深度学习每周学习总结J1（ResNet-50算法实战与解析 - 鸟类识别）

🍨 本文为🔗365天深度学习训练营中的学习记录博客

🍖 原作者：K同学啊 | 接辅导、项目定制

- - [0. 总结](#0. 总结)
  - [1. 设置GPU](#1. 设置GPU)
  - [2. 导入数据及处理部分](#2. 导入数据及处理部分)
  - [3. 划分数据集](#3. 划分数据集)
  - [4. 模型构建部分](#4. 模型构建部分)
  - [5. 设置超参数：定义损失函数，学习率，以及根据学习率定义优化器等](#5. 设置超参数：定义损失函数，学习率，以及根据学习率定义优化器等)
  - [6. 训练函数](#6. 训练函数)
  - [7. 测试函数](#7. 测试函数)
  - [7. 正式训练](#7. 正式训练)
  - [9. 结果可视化](#9. 结果可视化)
  - [10. 模型的保存](#10. 模型的保存)
  - [11. 使用训练好的模型进行预测](#11. 使用训练好的模型进行预测)

0. 总结

数据导入及处理部分：本次数据导入没有使用torchvision自带的数据集，需要将原始数据进行处理包括数据导入，查看数据分类情况，定义transforms，进行数据类型转换等操作。

划分数据集：划定训练集测试集后，再使用torch.utils.data中的DataLoader()分别加载上一步处理好的训练及测试数据，查看批处理维度.

模型构建部分：resnet-50

设置超参数：在这之前需要定义损失函数，学习率（动态学习率），以及根据学习率定义优化器（例如SGD随机梯度下降），用来在训练中更新参数，最小化损失函数。

定义训练函数：函数的传入的参数有四个，分别是设置好的DataLoader(),定义好的模型，损失函数，优化器。函数内部初始化损失准确率为0，接着开始循环，使用DataLoader()获取一个批次的数据，对这个批次的数据带入模型得到预测值，然后使用损失函数计算得到损失值。接下来就是进行反向传播以及使用优化器优化参数，梯度清零放在反向传播之前或者是使用优化器优化之后都是可以的，一般是默认放在反向传播之前。

定义测试函数：函数传入的参数相比训练函数少了优化器，只需传入设置好的DataLoader(),定义好的模型，损失函数。此外除了处理批次数据时无需再设置梯度清零、返向传播以及优化器优化参数，其余部分均和训练函数保持一致。

训练过程：定义训练次数，有几次就使用整个数据集进行几次训练，初始化四个空list分别存储每次训练及测试的准确率及损失。使用model.train()开启训练模式，调用训练函数得到准确率及损失。使用model.eval()将模型设置为评估模式，调用测试函数得到准确率及损失。接着就是将得到的训练及测试的准确率及损失存储到相应list中并合并打印出来，得到每一次整体训练后的准确率及损失。

结果可视化

模型的保存，调取及使用。在PyTorch中，通常使用 torch.save(model.state_dict(), 'model.pth') 保存模型的参数，使用 model.load_state_dict(torch.load('model.pth')) 加载参数。

需要改进优化的地方：在保证整体流程没有问题的情况下，继续细化细节研究，比如一些函数的原理及作用，如何提升训练集准确率等问题。

python 复制代码

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

import os,PIL,pathlib
import matplotlib.pyplot as plt
import warnings

warnings.filterwarnings('ignore') # 忽略警告信息

plt.rcParams['font.sans-serif'] = ['SimHei'] # 用来正常显示中文标签
plt.rcParams['axes.unicode_minus'] = False   # 用来正常显示负号
plt.rcParams['figure.dpi'] = 100 # 分辨率

1. 设置GPU

python 复制代码

device = torch.device("cuda" if torch.cuda.is_available() else "cpu")
device

device(type='cuda')

2. 导入数据及处理部分

python 复制代码

# 获取数据分布情况
path_dir = './data/bird_photos/'
path_dir = pathlib.Path(path_dir)

paths = list(path_dir.glob('*'))
# classNames = [str(path).split("\\")[-1] for path in paths] # ['Bananaquit', 'Black Skimmer', 'Black Throated Bushtiti', 'Cockatoo']
classNames = [path.parts[-1] for path in paths]
classNames

