小土堆pytorch学习笔记

  想入门pytorch强化学习，就去找pytorch的课来看。B站上播放量最高的就是小土堆的课，整体跟下来感觉内容还是很详细的，但和我的预期不太一样，这个是DL的不是RL的，不过作为对于pytorch使用的初期了解也是很好的，这篇博客就把整个学习过程做一个梳理。
  注意：本笔记使用的数据集全部都是CIFAR10，下载比较简单~，下面开始

数据读取

  在读取之前，需要先准备好数据了，对于CIFAR10,可以离线下载(网址：https://download.pytorch.org/tutorial/hymenoptera_data.zip)，下载后保存到dataset文件夹，目录结构如下：

  下面就是对于图片的读取，起初的读取都是通过PIL，后面会换成dataloader，主要是自己定义了一个类，传递了两个参数，实例如下：

  read_data.py

# function：使用PIL完成数据的读取，可查看
from torch.utils.data import Dataset
from PIL import Image
import os

class MyData(Dataset):
    def __init__(self, root_dir, label_dir):
        self.root_dir = root_dir
        self.label_dir = label_dir
        self.path = os.path.join(self.root_dir, self.label_dir)
        self.img_path = os.listdir(self.path)

    def __getitem__(self, idx):
        img_name = self.img_path[idx]
        img_item_path = os.path.join(self.root_dir, self.label_dir, img_name)
        img = Image.open(img_item_path)
        img.show()
        label = self.label_dir
        return img, label

    def __len__(self):
        return len(self.img_path)

root_dir = "dataset/train"
ants_label_dir = "ants"
ants_datasets = MyData(root_dir, ants_label_dir)
ants_datasets.__getitem__(0)   # 输入查看图片编号即可
print(len(ants_datasets))
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28

tensorboard使用

  tensorboard是一个可视化工具，可以用来看图片或者分析数据。
  先说一下安装，在安装的时候报了两个错：

报错：ModuleNotFoundError: No module named 'tensorboard'
解决：pip install tensorboard -i http://mirrors.aliyun.com/pypi/simple --trusted-host mirrors.aliyun.com

报错：ModuleNotFoundError: No module named 'six'
解决：pip install six -i http://mirrors.aliyun.com/pypi/simple --trusted-host mirrors.aliyun.com
1
2
3
4
5

  使用方法：

  1.按照主要模板写框架：

from torch.utils.tensorboard import SummaryWriter

writer = SummaryWriter("logs")   # 这个logs是生成日志文件的文件夹名，可随意更换
writer.add_image()	   # 添加一张图像，第一个参数是tag，第二个是数据本身，第三个是编号
wirter.add_images()	# 添加多张图像，第一个是tag，第二个是数据本身，第三个是编号
writer.add_scalar()    # 添加数值 第一个参数是tag, 再后是先y后x, 例如：writer.add_scalar("y=2x", 2*i, i)  
writer.add_graph(tudui, input)   # 查看网络结构，tudui是模型，input是模型输入
writer.close()
1
2
3
4
5
6
7
8

  执行代码过后就会在logs文件夹下生成event文件：

  2.在terminal中按照tensorboard --logdir=logs使用：

  3.点进localhost的链接中就可以查看了：

  还可以看网络结构：

test_tb.py

# function：展示tensorboard的使用
from torch.utils.tensorboard import SummaryWriter
import numpy as np
from PIL import Image

writer = SummaryWriter("logs")

# add_image使用
image_path = "dataset/train/ants/5650366_e22b7e1065.jpg"
image_path1 = "dataset/train/ants/6240329_72c01e663e.jpg"
img_PIL = Image.open(image_path)
img_array = np.array(img_PIL)
img_PIL1 = Image.open(image_path1)
img_array1 = np.array(img_PIL1)
writer.add_image("image", img_array, 1, dataformats='HWC')   # 这个通道顺序需要改，tensorboard默认使用的是tensor结构，但这个读的是PIL结构
writer.add_image("image", img_array1, 2, dataformats='HWC')

# add_scalar使用
# for i in range(100):
#     writer.add_scalar("y=2x", 2*i, i)
writer.close()
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21

transforms使用

  transforms是用来进行数据类型的转换，pytorch中使用的数据格式大多是Tensor，transfroms直接提供了工具

  transforms_learn.py

# function：展示transforms的基本使用格式
from PIL import Image
from torch.utils.tensorboard import SummaryWriter
from torchvision import transforms
import numpy as np

writer = SummaryWriter("logs")

