基于pytorch的LeNet模型构建

admin • 2021-11-19 20:48 • 人工智能

上文我们利用pytorch构建了BP神经网络，这次我们来构建CNN的经典网络LeNet，还是利用MNIST数据集，具体的数据获取方法本文不详细介绍，只介绍如何搭建模型并训练数据集。LeNet神经网络由深度学习三巨头之一的Yan LeCun提出，他同时也是卷积神经网络 (CNN，Convolutional Neural Networks)之父。LeNet最早是用在手写数字的识别上，效果较好。主要包含了卷积层、池化层、全连接层等，这里不讲解概念，只介绍如何搭建模型。后续可能会针对这些内容进行介绍。

1、网络结构

图片来自于论文中截取。

根据网络架构可以看到，模型当中输入维度为32*32，输出维度为1*10。

LeNet 网络结构
网络层	input	卷积核	卷积核数目	output
输入层	32321	/	/	/
C1层-卷积层	32321	5*5	6	28286
S2层-池化层	28286	2*2	/	14146
C3层-卷积层	14146	5*5	16	101016
S4层-池化层	101016	2*2	/	5516
C5层-全连接层	5516	/	/	1*120
C6层-全连接层	1*120	/	/	1*84
输出层	1*84	/	/	1*10

根据上述结构利用pytorch构建：

import torch
from torch import nn


class LeNet(nn.Module):
    def __init__(self):
        super(LeNet, self).__init__()

        self.c1 = nn.Sequential(
            nn.Conv2d(1, 6, (5,5),stride=1,padding=0),
            nn.ReLU()
        )
        self.s2 = nn.MaxPool2d((2,2), padding=0)
        self.c3 = nn.Sequential(
            nn.Conv2d(6, 16, (5,5),stride=1,padding=0),
            nn.ReLU()
        )
        self.s4 = nn.MaxPool2d((2,2), padding=0)
        self.c5 = nn.Sequential(
            nn.Linear(5*5*16, 120),
            nn.ReLU()
        )
        self.c6 = nn.Sequential(
            nn.Linear(120, 84),
            nn.ReLU()
        )
        self.out = nn.Sequential(
            nn.Linear(84, 10),
            nn.Sigmoid()
        )

    def forward(self, x):
        x = self.c1(x)
        print(x.shape)
        x = self.s2(x)
        print(x.shape)
        x = self.c3(x)
        print(x.shape)
        x = self.s4(x)
        print(x.shape)
        x = x.view(-1,5*5*16)
        x = self.c5(x)
        print(x.shape)
        x = self.c6(x)
        print(x.shape)
        x = self.out(x)
        print(x.shape)
        return x


inp = torch.randn(1, 1,32,32)
le = LeNet()
out = le(inp)

并且打印每一层的shape，结果如下：

torch.Size([1, 6, 28, 28])
torch.Size([1, 6, 14, 14])
torch.Size([1, 16, 10, 10])
torch.Size([1, 16, 5, 5])
torch.Size([1, 120])
torch.Size([1, 84])
torch.Size([1, 10])

2、利用MNIST数据集训练模型

利用数据集训练模型，其余内容与上一节内容相同，这里不在赘述，直接上代码。

import torch
from torchvision import datasets, transforms
import torch.nn as nn
import torch.optim as optim
from torch.autograd import Variable
import numpy as np


device = torch.device('cuda:0')


class Config:
    batch_size = 128
    epoch = 10
    alpha = 1e-3
    print_per_step = 100  # 控制输出


class LeNet(nn.Module):
    def __init__(self):
        super(LeNet, self).__init__()

        self.c1 = nn.Sequential(
            nn.Conv2d(1, 6, (5,5),stride=1,padding=0),
            nn.ReLU()
        )
        self.s2 = nn.MaxPool2d((2,2), padding=0)
        self.c3 = nn.Sequential(
            nn.Conv2d(6, 16, (5,5),stride=1,padding=0),
            nn.ReLU()
        )
        self.s4 = nn.MaxPool2d((2,2), padding=0)
        self.c5 = nn.Sequential(
            nn.Linear(5*5*16, 120),
            nn.ReLU()
        )
        self.c6 = nn.Sequential(
            nn.Linear(120, 84),
            nn.ReLU()
        )
        self.out = nn.Sequential(
            nn.Linear(84, 10),
            nn.Sigmoid()
        )