['Bananaquit', 'Black Skimmer', 'Black Throated Bushtiti', 'Cockatoo']

python 复制代码

# 定义transforms 并处理数据
train_transforms = transforms.Compose([
    transforms.Resize([224,224]),      # 将输入图片resize成统一尺寸
    transforms.RandomHorizontalFlip(), # 随机水平翻转
    transforms.ToTensor(),             # 将PIL Image 或 numpy.ndarray 装换为tensor,并归一化到[0,1]之间
    transforms.Normalize(              # 标准化处理 --> 转换为标准正太分布（高斯分布），使模型更容易收敛
        mean = [0.485,0.456,0.406],    # 其中 mean=[0.485,0.456,0.406]与std=[0.229,0.224,0.225] 从数据集中随机抽样计算得到的。
        std = [0.229,0.224,0.225]
    )
])
test_transforms = transforms.Compose([
    transforms.Resize([224,224]),
    transforms.ToTensor(),
    transforms.Normalize(
        mean = [0.485,0.456,0.406],
        std = [0.229,0.224,0.225]
    )
])
total_data = datasets.ImageFolder('./data/bird_photos/',transform = train_transforms)
total_data

Dataset ImageFolder
    Number of datapoints: 565
    Root location: ./data/bird_photos/
    StandardTransform
Transform: Compose(
               Resize(size=[224, 224], interpolation=bilinear, max_size=None, antialias=True)
               RandomHorizontalFlip(p=0.5)
               ToTensor()
               Normalize(mean=[0.485, 0.456, 0.406], std=[0.229, 0.224, 0.225])
           )

python 复制代码

total_data.class_to_idx

{'Bananaquit': 0,
 'Black Skimmer': 1,
 'Black Throated Bushtiti': 2,
 'Cockatoo': 3}

3. 划分数据集

python 复制代码

# 划分数据集
train_size = int(len(total_data) * 0.8)
test_size = len(total_data) - train_size

train_dataset,test_dataset = torch.utils.data.random_split(total_data,[train_size,test_size])
train_dataset,test_dataset

(<torch.utils.data.dataset.Subset at 0x23b545994b0>,
 <torch.utils.data.dataset.Subset at 0x23b54599300>)

python 复制代码

# 定义DataLoader用于数据集的加载

batch_size = 32

train_dl = torch.utils.data.DataLoader(
    train_dataset,
    batch_size = batch_size,
    shuffle = True,
    num_workers = 1
)
test_dl = torch.utils.data.DataLoader(
    test_dataset,
    batch_size = batch_size,
    shuffle = True,
    num_workers = 1
)

python 复制代码

# 观察数据维度
for X,y in test_dl:
    print("Shape of X [N,C,H,W]: ",X.shape)
    print("Shape of y: ", y.shape,y.dtype)
    break

Shape of X [N,C,H,W]:  torch.Size([32, 3, 224, 224])
Shape of y:  torch.Size([32]) torch.int64

4. 模型构建部分

python 复制代码

import torch
import torch.nn as nn
import torch.nn.functional as F

class ConvBlock(nn.Module):
    def __init__(self, in_channels, filters, kernel_size, strides=1):
        super(ConvBlock, self).__init__()
        filters1, filters2, filters3 = filters

        self.conv1 = nn.Conv2d(in_channels, filters1, kernel_size=1, stride=strides)
        self.bn1 = nn.BatchNorm2d(filters1)
        self.conv2 = nn.Conv2d(filters1, filters2, kernel_size=kernel_size, padding=1)
        self.bn2 = nn.BatchNorm2d(filters2)
        self.conv3 = nn.Conv2d(filters2, filters3, kernel_size=1)
        self.bn3 = nn.BatchNorm2d(filters3)

        self.shortcut = nn.Sequential()
        if in_channels != filters3 or strides != 1:
            self.shortcut = nn.Sequential(
                nn.Conv2d(in_channels, filters3, kernel_size=1, stride=strides),
                nn.BatchNorm2d(filters3)
            )
        
    def forward(self, x):
        shortcut = self.shortcut(x)

        x = F.relu(self.bn1(self.conv1(x)))
        x = F.relu(self.bn2(self.conv2(x)))
        x = self.bn3(self.conv3(x))

        x += shortcut
        x = F.relu(x)
        return x

class ResNet50(nn.Module):
    def __init__(self, num_classes=1000):
        super(ResNet50, self).__init__()
        self.pad = nn.ZeroPad2d(3)
        self.conv1 = nn.Conv2d(3, 64, kernel_size=7, stride=2, padding=3)
        self.bn1 = nn.BatchNorm2d(64)
        self.maxpool = nn.MaxPool2d(kernel_size=3, stride=2, padding=1)