# python用法 → tensor数据类型
# 通过transform.ToTensor看两个问题
    # 1. transform如何使用
    # 2. 为什么需要Tensor
image_path = "dataset/train/ants/522163566_fec115ca66.jpg"
# PIL → Tensor()
img = Image.open(image_path)
tensor_trans = transforms.ToTensor()
tensor_img = tensor_trans(img)

writer.add_image("image", tensor_img, 1)
writer.close()
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20

  useful_transforms.py

  有几个常见的transforms，可以记一下使用方法：ToTensor(转换为Tensor类型)，Normalize(做正则化)，Resize(调整数据shape)，Compose(将多个transfroms整合在一起)，RandomCrop(随机裁剪数据)，使用方式如下：

# function：展示部分常见transfroms，包括：ToTensor(转换为Tensor类型)，Normalize(做正则化)，Resize(调整数据shape)，Compose(将多个transfroms整合在一起)，RandomCrop(随机裁剪数据)
from PIL import Image
from torch.utils.tensorboard import SummaryWriter
from torchvision import transforms

writer = SummaryWriter("logs")
img = Image.open("dataset/train/ants/5650366_e22b7e1065.jpg")

# ToTensor
trans_totensor = transforms.ToTensor()
img_tensor = trans_totensor(img)

# Normalize
trans_norm = transforms.Normalize([0.5, 0.5, 0.5], [0.5, 0.5, 0.5])
img_norm = trans_norm(img_tensor)

# Resize
# 输入序列(512, 512)或者数值(512, 会生成方阵)
trans_resize = transforms.Resize((512, 512))
img_resize = trans_resize(img)
img_resize = trans_totensor(img_resize)

# Compose
# PIL → PIL → tensor
trans_resize_2 = transforms.Resize(512)
trans_compose = transforms.Compose([trans_resize_2, trans_totensor])
img_resize_2 = trans_compose(img)

# RandomCrop——随机裁剪
trans_ramdom = transforms.RandomCrop(128)
trans_compose_2 = transforms.Compose([trans_ramdom, trans_totensor])
for i in range(10):
    img_crop = trans_compose_2(img)
    writer.add_image("RandomCrop", img_crop, i)

writer.add_image("ToTensor", img_tensor, 1)
writer.add_image("Norm", img_norm, 2)
writer.add_image("Resize", img_resize, 3)
writer.add_image("Compose", img_resize_2, 4)
writer.close()
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40

  dataset_transforms.py

  这个主要开始使用dataLoader进行数据提取了，因为图片数据直接是PIL类型，所以在dataloader的时候就要进行transforms。datasets来源于torchversion：
    torchversion：可以下载默认数据集
    torchvision：dataset 下载数据集
    torchvision：dataloader 选择特定数据下载
  使用方式如下：

import torchvision
from torch.utils.tensorboard import SummaryWriter
from torch.utils.data import DataLoader

# # ====torchvision.datasets使用====
# dataset_transform = torchvision.transforms.Compose([torchvision.transforms.ToTensor()])
# train_set = torchvision.datasets.CIFAR10(root="./dataset", train=True, transform=dataset_transform, download=True)
# test_set = torchvision.datasets.CIFAR10(root="./dataset", train=False, transform=dataset_transform, download=True)
#
# writer = SummaryWriter("dataset_transformer")
# for i in range(10):
#     img, target = train_set[i]
#     writer.add_image("test_set", img, i)
# writer.close()

