%d] loss: %.3f' % (e编程客栈poch + 1, batch_idx + 1, running_loss / 300))
      running_loss = 0.0
def test():
  correct = 0
  total = 0
  with torch.no_grad():
    for data in test_loader:
      images, labels = data
      outputs = model(images.to(device))
      _, predicted = torch.max(outputs.data, dim=1)
      total += labels.size(0)
      correct += (predicted.cpu() == labels).sum().item()
  print('Accuracy on test set: %d %%' % (100 * correct / total))

for epoch in range(10):
  train(epoch)
  test()

运行结果如下：

[1,300] loss: 2.166

[1,600] loss: 0.797

[1,900] loss: 0.405

Accuracy on test set: 90 %

[2,300] loss: 0.303

[2,600] loss: 0.252

[2,900] loss: 0.218

Accuracy on test set: 94 %

[3,300] loss: 0.178

[3,600] loss: 0.168

[3,900] loss: 0.142

Accuracy on test set: 95 %

[4,300] loss: 0.129

[4,600] loss: 0.119

[4,900] loss: 0.110

Accuracy on test set: 96 %

[5,300] loss: 0.094

[5,600] loss: 0.092

[5,900] loss: 0.091

Accuracy on test set: 96 %

[6,300] loss: 0.077

[6,600] loss: 0.070

[6,900] loss: 0.075

Accuracy on test set: 97 %

[7,300] loss: 0.061

[7,600] loss: 0.058

[7,900] loss: 0.058

Accuracy on test set: 97 %

[8,300] loss: 0.043

[8,600] loss: 0.051

[8,900] loss: 0.050

Accuracy on test set: 97 %

[9,300] loss: 0.041

[9,600] loss: 0.038

[9,9编程客栈00] loss: 0.043

Accuracy on test set: 97 %

[10,300] loss: 0.030

[10,600] loss: 0.032

[10,900] loss: 0.033

Accuracy on test set: 97 %

二、参考文献

• [1] https://www.bilibili.com/video/BV1Y7411d7Ys?p=9

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