pytorch（网络模型）

Posted 2022-06-08 月屯

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神经网络鸡翅nn.Module

官网

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

class Model(nn.Module):
    def __init__(self):
        super().__init__()
        self.conv1 = nn.Conv2d(1, 20, 5)
        self.conv2 = nn.Conv2d(20, 20, 5)

    def forward(self, x):
        x = F.relu(self.conv1(x))# 卷积、非线性处理
        return F.relu(self.conv2(x))

练习

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

class Dun(nn.Module):
    def __init__(self):
        super().__init__()
        self.conv1 = nn.Conv2d(1, 20, 5)
        self.conv2 = nn.Conv2d(20, 20, 5)

    def forward(self, x):
        return x+1
dun=Dun()
x=torch.tensor(1.0)# 转化类型
output=dun(x);# 调用forward
print(output)# 输出

卷积层

import torch
input=torch.tensor([[1,2,0,3,1],
                    [0,1,2,3,1],
                    [1,2,1,0,0],
                    [5,2,3,1,1],
                    [2,1,0,1,1]])
kernel=torch.tensor([[1,2,1],
                     [0,1,0],
                     [2,1,0]])
print(input.shape)# 输出尺寸
print(kernel.shape)

input=torch.reshape(input,(1,1,5,5))# 类型转换
kernel=torch.reshape(kernel,(1,1,3,3))# 类型转换
print(input)
print(kernel)

print(input.shape)
print(kernel.shape)

# 卷积操作
out= F.conv2d(input,kernel,stride=1)
print(out)

out= F.conv2d(input,kernel,stride=2)
print(out)

# 填充
out= F.conv2d(input,kernel,stride=1,padding=1)
print(out)

输出chanel是2时

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("./data_set_test",train=False,transform=torchvision.transforms.ToTensor(),download=True)
dataloader= DataLoader(dataset,batch_size=64)

# 卷积类
class Dun(nn.Module):
    def __init__(self):
        super().__init__()
        self.conv1=Conv2d(in_channels=3,out_channels=6,kernel_size=3,stride=1,padding=0)
    def forward(self,x):
        return self.conv1(x)

dun=Dun()
print(dun)

writer= SummaryWriter("./logs")
step=0
# 卷积操作
for data in dataloader:
    img,target=data
    output=dun(img)
    print(img.shape)
    print(output.shape)
    writer.add_images("input",img,step)
    output=torch.reshape(output,(-1,3,30,30))# -1时会根据后面的值自动计算
    writer.add_images("output",output,step)
    step+=1
writer.close()

池化层

作用：就像高清视频换成低清视频

import  torch
from torch import nn
from torch.nn import MaxPool2d

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

class Dun(nn.Module):
    def __init__(self):
        super().__init__()
        self.maxpool=MaxPool2d(kernel_size=3,ceil_mode=True)# ceil_model false和True的结果和预期的一致
    def forward(self,inut):
        return self.maxpool(input)
dun=Dun()
out=dun(input)
print(out)

图片处理

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("./data_set_test",train=False,transform=torchvision.transforms.ToTensor(),download=True)
dataloader= DataLoader(dataset,batch_size=64)

class Dun(nn.Module):
    def __init__(self):
        super().__init__()
        self.maxpool=MaxPool2d(kernel_size=3,ceil_mode=True)# ceil_model false和True的结果和预期的一致
    def forward(self,input):
        return self.maxpool(input)

dun=Dun()
step=0
writer=SummaryWriter("logs")
for data in dataloader:
    img,target=data
    writer.add_images("input",img,step)
    output=dun(img)
    writer.add_images("output",output,step)
    step+=1
writer.close()

非线性激活

非线性变换目的是引入非线性特征，可以更好地处理信息

ReLU

import torch
from torch import nn
from torch.nn import ReLU

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

class Dun(nn.Module):
    def __init__(self):
        super().__init__()
        self.relu1=ReLU()
    def forward(self,input):
        return self.relu1(input)

dun=Dun()
output=dun(input)
print(output)

sigmoid

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

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

class Dun(nn.Module):
    def __init__(self):
        super().__init__()
        self.relu1=ReLU()
        self.sigmoid=Sigmoid()
    def forward(self,input):
        return self.sigmoid(input)

dun=Dun()
writer=SummaryWriter("./logs")
step=0

for data in dataloader:
    img,target=data
    writer.add_images("input",img,global_step=step)
    output=dun(img)
    writer.add_images("output",output,global_step=step)
    step+=1
writer.close()

线性层

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

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

class Dun(nn.Module):
    def __init__(self):
        super().__init__()
        self.linear=Linear(196608,10)
    def forward(self,input):
        return self.linear(input)
dun=Dun()
for data in dataloader:
    img,target=data
    print(img.shape)
#    input=torch.reshape(img,(1,1,1,-1))
    input= torch.flatten(img)# 将数据展平一行，可以代替上面的一行
    print(input.shape)
    output=dun(input)
    print(output.shape)

正则化层

加快神经网络地训练速度

# With Learnable Parameters
m = nn.BatchNorm2d(100)
# Without Learnable Parameters
m = nn.BatchNorm2d(100, affine=False)
input = torch.randn(20, 100, 35, 45)
output = m(input)

其他层有Recurrent Layers、Transformer Layers、Linear Layers等

简单的网络模型

import torch
from torch import nn
from torch.nn import Conv2d, MaxPool2d, Flatten, Linear, Sequential
from torch.utils.tensorboard import SummaryWriter


class Dun(nn.Module):
    def __init__(self):
        super().__init__()
        # 2.
        self.model1 = 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))
    # 1.
    #     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,x):
        x=self.model1(x)
        return x

dun=Dun()
# 测试
input=torch.ones((64,3,32,32))
print(dun(input).shape)

writer=SummaryWriter("./logs")
writer.add_graph(dun,input)
writer.close()

loss function

L1Loss、MSELoss

import torch
from torch.nn import L1Loss
from torch import nn
input=torch.tensor([1,2,3],dtype=torch.float32)
targrt=torch.tensor([1,2,5],dtype=torch.float32)


loss=L1Loss(reduction="sum")# 该参数有sum和mean两种，默认是mean
print(loss(input,targrt))

loss_mse=nn.MSELoss()
print(loss_mse(input,targrt))

CROSSENTROPYLOSS

import torch
from torch.nn import L1Loss
from torch import nn
x=torch.tensor([0.1,0.2,0.3])
y=torch.tensor([1])
x=torch.reshape(x,(1,3))
loss_cross=nn.CrossEntropyLoss()
print(loss_cross(x,y))

使用

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

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

# 分类神经网络
class Dun(nn.Module):
    def __init__(self):
        super().__init__()
        # 2.
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