# # ====torchvision.DataLoader使用====
test_data = torchvision.datasets.CIFAR10("./dataset", train=False, transform=torchvision.transforms.Compose([torchvision.transforms.ToTensor()]))
test_loader = DataLoader(dataset=test_data, batch_size=64, shuffle=True, num_workers=0, drop_last=True)

img, target = test_data[0]
print(img.shape)
print(target)

step = 0
writer = SummaryWriter("dataloader")
for data in test_loader:
    imgs, targets = data
    writer.add_images("dataloader", imgs, step) # 注意：批量添加的时候使用add_images函数
    step = step + 1
writer.close()
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30

torch.nn使用

  torch.nn是pytorch对于神经网络(neural network)提供的有关操作支持，具体的东西有很多，只讲解了一部分常用的

  conv2d

  卷积操作的实现(具体啥是卷积，视频里解释的很详细)，我在这里就留个模板了：

  nn_conv2d.py

# torch.nn 的卷积conv2d 实例
import torch
import torchvision
from torch import nn
from torch.nn import Conv2d
from torch.utils.data import DataLoader
from torch.utils.tensorboard import SummaryWriter

dataset = torchvision.datasets.CIFAR10("./dataset", train=False, transform=torchvision.transforms.ToTensor(), download=True)
dataLoader = DataLoader(dataset, batch_size=64)

class Tudui(nn.Module):
    def __init__(self):
        super(Tudui, self).__init__()
        self.conv1 = Conv2d(in_channels=3, out_channels=6, kernel_size=3, stride=1, padding=0)

    def forward(self, x):
        x = self.conv1(x)
        return x

tudui = Tudui()
step = 0
writter = SummaryWriter("logs_conv2d")
for data in dataLoader:
    imgs, targets = data
    output = tudui(imgs)
    writter.add_images("input", imgs, step)
    output = torch.reshape(output, [-1, 3, 30, 30])
    writter.add_images("output", output, step)
    step = step + 1
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30

  nn.module基本使用

  上面的Tudui类继承了nn.module，其实这个是整体pytorch关于神经网络的父类，使用时继承就好了，留一个简单的模板：

  nn_module.py

# function：nn.module的基本使用
import torch
from torch import nn
class Tudui(nn.Module):
    # 注意父类写的格式
    def __init__(self):
        super().__init__()

    def forward(self, input):
        output = input + 1
        return output

tudui = Tudui()
x = torch.tensor(1.0)
output = tudui(x)
print(output)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16

  maxpool.py

    最大池化和卷积区别
    卷积是利用卷积核做计算，维度不变
    卷积是利用卷积核计算后取最大值，维度不变
  最大池化的实现：

# function：torch.nn 最大池化maxpool示例
import torch
import torchvision
from torch import nn
from torch.nn import MaxPool2d
from torch.utils.data import DataLoader
from torch.utils.tensorboard import SummaryWriter

dataset = torchvision.datasets.CIFAR10("./dataset", download=True, train=False, transform=torchvision.transforms.ToTensor())
dataLoader = DataLoader(dataset, batch_size=64)

input = torch.tensor([[1, 2, 0, 3, 1],
                      [0, 1, 2, 3, 1],
                      [1, 2, 1, 0, 0],
                      [5, 2, 5, 1, 1],
                      [2, 1, 0, 1, 2]
                      ], dtype=torch.float32)
input = torch.reshape(input, (-1, 1, 5, 5))
print(input.shape)

class Tudui(nn.Module):
    def __init__(self):
        super(Tudui, self).__init__()
        # ceil_mode为True，保留边框部分(多)
        # ceil_mode为False，不保留边框部分(少)
        self.maxpool = MaxPool2d(kernel_size=3, ceil_mode=False)

    def forward(self, input):
        output = self.maxpool(input)
        return output

writer = SummaryWriter("log_maxpool")
tudui = Tudui()
output = tudui(input)
step = 0
for data in dataLoader:
    imgs, targets = data
    writer.add_images("intput", imgs, step)
    output = tudui(imgs)
    writer.add_images("output", output, step)
    step = step + 1
writer.close()
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42

  linear.py

  线性化的实现：

import torch
import torchvision
from torch import nn
from torch.nn import Linear
from torch.utils.data import DataLoader

dataset = torchvision.datasets.CIFAR10("./dataset", download=True, train=False, transform=torchvision.transforms.ToTensor())
dataLoader = DataLoader(dataset, batch_size=64)

class Tudui(nn.Module):
    def __init__(self):
        super(Tudui, self).__init__()
        self.Linear = Linear(196608, 10)
    def forward(self, input):
        output = self.Linear(input)
        return output

tudui = Tudui()
for data in dataLoader:
    imgs, targets = data
    print(imgs.shape)
    output = torch.flatten(imgs)
    print(output.shape)
    output = tudui(output)
    print(output.shape)