        # Define block layers with appropriate strides and filter sizes
        self.layer1 = self._build_layer(64, [64, 64, 256], blocks=3, strides=1)
        self.layer2 = self._build_layer(256, [128, 128, 512], blocks=4, strides=2)
        self.layer3 = self._build_layer(512, [256, 256, 1024], blocks=6, strides=2)
        self.layer4 = self._build_layer(1024, [512, 512, 2048], blocks=3, strides=2)

        self.avgpool = nn.AdaptiveAvgPool2d((1, 1))
        self.fc = nn.Linear(2048, num_classes)

    def _build_layer(self, in_channels, filters, blocks, strides=1):
        layers = []
        # Add the first block with potential downsampling (by strides)
        layers.append(ConvBlock(in_channels, filters, kernel_size=3, strides=strides))
        in_channels = filters[-1]
        # Add the additional blocks in this layer without downsampling
        for _ in range(1, blocks):
            layers.append(ConvBlock(in_channels, filters, kernel_size=3, strides=1))
        return nn.Sequential(*layers)

    def forward(self, x):
        x = self.pad(x)
        x = F.relu(self.bn1(self.conv1(x)))
        x = self.maxpool(x)
        x = self.layer1(x)
        x = self.layer2(x)
        x = self.layer3(x)
        x = self.layer4(x)
        x = self.avgpool(x)
        x = torch.flatten(x, 1)
        x = self.fc(x)
        return x

# Ensure the model uses the correct device
device = torch.device("cuda" if torch.cuda.is_available() else "cpu")
model = ResNet50()
model.to(device)