    def forward(self, x):
        x = self.c1(x)
        x = self.s2(x)
        x = self.c3(x)
        x = self.s4(x)
        x = x.view(-1,5*5*16)
        x = self.c5(x)
        x = self.c6(x)
        x = self.out(x)
        return x


class TrainProcess:
    def __init__(self):
        self.train, self.test = self.load_data()
        self.net = LeNet().to(device)
        self.criterion = nn.CrossEntropyLoss()  # 定义损失函数
        self.optimizer = optim.Adam(self.net.parameters(), lr=Config.alpha)

    @staticmethod
    def load_data():
        train_data = datasets.MNIST(root='./data/',
                                    train=True,
                                    transform=transforms.Compose([
                                            transforms.Resize((32, 32)),transforms.ToTensor()]
                                        ),
                                    download=True)

        test_data = datasets.MNIST(root='./data/',
                                   train=False,
                                   transform=transforms.Compose([
                                       transforms.Resize((32, 32)), transforms.ToTensor()]
                                   ))

        # 返回一个数据迭代器
        # shuffle：是否打乱顺序
        train_loader = torch.utils.data.DataLoader(dataset=train_data,
                                                   batch_size=Config.batch_size,
                                                   shuffle=True)

        test_loader = torch.utils.data.DataLoader(dataset=test_data,
                                                  batch_size=Config.batch_size,
                                                  shuffle=False)
        return train_loader, test_loader

    def train_step(self):
        print("Training & Evaluating based on LeNet......")
        file = './result/train_mnist.txt'
        fp = open(file,'w',encoding='utf-8')
        fp.write('epochtbatchtlosstaccuracyn')
        for epoch in range(Config.epoch):
            print("Epoch {:3}.".format(epoch + 1))
            for batch_idx,(data,label) in enumerate(self.train):
                data, label = Variable(data.cuda()), Variable(label.cuda())
                self.optimizer.zero_grad()
                outputs = self.net(data)
                loss =self.criterion(outputs, label)
                loss.backward()
                self.optimizer.step()
                # 每100次打印一次结果
                if batch_idx % Config.print_per_step == 0:
                    _, predicted = torch.max(outputs, 1)
                    correct = 0
                    for _ in predicted == label:
                        if _:
                            correct += 1
                    accuracy = correct / Config.batch_size
                    msg = "Batch: {:5}, Loss: {:6.2f}, Accuracy: {:8.2%}."
                    print(msg.format(batch_idx, loss, accuracy))
                    fp.write('{}t{}t{}t{}n'.format(epoch,batch_idx,loss,accuracy))
        fp.close()
        test_loss = 0.
        test_correct = 0
        for data, label in self.test:
            data, label = Variable(data.cuda()), Variable(label.cuda())
            outputs = self.net(data)
            loss = self.criterion(outputs, label)
            test_loss += loss * Config.batch_size
            _, predicted = torch.max(outputs, 1)
            correct = 0
            for _ in predicted == label:
                if _:
                    correct += 1
            test_correct += correct
        accuracy = test_correct / len(self.test.dataset)
        loss = test_loss / len(self.test.dataset)
        print("Test Loss: {:5.2f}, Accuracy: {:6.2%}".format(loss, accuracy))
        torch.save(self.net.state_dict(), './result/raw_train_mnist_model.pth')


if __name__ == "__main__":
    p = TrainProcess()
    p.train_step()

需要强调的是，由于MNIST数据集的尺寸为28*28，因此需要在读取数据是进行尺寸转换。

transforms.Compose([
    transforms.Resize((32, 32)), transforms.ToTensor()]
)