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26

  loss

  loss是损失函数，pytorch中提供了几种可以直接使用的，我在这里直接举例了：

  nn_loss.py

# function：损失函数使用示例
import torch
from torch.nn import L1Loss
from torch import nn

inputs = torch.tensor([1, 2, 3], dtype=torch.float32)
targets = torch.tensor([1, 2, 5], dtype=torch.float32)

inputs = torch.reshape(inputs, (1, 1, 1, 3))
targets = torch.reshape(targets, (1, 1, 1, 3))

# L1直接损失
loss = L1Loss()
result = loss(inputs, targets)

# 均方差损失
loss_mse = nn.MSELoss()
result_mes = loss_mse(inputs, targets)

x = torch.tensor([0.1, 0.2, 0.3])
y = torch.tensor([1])
x = torch.reshape(x, (1, 3))
loss_cross = nn.CrossEntropyLoss()
result_cross = loss_cross(x, y)
print(result)
print(result_mes)
print(result_cross)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27

  optimal

  优化器的使用，有个模板：

        optim.zero_grad()        # 1.设置梯度为0
        result_loss.backward()   # 2.计算梯度，进行反向传播
        optim.step()             # 3.进行梯度更新，调整权重参数(降低loss)
1
2
3

  示例如下：

  nn_optimal.py

import torch
import torchvision
from torch import nn
from torch.nn import Conv2d, Linear, Sequential
from torch.nn import MaxPool2d
from torch.nn import Flatten
from torch.utils.data import DataLoader, dataloader
from nn_loss import loss

class Tudui(nn.Module):
    def __init__(self):
        super(Tudui, self).__init__()
        self.model = Sequential(
            Conv2d(3, 32, 5, padding=2),
            MaxPool2d(2),
            Conv2d(32, 32, 5, padding=2),
            MaxPool2d(2),
            Conv2d(32, 64, 5, padding=2),
            MaxPool2d(2),
            Flatten(),
            Linear(1024, 64),
            Linear(64, 10)
        )

    def forward(self, input):
        x = self.model(input)
        return x

dataset = torchvision.datasets.CIFAR10("./dataset", train=False, transform=torchvision.transforms.ToTensor(), download=True)
dataLoader = DataLoader(dataset, batch_size=1)

loss = nn.CrossEntropyLoss()
tudui = Tudui()
optim = torch.optim.SGD(tudui.parameters(), lr=0.01)
for epoch in range(20):
    running_loss = 0.0
    for data in dataLoader:
        imgs, targets = data
        outputs = tudui(imgs)
        result_loss = loss(outputs, targets)
        optim.zero_grad()        # 1.设置梯度为0
        result_loss.backward()   # 2.计算梯度，进行反向传播
        optim.step()             # 3.进行梯度更新，调整权重参数(降低loss)
        running_loss = running_loss + result_loss
    print(running_loss)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45

  relu.py

  引入非线性(线性的表彰不好)，示例如下：

import torch
import torchvision
from torch import nn
from torch.nn import ReLU
from torch.utils.data import DataLoader
from torch.utils.tensorboard import SummaryWriter

input = torch.tensor([[1, 0.5],
                      [-1, 3]])
input = torch.reshape(input, (-1, 1, 2, 2))
print(input)

dataset = torchvision.datasets.CIFAR10("./dataset", download=True, train=False, transform=torchvision.transforms.ToTensor())
dataLoader = DataLoader(dataset, batch_size=64)

class Tudui(nn.Module):
    def __init__(self):
        super(Tudui, self).__init__()
        self.relu = ReLU()
    def forward(self, input):
        output = self.relu(input)
        return output
writer = SummaryWriter("logs_relu")
tudui = Tudui()
output = tudui(input)
step = 0
for data in dataLoader:
    imgs, targets = data
    writer.add_images("input", imgs, step)
    output = tudui(imgs)
    writer.add_images("output", output, step)
    step = step + 1
writer.close()

print(output)