ResNet50(
  (pad): ZeroPad2d((3, 3, 3, 3))
  (conv1): Conv2d(3, 64, kernel_size=(7, 7), stride=(2, 2), padding=(3, 3))
  (bn1): BatchNorm2d(64, eps=1e-05, momentum=0.1, affine=True, track_running_stats=True)
  (maxpool): MaxPool2d(kernel_size=3, stride=2, padding=1, dilation=1, ceil_mode=False)
  (layer1): Sequential(
    (0): ConvBlock(
      (conv1): Conv2d(64, 64, kernel_size=(1, 1), stride=(1, 1))
      (bn1): BatchNorm2d(64, eps=1e-05, momentum=0.1, affine=True, track_running_stats=True)
      (conv2): Conv2d(64, 64, kernel_size=(3, 3), stride=(1, 1), padding=(1, 1))
      (bn2): BatchNorm2d(64, eps=1e-05, momentum=0.1, affine=True, track_running_stats=True)
      (conv3): Conv2d(64, 256, kernel_size=(1, 1), stride=(1, 1))
      (bn3): BatchNorm2d(256, eps=1e-05, momentum=0.1, affine=True, track_running_stats=True)
      (shortcut): Sequential(
        (0): Conv2d(64, 256, kernel_size=(1, 1), stride=(1, 1))
        (1): BatchNorm2d(256, eps=1e-05, momentum=0.1, affine=True, track_running_stats=True)
      )
    )
    (1): ConvBlock(
      (conv1): Conv2d(256, 64, kernel_size=(1, 1), stride=(1, 1))
      (bn1): BatchNorm2d(64, eps=1e-05, momentum=0.1, affine=True, track_running_stats=True)
      (conv2): Conv2d(64, 64, kernel_size=(3, 3), stride=(1, 1), padding=(1, 1))
      (bn2): BatchNorm2d(64, eps=1e-05, momentum=0.1, affine=True, track_running_stats=True)
      (conv3): Conv2d(64, 256, kernel_size=(1, 1), stride=(1, 1))
      (bn3): BatchNorm2d(256, eps=1e-05, momentum=0.1, affine=True, track_running_stats=True)
      (shortcut): Sequential()
    )
    (2): ConvBlock(
      (conv1): Conv2d(256, 64, kernel_size=(1, 1), stride=(1, 1))
      (bn1): BatchNorm2d(64, eps=1e-05, momentum=0.1, affine=True, track_running_stats=True)
      (conv2): Conv2d(64, 64, kernel_size=(3, 3), stride=(1, 1), padding=(1, 1))
      (bn2): BatchNorm2d(64, eps=1e-05, momentum=0.1, affine=True, track_running_stats=True)
      (conv3): Conv2d(64, 256, kernel_size=(1, 1), stride=(1, 1))
      (bn3): BatchNorm2d(256, eps=1e-05, momentum=0.1, affine=True, track_running_stats=True)
      (shortcut): Sequential()
    )
  )
  (layer2): Sequential(
    (0): ConvBlock(
      (conv1): Conv2d(256, 128, kernel_size=(1, 1), stride=(2, 2))
      (bn1): BatchNorm2d(128, eps=1e-05, momentum=0.1, affine=True, track_running_stats=True)
      (conv2): Conv2d(128, 128, kernel_size=(3, 3), stride=(1, 1), padding=(1, 1))
      (bn2): BatchNorm2d(128, eps=1e-05, momentum=0.1, affine=True, track_running_stats=True)
      (conv3): Conv2d(128, 512, kernel_size=(1, 1), stride=(1, 1))
      (bn3): BatchNorm2d(512, eps=1e-05, momentum=0.1, affine=True, track_running_stats=True)
      (shortcut): Sequential(
        (0): Conv2d(256, 512, kernel_size=(1, 1), stride=(2, 2))
        (1): BatchNorm2d(512, eps=1e-05, momentum=0.1, affine=True, track_running_stats=True)
      )
    )
    (1): ConvBlock(
      (conv1): Conv2d(512, 128, kernel_size=(1, 1), stride=(1, 1))
      (bn1): BatchNorm2d(128, eps=1e-05, momentum=0.1, affine=True, track_running_stats=True)
      (conv2): Conv2d(128, 128, kernel_size=(3, 3), stride=(1, 1), padding=(1, 1))
      (bn2): BatchNorm2d(128, eps=1e-05, momentum=0.1, affine=True, track_running_stats=True)
      (conv3): Conv2d(128, 512, kernel_size=(1, 1), stride=(1, 1))
      (bn3): BatchNorm2d(512, eps=1e-05, momentum=0.1, affine=True, track_running_stats=True)
      (shortcut): Sequential()
    )
    (2): ConvBlock(
      (conv1): Conv2d(512, 128, kernel_size=(1, 1), stride=(1, 1))
      (bn1): BatchNorm2d(128, eps=1e-05, momentum=0.1, affine=True, track_running_stats=True)
      (conv2): Conv2d(128, 128, kernel_size=(3, 3), stride=(1, 1), padding=(1, 1))
      (bn2): BatchNorm2d(128, eps=1e-05, momentum=0.1, affine=True, track_running_stats=True)
      (conv3): Conv2d(128, 512, kernel_size=(1, 1), stride=(1, 1))
      (bn3): BatchNorm2d(512, eps=1e-05, momentum=0.1, affine=True, track_running_stats=True)
      (shortcut): Sequential()
    )
    (3): ConvBlock(
      (conv1): Conv2d(512, 128, kernel_size=(1, 1), stride=(1, 1))
      (bn1): BatchNorm2d(128, eps=1e-05, momentum=0.1, affine=True, track_running_stats=True)
      (conv2): Conv2d(128, 128, kernel_size=(3, 3), stride=(1, 1), padding=(1, 1))
      (bn2): BatchNorm2d(128, eps=1e-05, momentum=0.1, affine=True, track_running_stats=True)
      (conv3): Conv2d(128, 512, kernel_size=(1, 1), stride=(1, 1))
      (bn3): BatchNorm2d(512, eps=1e-05, momentum=0.1, affine=True, track_running_stats=True)
      (shortcut): Sequential()
    )
  )
  (layer3): Sequential(
    (0): ConvBlock(
      (conv1): Conv2d(512, 256, kernel_size=(1, 1), stride=(2, 2))
      (bn1): BatchNorm2d(256, eps=1e-05, momentum=0.1, affine=True, track_running_stats=True)
      (conv2): Conv2d(256, 256, kernel_size=(3, 3), stride=(1, 1), padding=(1, 1))
      (bn2): BatchNorm2d(256, eps=1e-05, momentum=0.1, affine=True, track_running_stats=True)
      (conv3): Conv2d(256, 1024, kernel_size=(1, 1), stride=(1, 1))