这里主要是将数据集修改尺寸，并且将数据类型转换成Tensor。训练部分可以认为是固定的一套模板或流程，在解决一些常规问题上是可以通用的。训练结果如下：

Training & Evaluating based on LeNet......
Epoch   1.
Batch:     0, Loss:   2.30, Accuracy:    8.59%.
Batch:   100, Loss:   1.62, Accuracy:   80.47%.
Batch:   200, Loss:   1.57, Accuracy:   89.06%.
Batch:   300, Loss:   1.56, Accuracy:   90.62%.
Batch:   400, Loss:   1.54, Accuracy:   92.97%.
Epoch   2.
Batch:     0, Loss:   1.52, Accuracy:   92.97%.
Batch:   100, Loss:   1.50, Accuracy:   96.88%.
Batch:   200, Loss:   1.52, Accuracy:   89.06%.
Batch:   300, Loss:   1.50, Accuracy:   92.97%.
Batch:   400, Loss:   1.49, Accuracy:   95.31%.
Epoch   3.
Batch:     0, Loss:   1.50, Accuracy:   94.53%.
Batch:   100, Loss:   1.50, Accuracy:   97.66%.
Batch:   200, Loss:   1.48, Accuracy:   96.88%.
Batch:   300, Loss:   1.50, Accuracy:   95.31%.
Batch:   400, Loss:   1.48, Accuracy:   97.66%.
Epoch   4.
Batch:     0, Loss:   1.47, Accuracy:   96.88%.
Batch:   100, Loss:   1.48, Accuracy:   96.88%.
Batch:   200, Loss:   1.49, Accuracy:   97.66%.
Batch:   300, Loss:   1.48, Accuracy:   98.44%.
Batch:   400, Loss:   1.47, Accuracy:   96.88%.
Epoch   5.
Batch:     0, Loss:   1.47, Accuracy:  100.00%.
Batch:   100, Loss:   1.49, Accuracy:   96.88%.
Batch:   200, Loss:   1.48, Accuracy:   97.66%.
Batch:   300, Loss:   1.48, Accuracy:   96.88%.
Batch:   400, Loss:   1.48, Accuracy:   96.88%.
Epoch   6.
Batch:     0, Loss:   1.47, Accuracy:   98.44%.
Batch:   100, Loss:   1.47, Accuracy:   98.44%.
Batch:   200, Loss:   1.47, Accuracy:   99.22%.
Batch:   300, Loss:   1.47, Accuracy:   99.22%.
Batch:   400, Loss:   1.49, Accuracy:   98.44%.
Epoch   7.
Batch:     0, Loss:   1.48, Accuracy:   97.66%.
Batch:   100, Loss:   1.49, Accuracy:   97.66%.
Batch:   200, Loss:   1.47, Accuracy:   99.22%.
Batch:   300, Loss:   1.48, Accuracy:   98.44%.
Batch:   400, Loss:   1.48, Accuracy:   97.66%.
Epoch   8.
Batch:     0, Loss:   1.48, Accuracy:   98.44%.
Batch:   100, Loss:   1.48, Accuracy:   98.44%.
Batch:   200, Loss:   1.47, Accuracy:  100.00%.
Batch:   300, Loss:   1.48, Accuracy:   98.44%.
Batch:   400, Loss:   1.47, Accuracy:   99.22%.
Epoch   9.
Batch:     0, Loss:   1.46, Accuracy:   99.22%.
Batch:   100, Loss:   1.46, Accuracy:  100.00%.
Batch:   200, Loss:   1.49, Accuracy:   96.09%.
Batch:   300, Loss:   1.47, Accuracy:   97.66%.
Batch:   400, Loss:   1.46, Accuracy:  100.00%.
Epoch  10.
Batch:     0, Loss:   1.47, Accuracy:   98.44%.
Batch:   100, Loss:   1.47, Accuracy:   99.22%.
Batch:   200, Loss:   1.47, Accuracy:   98.44%.
Batch:   300, Loss:   1.47, Accuracy:   99.22%.
Batch:   400, Loss:   1.47, Accuracy:  100.00%.
Test Loss:  1.49, Accuracy: 98.39%

较之前的BP网络有所提升。

本图文内容来源于网友网络收集整理提供，作为学习参考使用，版权属于原作者。

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