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36

  sequential.py

  传统方式写模型，要在forward中一层一层写 结构。使用sequential可以直接在model中进行定义，示例如下：

## 传统方式：自己写模型
# import torch
# from torch import nn
# from torch.nn import Conv2d, Linear, Sequential
# from torch.nn import MaxPool2d
# from torch.nn import Flatten
#
# class Tudui(nn.Module):
#     def __init__(self):
#         super(Tudui, self).__init__()
#         self.conv1 = Conv2d(3, 32, 5, padding=2)
#         self.maxpool1 = MaxPool2d(2)
#         self.conv2 = Conv2d(32, 32, 5, padding=2)
#         self.maxpool2 = MaxPool2d(2)
#         self.conv3 = Conv2d(32, 64, 5, padding=2)
#         self.maxpool3 = MaxPool2d(2)
#         self.flatten = Flatten()
#         self.linear1 = Linear(1024, 64)
#         self.linear2 = Linear(64, 10)
#
#     def forward(self, input):
#         x = self.conv1(input)
#         x = self.maxpool1(x)
#         x = self.conv2(x)
#         x = self.maxpool2(x)
#         x = self.conv3(x)
#         x = self.maxpool3(x)
#         x = self.flatten(x)
#         x = self.linear1(x)
#         x = self.linear2(x)
#         return x
#
# tudui = Tudui()
# input = torch.ones((64, 3, 32, 32))
# output = tudui(input)
# print(output.shape)

## 使用Sequential写模型
import torch
from torch import nn
from torch.nn import Conv2d, Linear, Sequential
from torch.nn import MaxPool2d
from torch.nn import Flatten
from torch.utils.tensorboard import SummaryWriter


class Tudui(nn.Module):
    def __init__(self):
        super(Tudui, self).__init__()
        self.model = Sequential(
            Conv2d(3, 32, 5, padding=2),
            MaxPool2d(2),
            Conv2d(32, 32, 5, padding=2),
            MaxPool2d(2),
            Conv2d(32, 64, 5, padding=2),
            MaxPool2d(2),
            Flatten(),
            Linear(1024, 64),
            Linear(64, 10)
        )

    def forward(self, input):
        x = self.model(input)
        return x

writer = SummaryWriter("logs_sequential")
tudui = Tudui()
input = torch.ones((64, 3, 32, 32))
output = tudui(input)
writer.add_graph(tudui, input)
writer.close()
print(output.shape)
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72

整体模型训练

  train_cpu.py

  示例如下：

import torchvision
from torch.utils.data import DataLoader
import torch
from torch import  nn
from torch.utils.tensorboard import SummaryWriter

train_data = torchvision.datasets.CIFAR10("./dataset", train=True, download=True, transform=torchvision.transforms.ToTensor())
test_data = torchvision.datasets.CIFAR10("./dataset", train=False, download=True, transform=torchvision.transforms.ToTensor())


# length
train_data_size = len(train_data)
test_data_size = len(test_data)
print("训练数据集长度为：{}".format(train_data_size))
print("测试数据集长度为：{}".format(test_data_size))

# 利用dataloader来加载数据集
train_dataloader = DataLoader(train_data, batch_size=64)
test_dataloader = DataLoader(test_data, batch_size=64)

# 搭建神经网络
class Tudui(nn.Module):
    def __init__(self):
        super(Tudui, self).__init__()
        self.model = nn.Sequential(
            nn.Conv2d(3, 32, 5, 1, 2),
            nn.MaxPool2d(2),
            nn.Conv2d(32, 32, 5, 1, 2),
            nn.MaxPool2d(2),
            nn.Conv2d(32, 64, 5, 1, 2),
            nn.MaxPool2d(2),
            nn.Flatten(),
            nn.Linear(64*4*4, 64),
            nn.Linear(64, 10))
    def forward(self, input):
        x = self.model(input)
        return x

### 测试模型正确性
# if __name__ == '__main__':
#     tudui = Tudui()
#     input = torch.ones((64, 3, 32, 32))
#     output = tudui(input)
#     print(output.shape)