      (bn3): BatchNorm2d(1024, eps=1e-05, momentum=0.1, affine=True, track_running_stats=True)
      (shortcut): Sequential(
        (0): Conv2d(512, 1024, kernel_size=(1, 1), stride=(2, 2))
        (1): BatchNorm2d(1024, eps=1e-05, momentum=0.1, affine=True, track_running_stats=True)
      )
    )
    (1): ConvBlock(
      (conv1): Conv2d(1024, 256, kernel_size=(1, 1), stride=(1, 1))
      (bn1): BatchNorm2d(256, eps=1e-05, momentum=0.1, affine=True, track_running_stats=True)
      (conv2): Conv2d(256, 256, kernel_size=(3, 3), stride=(1, 1), padding=(1, 1))
      (bn2): BatchNorm2d(256, eps=1e-05, momentum=0.1, affine=True, track_running_stats=True)
      (conv3): Conv2d(256, 1024, kernel_size=(1, 1), stride=(1, 1))
      (bn3): BatchNorm2d(1024, eps=1e-05, momentum=0.1, affine=True, track_running_stats=True)
      (shortcut): Sequential()
    )
    (2): ConvBlock(
      (conv1): Conv2d(1024, 256, kernel_size=(1, 1), stride=(1, 1))
      (bn1): BatchNorm2d(256, eps=1e-05, momentum=0.1, affine=True, track_running_stats=True)
      (conv2): Conv2d(256, 256, kernel_size=(3, 3), stride=(1, 1), padding=(1, 1))
      (bn2): BatchNorm2d(256, eps=1e-05, momentum=0.1, affine=True, track_running_stats=True)
      (conv3): Conv2d(256, 1024, kernel_size=(1, 1), stride=(1, 1))
      (bn3): BatchNorm2d(1024, eps=1e-05, momentum=0.1, affine=True, track_running_stats=True)
      (shortcut): Sequential()
    )
    (3): ConvBlock(
      (conv1): Conv2d(1024, 256, kernel_size=(1, 1), stride=(1, 1))
      (bn1): BatchNorm2d(256, eps=1e-05, momentum=0.1, affine=True, track_running_stats=True)
      (conv2): Conv2d(256, 256, kernel_size=(3, 3), stride=(1, 1), padding=(1, 1))
      (bn2): BatchNorm2d(256, eps=1e-05, momentum=0.1, affine=True, track_running_stats=True)
      (conv3): Conv2d(256, 1024, kernel_size=(1, 1), stride=(1, 1))
      (bn3): BatchNorm2d(1024, eps=1e-05, momentum=0.1, affine=True, track_running_stats=True)
      (shortcut): Sequential()
    )
    (4): ConvBlock(
      (conv1): Conv2d(1024, 256, kernel_size=(1, 1), stride=(1, 1))
      (bn1): BatchNorm2d(256, eps=1e-05, momentum=0.1, affine=True, track_running_stats=True)
      (conv2): Conv2d(256, 256, kernel_size=(3, 3), stride=(1, 1), padding=(1, 1))
      (bn2): BatchNorm2d(256, eps=1e-05, momentum=0.1, affine=True, track_running_stats=True)
      (conv3): Conv2d(256, 1024, kernel_size=(1, 1), stride=(1, 1))
      (bn3): BatchNorm2d(1024, eps=1e-05, momentum=0.1, affine=True, track_running_stats=True)
      (shortcut): Sequential()
    )
    (5): ConvBlock(
      (conv1): Conv2d(1024, 256, kernel_size=(1, 1), stride=(1, 1))
      (bn1): BatchNorm2d(256, eps=1e-05, momentum=0.1, affine=True, track_running_stats=True)
      (conv2): Conv2d(256, 256, kernel_size=(3, 3), stride=(1, 1), padding=(1, 1))
      (bn2): BatchNorm2d(256, eps=1e-05, momentum=0.1, affine=True, track_running_stats=True)
      (conv3): Conv2d(256, 1024, kernel_size=(1, 1), stride=(1, 1))
      (bn3): BatchNorm2d(1024, eps=1e-05, momentum=0.1, affine=True, track_running_stats=True)
      (shortcut): Sequential()
    )
  )
  (layer4): Sequential(
    (0): ConvBlock(
      (conv1): Conv2d(1024, 512, kernel_size=(1, 1), stride=(2, 2))
      (bn1): BatchNorm2d(512, eps=1e-05, momentum=0.1, affine=True, track_running_stats=True)
      (conv2): Conv2d(512, 512, kernel_size=(3, 3), stride=(1, 1), padding=(1, 1))
      (bn2): BatchNorm2d(512, eps=1e-05, momentum=0.1, affine=True, track_running_stats=True)
      (conv3): Conv2d(512, 2048, kernel_size=(1, 1), stride=(1, 1))
      (bn3): BatchNorm2d(2048, eps=1e-05, momentum=0.1, affine=True, track_running_stats=True)
      (shortcut): Sequential(
        (0): Conv2d(1024, 2048, kernel_size=(1, 1), stride=(2, 2))
        (1): BatchNorm2d(2048, eps=1e-05, momentum=0.1, affine=True, track_running_stats=True)
      )
    )
    (1): ConvBlock(
      (conv1): Conv2d(2048, 512, kernel_size=(1, 1), stride=(1, 1))
      (bn1): BatchNorm2d(512, eps=1e-05, momentum=0.1, affine=True, track_running_stats=True)
      (conv2): Conv2d(512, 512, kernel_size=(3, 3), stride=(1, 1), padding=(1, 1))
      (bn2): BatchNorm2d(512, eps=1e-05, momentum=0.1, affine=True, track_running_stats=True)
      (conv3): Conv2d(512, 2048, kernel_size=(1, 1), stride=(1, 1))
      (bn3): BatchNorm2d(2048, eps=1e-05, momentum=0.1, affine=True, track_running_stats=True)
      (shortcut): Sequential()
    )
    (2): ConvBlock(
      (conv1): Conv2d(2048, 512, kernel_size=(1, 1), stride=(1, 1))
      (bn1): BatchNorm2d(512, eps=1e-05, momentum=0.1, affine=True, track_running_stats=True)
      (conv2): Conv2d(512, 512, kernel_size=(3, 3), stride=(1, 1), padding=(1, 1))
      (bn2): BatchNorm2d(512, eps=1e-05, momentum=0.1, affine=True, track_running_stats=True)
      (conv3): Conv2d(512, 2048, kernel_size=(1, 1), stride=(1, 1))
      (bn3): BatchNorm2d(2048, eps=1e-05, momentum=0.1, affine=True, track_running_stats=True)
      (shortcut): Sequential()
    )
  )
  (avgpool): AdaptiveAvgPool2d(output_size=(1, 1))
  (fc): Linear(in_features=2048, out_features=1000, bias=True)
)