# 创建网络模型
tudui = Tudui()

# 损失函数
loss_fn = nn.CrossEntropyLoss()

# 优化器
learning_rate = 1e-2
optimizer = torch.optim.SGD(tudui.parameters(), lr=learning_rate)

# 设置训练网络的一些参数
total_train_step = 0
total_test_step = 0
# 训练轮数
epoch = 10

# 添加tensorboard
writter = SummaryWriter("logs_train")

total_test_step = 0
for i in range(10):
    print("-----第{}轮训练开始----".format(i+1))
    # 训练步骤开始
    tudui.train()   #特定层：Dropout
    for data in train_dataloader:
        # 1. 数据导入
        imgs, targets = data
        # 2. 模型导入
        outputs = tudui(imgs)
        # 3. loss计算
        loss = loss_fn(outputs, targets)
        # 4. 优化器优化模型
        optimizer.zero_grad()
        loss.backward()
        optimizer.step()

        total_train_step = total_train_step + 1
        if total_train_step % 100 == 0:
            print("训练次数：{}, loss:{}".format(total_train_step, loss.item()))  #loss.item()相当于取值
            writter.add_scalar("train_loss", loss.item(), total_train_step)
    # 测试步骤开始
    tudui.eval()
    total_test_loss = 0
    total_accuracy = 0
    with torch.no_grad():
        for data in test_dataloader:
            imgs, targets = data
            outputs = tudui(imgs)
            loss = loss_fn(outputs, targets)
            total_test_loss = total_test_loss + loss.item()
            accuracy = (outputs.argmax(1) == targets).sum()
            total_accuracy = total_accuracy + accuracy
    print("整体测试集上的loss:{}".format(total_test_loss))
    print("整体测试集上的正确率：{}".format(total_accuracy/test_data_size))
    writter.add_scalar("test_loss", loss.item(), total_test_step)
    writter.add_scalar("test_accuracy", total_accuracy/test_data_size, total_test_step)
    total_test_step = total_test_step + 1

    # 保存训练模型
    torch.save(tudui, "tudui_{}.pth".format(i))
    print("模型已保存！")
writter.close()

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108

  train_gpu.py

  示例如下：

# 与CPU的区别：在网络模型、数据、损失函数上增加cuda()

import torchvision
from torch.utils.data import DataLoader
import torch
from torch import  nn
from torch.utils.tensorboard import SummaryWriter

train_data = torchvision.datasets.CIFAR10("./dataset", train=True, download=True, transform=torchvision.transforms.ToTensor())
test_data = torchvision.datasets.CIFAR10("./dataset", train=False, download=True, transform=torchvision.transforms.ToTensor())


# length
train_data_size = len(train_data)
test_data_size = len(test_data)
print("训练数据集长度为：{}".format(train_data_size))
print("测试数据集长度为：{}".format(test_data_size))

# 利用dataloader来加载数据集
train_dataloader = DataLoader(train_data, batch_size=64)
test_dataloader = DataLoader(test_data, batch_size=64)

# 搭建神经网络
class Tudui(nn.Module):
    def __init__(self):
        super(Tudui, self).__init__()
        self.model = nn.Sequential(
            nn.Conv2d(3, 32, 5, 1, 2),
            nn.MaxPool2d(2),
            nn.Conv2d(32, 32, 5, 1, 2),
            nn.MaxPool2d(2),
            nn.Conv2d(32, 64, 5, 1, 2),
            nn.MaxPool2d(2),
            nn.Flatten(),
            nn.Linear(64*4*4, 64),
            nn.Linear(64, 10))
    def forward(self, input):
        x = self.model(input)
        return x

### 测试模型正确性
# if __name__ == '__main__':
#     tudui = Tudui()
#     input = torch.ones((64, 3, 32, 32))
#     output = tudui(input)
#     print(output.shape)

# 创建网络模型
tudui = Tudui()
tudui = Tudui().cuda()

# 损失函数
loss_fn = nn.CrossEntropyLoss()
loss_fn = loss_fn.cuda()

# 优化器
learning_rate = 1e-2
optimizer = torch.optim.SGD(tudui.parameters(), lr=learning_rate)


# 设置训练网络的一些参数
total_train_step = 0
total_test_step = 0
# 训练轮数
epoch = 10

# 添加tensorboard
writter = SummaryWriter("logs_train")

total_test_step = 0
for i in range(10):
    print("-----第{}轮训练开始----".format(i+1))
    # 训练步骤开始
    tudui.train()   #特定层：Dropout
    for data in train_dataloader:
        # 1. 数据导入
        imgs, targets = data
        imgs = imgs.cuda()
        targets = targets.cuda()
        # 2. 模型导入
        outputs = tudui(imgs)
        # 3. loss计算
        loss = loss_fn(outputs, targets)
        # 4. 优化器优化模型
        optimizer.zero_grad()
        loss.backward()
        optimizer.step()