5. 设置超参数：定义损失函数，学习率，以及根据学习率定义优化器等

python 复制代码

# loss_fn = nn.CrossEntropyLoss() # 创建损失函数

# learn_rate = 1e-3 # 初始学习率
# def adjust_learning_rate(optimizer,epoch,start_lr):
#     # 每两个epoch 衰减到原来的0.98
#     lr = start_lr * (0.92 ** (epoch//2))
#     for param_group in optimizer.param_groups:
#         param_group['lr'] = lr
        
# optimizer = torch.optim.Adam(model.parameters(),lr=learn_rate)

python 复制代码

# 调用官方接口示例
loss_fn = nn.CrossEntropyLoss()

learn_rate = 1e-4
lambda1 = lambda epoch:(0.92**(epoch//2))

optimizer = torch.optim.Adam(model.parameters(),lr = learn_rate)
scheduler = torch.optim.lr_scheduler.LambdaLR(optimizer,lr_lambda=lambda1) # 选定调整方法

6. 训练函数

python 复制代码

# 训练函数
def train(dataloader,model,loss_fn,optimizer):
    size = len(dataloader.dataset) # 训练集大小
    num_batches = len(dataloader) # 批次数目
    
    train_loss,train_acc = 0,0
    
    for X,y in dataloader:
        X,y = X.to(device),y.to(device)
        
        # 计算预测误差
        pred = model(X)
        loss = loss_fn(pred,y)
        
        # 反向传播
        optimizer.zero_grad()
        loss.backward()
        optimizer.step()
        
        # 记录acc与loss
        train_acc += (pred.argmax(1)==y).type(torch.float).sum().item()
        train_loss += loss.item()
        
    train_acc /= size
    train_loss /= num_batches
    
    return train_acc,train_loss

7. 测试函数

python 复制代码

# 测试函数
def test(dataloader,model,loss_fn):
    size = len(dataloader.dataset)
    num_batches = len(dataloader)
    
    test_acc,test_loss = 0,0
    
    with torch.no_grad():
        for X,y in dataloader:
            X,y = X.to(device),y.to(device)
            
            # 计算loss
            pred = model(X)
            loss = loss_fn(pred,y)
            
            test_acc += (pred.argmax(1)==y).type(torch.float).sum().item()
            test_loss += loss.item()
            
    test_acc /= size
    test_loss /= num_batches
    
    return test_acc,test_loss

7. 正式训练

python 复制代码

import copy

epochs = 40

train_acc = []
train_loss = []
test_acc = []
test_loss = []

best_acc = 0.0

for epoch in range(epochs):
    
    # 更新学习率------使用自定义学习率时使用
    # adjust_learning_rate(optimizer,epoch,learn_rate)
    
    model.train()
    epoch_train_acc,epoch_train_loss = train(train_dl,model,loss_fn,optimizer)
    scheduler.step() # 更新学习率------调用官方动态学习率时使用
    
    model.eval()
    epoch_test_acc,epoch_test_loss = test(test_dl,model,loss_fn)
    
    # 保存最佳模型到 best_model
    if epoch_test_acc > best_acc:
        best_acc = epoch_test_acc
        best_model = copy.deepcopy(model)
    
    train_acc.append(epoch_train_acc)
    train_loss.append(epoch_train_loss)
    test_acc.append(epoch_test_acc)
    test_loss.append(epoch_test_loss)
    