        total_train_step = total_train_step + 1
        if total_train_step % 100 == 0:
            print("训练次数：{}, loss:{}".format(total_train_step, loss.item()))  #loss.item()相当于取值
            writter.add_scalar("train_loss", loss.item(), total_train_step)
    # 测试步骤开始
    tudui.eval()
    total_test_loss = 0
    total_accuracy = 0
    with torch.no_grad():
        for data in test_dataloader:
            imgs, targets = data
            imgs = imgs.cuda()
            targets = targets.cuda()
            outputs = tudui(imgs)
            loss = loss_fn(outputs, targets)
            total_test_loss = total_test_loss + loss.item()
            accuracy = (outputs.argmax(1) == targets).sum()
            total_accuracy = total_accuracy + accuracy
    print("整体测试集上的loss:{}".format(total_test_loss))
    print("整体测试集上的正确率：{}".format(total_accuracy/test_data_size))
    writter.add_scalar("test_loss", loss.item(), total_test_step)
    writter.add_scalar("test_accuracy", total_accuracy/test_data_size, total_test_step)
    total_test_step = total_test_step + 1

    # 保存训练模型
    torch.save(tudui, "tudui_{}.pth".format(i))
    print("模型已保存！")
writter.close()

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117

模型保存

  model_save.py

  示例如下：

# function：训练模型的保存
import torch
import torchvision

vgg16 = torchvision.models.vgg16(pretrained=False)

# 保存方式1
torch.save(vgg16, "vgg16_method1.pth")

# 保存方式2(官方推荐)
torch.save(vgg16.state_dict(), "vgg16_method2.pth")
1
2
3
4
5
6
7
8
9
10
11

模型加载

  model_loader

  示例如下：

# function：现有模型加载

import torch
import torchvision

model = torch.load("vgg16_method1.pth")
print(model)

vgg16 = torchvision.models.vgg16(pretrained=False)
vgg16.load_state_dict(torch.load("vgg16_method2.pth"))
# model = torch.load("vgg16_method2.pth")  # 直接是字典权重
print(model)
1
2
3
4
5
6
7
8
9
10
11
12

模型使用

  model_use.py

  示例如下：

# function：自找图片，验证train.py训练的模型准确性
import torch
import  torchvision
from PIL import Image
from torch import nn

image_path = "dog.png"
image = Image.open(image_path)

transform = torchvision.transforms.Compose([torchvision.transforms.Resize((32, 32)), torchvision.transforms.ToTensor()])

image = transform(image)

class Tudui(nn.Module):
    def __init__(self):
        super(Tudui, self).__init__()
        self.model = nn.Sequential(
            nn.Conv2d(3, 32, 5, 1, 2),
            nn.MaxPool2d(2),
            nn.Conv2d(32, 32, 5, 1, 2),
            nn.MaxPool2d(2),
            nn.Conv2d(32, 64, 5, 1, 2),
            nn.MaxPool2d(2),
            nn.Flatten(),
            nn.Linear(64*4*4, 64),
            nn.Linear(64, 10))
    def forward(self, input):
        x = self.model(input)
        return x

model = torch.load("tudui_9.pth")
image = torch.reshape(image, (1, 3, 32, 32))
image = image.cuda()
model.eval()
with torch.no_grad():
    output = model(image)
print(output.argmax(1))
1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37

预模型使用

  premodel_use.py

  示例如下：

# function：使用现有网络对现有数据集进行训练
import torchvision
from torch import nn

vgg16_false = torchvision.models.vgg16(pretrained=False)
vgg16_true = torchvision.models.vgg16(pretrained=True)
print(vgg16_true)

train_data = torchvision.datasets.CIFAR10("./dataset", train=True, download=True, transform=torchvision.transforms.ToTensor())
# CIFAR10最终的输出结果是10类，所以必须按照原来的增加一层
vgg16_true.classifier.add_module('add_linear', nn.Linear(1000, 10))
print(vgg16_true)

# CIFAR10最终的输出结果是10类，也可以在原来基础上做改动
vgg16_false.classifier[6] = nn.Linear(4096, 10)
print(vgg16_false)

1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17

  以上简单的了解了下pytorch的基础，学习仍在继续，继续加油~