    # 获取当前学习率
    lr = optimizer.state_dict()['param_groups'][0]['lr']
    
    template = ('Epoch:{:2d},Train_acc:{:.1f}%,Train_loss:{:.3f},Test_acc:{:.1f}%,Test_loss:{:.3f},Lr:{:.2E}')
    print(template.format(epoch+1,epoch_train_acc*100,epoch_train_loss,epoch_test_acc*100,epoch_test_loss,lr))

print('Done')

Epoch: 1,Train_acc:35.4%,Train_loss:3.431,Test_acc:23.9%,Test_loss:3.033,Lr:1.00E-04
Epoch: 2,Train_acc:69.2%,Train_loss:0.899,Test_acc:26.5%,Test_loss:3.017,Lr:9.20E-05
Epoch: 3,Train_acc:74.1%,Train_loss:0.652,Test_acc:59.3%,Test_loss:1.278,Lr:9.20E-05
Epoch: 4,Train_acc:78.3%,Train_loss:0.587,Test_acc:67.3%,Test_loss:1.353,Lr:8.46E-05
Epoch: 5,Train_acc:82.5%,Train_loss:0.521,Test_acc:75.2%,Test_loss:0.829,Lr:8.46E-05
Epoch: 6,Train_acc:86.3%,Train_loss:0.433,Test_acc:66.4%,Test_loss:1.308,Lr:7.79E-05
Epoch: 7,Train_acc:90.3%,Train_loss:0.340,Test_acc:67.3%,Test_loss:1.600,Lr:7.79E-05
Epoch: 8,Train_acc:89.2%,Train_loss:0.374,Test_acc:71.7%,Test_loss:1.014,Lr:7.16E-05
Epoch: 9,Train_acc:88.7%,Train_loss:0.305,Test_acc:77.0%,Test_loss:0.841,Lr:7.16E-05
Epoch:10,Train_acc:90.7%,Train_loss:0.309,Test_acc:79.6%,Test_loss:1.094,Lr:6.59E-05
Epoch:11,Train_acc:91.8%,Train_loss:0.318,Test_acc:72.6%,Test_loss:0.976,Lr:6.59E-05
Epoch:12,Train_acc:93.6%,Train_loss:0.243,Test_acc:73.5%,Test_loss:1.209,Lr:6.06E-05
Epoch:13,Train_acc:94.7%,Train_loss:0.159,Test_acc:71.7%,Test_loss:0.947,Lr:6.06E-05
Epoch:14,Train_acc:98.0%,Train_loss:0.076,Test_acc:80.5%,Test_loss:0.707,Lr:5.58E-05
Epoch:15,Train_acc:97.8%,Train_loss:0.083,Test_acc:79.6%,Test_loss:0.923,Lr:5.58E-05
Epoch:16,Train_acc:98.2%,Train_loss:0.059,Test_acc:82.3%,Test_loss:0.650,Lr:5.13E-05
Epoch:17,Train_acc:98.5%,Train_loss:0.072,Test_acc:76.1%,Test_loss:0.828,Lr:5.13E-05
Epoch:18,Train_acc:98.0%,Train_loss:0.175,Test_acc:78.8%,Test_loss:0.834,Lr:4.72E-05
Epoch:19,Train_acc:94.2%,Train_loss:0.173,Test_acc:61.9%,Test_loss:2.606,Lr:4.72E-05
Epoch:20,Train_acc:96.2%,Train_loss:0.123,Test_acc:77.9%,Test_loss:0.959,Lr:4.34E-05
Epoch:21,Train_acc:96.5%,Train_loss:0.166,Test_acc:76.1%,Test_loss:1.266,Lr:4.34E-05
Epoch:22,Train_acc:96.9%,Train_loss:0.196,Test_acc:85.0%,Test_loss:0.698,Lr:4.00E-05
Epoch:23,Train_acc:98.7%,Train_loss:0.082,Test_acc:82.3%,Test_loss:0.626,Lr:4.00E-05
Epoch:24,Train_acc:96.0%,Train_loss:0.136,Test_acc:81.4%,Test_loss:0.805,Lr:3.68E-05
Epoch:25,Train_acc:98.5%,Train_loss:0.101,Test_acc:83.2%,Test_loss:0.576,Lr:3.68E-05
Epoch:26,Train_acc:98.5%,Train_loss:0.062,Test_acc:80.5%,Test_loss:0.597,Lr:3.38E-05
Epoch:27,Train_acc:99.6%,Train_loss:0.039,Test_acc:83.2%,Test_loss:0.574,Lr:3.38E-05
Epoch:28,Train_acc:99.3%,Train_loss:0.080,Test_acc:85.0%,Test_loss:0.758,Lr:3.11E-05
Epoch:29,Train_acc:99.6%,Train_loss:0.059,Test_acc:84.1%,Test_loss:0.608,Lr:3.11E-05
Epoch:30,Train_acc:98.9%,Train_loss:0.054,Test_acc:82.3%,Test_loss:0.753,Lr:2.86E-05
Epoch:31,Train_acc:98.9%,Train_loss:0.035,Test_acc:83.2%,Test_loss:0.617,Lr:2.86E-05
Epoch:32,Train_acc:98.7%,Train_loss:0.046,Test_acc:78.8%,Test_loss:0.847,Lr:2.63E-05
Epoch:33,Train_acc:98.9%,Train_loss:0.028,Test_acc:82.3%,Test_loss:0.746,Lr:2.63E-05
Epoch:34,Train_acc:99.6%,Train_loss:0.032,Test_acc:79.6%,Test_loss:0.629,Lr:2.42E-05
Epoch:35,Train_acc:99.3%,Train_loss:0.027,Test_acc:82.3%,Test_loss:0.597,Lr:2.42E-05
Epoch:36,Train_acc:99.6%,Train_loss:0.029,Test_acc:87.6%,Test_loss:0.488,Lr:2.23E-05
Epoch:37,Train_acc:99.6%,Train_loss:0.026,Test_acc:87.6%,Test_loss:0.552,Lr:2.23E-05
Epoch:38,Train_acc:99.1%,Train_loss:0.029,Test_acc:79.6%,Test_loss:0.572,Lr:2.05E-05
Epoch:39,Train_acc:99.8%,Train_loss:0.107,Test_acc:84.1%,Test_loss:0.704,Lr:2.05E-05
Epoch:40,Train_acc:99.1%,Train_loss:0.094,Test_acc:76.1%,Test_loss:0.772,Lr:1.89E-05
Done

9. 结果可视化

python 复制代码

epochs_range = range(epochs)

plt.figure(figsize = (12,3))

plt.subplot(1,2,1)
plt.plot(epochs_range,train_acc,label = 'Training Accuracy')
plt.plot(epochs_range,test_acc,label = 'Test Accuracy')
plt.legend(loc = 'lower right')
plt.title('Training and Validation Accuracy')

plt.subplot(1,2,2)
plt.plot(epochs_range,train_loss,label = 'Test Accuracy')
plt.plot(epochs_range,test_loss,label = 'Test Loss')
plt.legend(loc = 'lower right')
plt.title('Training and validation Loss')
plt.show()

10. 模型的保存

python 复制代码

# 自定义模型保存
# 状态字典保存
torch.save(model.state_dict(),'./模型参数/J1_resnet50_model_state_dict.pth') # 仅保存状态字典

# 加载状态字典到模型
best_model = ResNet50().to(device) # 定义官方vgg16模型用来加载参数

best_model.load_state_dict(torch.load('./模型参数/J1_resnet50_model_state_dict.pth')) # 加载状态字典到模型

<All keys matched successfully>

11. 使用训练好的模型进行预测

python 复制代码

# 指定路径图片预测
from PIL import Image
import torchvision.transforms as transforms

classes = list(total_data.class_to_idx) # classes = list(total_data.class_to_idx)

def predict_one_image(image_path,model,transform,classes):
    
    test_img = Image.open(image_path).convert('RGB')
    # plt.imshow(test_img) # 展示待预测的图片
    
    test_img = transform(test_img)
    img = test_img.to(device).unsqueeze(0)
    
    model.eval()
    output = model(img)
    print(output) # 观察模型预测结果的输出数据
    
    _,pred = torch.max(output,1)
    pred_class = classes[pred]
    print(f'预测结果是:{pred_class}')

python 复制代码

# 预测训练集中的某张照片
predict_one_image(image_path='./data/bird_photos/Bananaquit/007.jpg',
                 model = model,
                 transform = test_transforms,
                 classes = classes
                 )

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       device='cuda:0', grad_fn=<AddmmBackward0>)
预测结果是:Bananaquit

python 复制代码

classes

['Bananaquit', 'Black Skimmer', 'Black Throated Bushtiti', 'Cockatoo']

python 复制代码

深度学习每周学习总结J1（ResNet-50算法实战与解析 - 鸟类识别）

目录

0. 总结

1. 设置GPU

2. 导入数据及处理部分

3. 划分数据集

4. 模型构建部分

5. 设置超参数：定义损失函数，学习率，以及根据学习率定义优化器等

6. 训练函数

7. 测试函数

7. 正式训练

9. 结果可视化

10. 模型的保存

11. 使用训练好的模型进行预测