import torch.nn as nn import torch.nn.functional as F class Net(nn.Module): def __init__(self): #nn.Module子类的函数必须在构造函数中执行父类的构造函数 #下式等价于nn.Module.__init__(self) super(Net,self).__init__() # 卷积层‘1’表示输入图片为单通道，‘6’表示输出通道数，‘5’表示卷积核为5*5 self.conv1 = nn.Conv2d(1,6,5) #卷积层 self.conv2 = nn.Conv2d(6*1*1,16,5) #仿射层/全连接层，y = wx + b self.fc1 = nn.Linear(16*5*5,120)#输入是16不能改变，5应该是自己定义的卷积核 self.fc2 = nn.Linear(120,84) self.fc3 = nn.Linear(84,10) def forward(self, x): # 卷积 ->激活 -> 池化 x = F.max_pool2d(F.relu(self.conv1(x)),(2,2)) x = F.max_pool2d(F.relu(self.conv2(x)),2) #reshape, '-1'表示自适应 x = x.view(x.size()[0],-1) x = F.relu(self.fc1(x)) x = F.relu(self.fc2(x)) x = self.fc3(x) return x net = Net() print(net)
__
Net(
(conv1): Conv2d(1, 6, kernel_size=(5, 5), stride=(1, 1))
(conv2): Conv2d(6, 16, kernel_size=(5, 5), stride=(1, 1))
(fc1): Linear(in_features=400, out_features=120, bias=True)
(fc2): Linear(in_features=120, out_features=84, bias=True)
(fc3): Linear(in_features=84, out_features=10, bias=True)
)
——
CIFAR-10分类
下载数据集：
import torch as t import torchvision as tv import torchvision.transforms as transforms from torchvision.transforms import ToPILImage show = ToPILImage() #可以把Tensor 转成Image,方便可视化 #第一次运行torchvision 会自动下载CIFAR-10数据集 #定义对数据的预处理 transform = transforms.Compose([ transforms.ToTensor, # 转为Tensor transforms.Normalize((0.5,0.5,0.5),(0.5,0.5,0.5)), #归一化 ]) #训练集 trainset = tv.datasets.CIFAR10( root='./data', train=True, download=True, transform=transform ) trainloader = t.utils.data.DataLoader( trainset, batch_size=4, shuffle=True, num_workers=2 ) #测试集 testset = tv.datasets.CIFAR10( './data', train=False, download=True, transform=transform ) testloader = t.utils.data.DataLoader( testset, batch_size=4, shuffle=False, num_workers=2 ) classes = ( 'plane','car','bird','cat','deer','dog','frog','horse','ship','truck' )
——
需要翻墙，不然下载非常的慢
Downloading https://www.cs.toronto.edu/~kriz/cifar-10-python.tar.gz to ./datacifar-10-python.tar.gz
Files already downloaded and verified
——
全代码：
在CPU上训练，训练了5个epoch，准确率大概在60%，时间在170s左右
windows上不支持多线程
import torch as t import torchvision as tv import torchvision.transforms as transforms from torchvision.transforms import ToPILImage import numpy as np import matplotlib.pyplot as plt show = ToPILImage() #可以把Tensor 转成Image,方便可视化 #第一次运行torchvision 会自动下载CIFAR-10数据集 #定义对数据的预处理 transform = transforms.Compose([ transforms.ToTensor(), # 转为Tensor transforms.Normalize((0.5,0.5,0.5),(0.5,0.5,0.5)), #归一化 ]) #训练集 trainset = tv.datasets.CIFAR10( root='./data', train=True, download=True, transform=transform ) #注意windows现在还不支持多线程，所以num_workers=0 trainloader = t.utils.data.DataLoader( trainset, batch_size=4, shuffle=True, num_workers=0 ) #测试集 testset = tv.datasets.CIFAR10( './data', train=False, download=True, transform=transform ) testloader = t.utils.data.DataLoader( testset, batch_size=4, shuffle=False, num_workers=0 ) classes = ( 'plane','car','bird','cat','deer','dog','frog','horse','ship','truck' ) (data,label) = trainset[100] print(classes[label]) # （data+1)/2是为了还原被归一化的数据 show((data+1)/2).resize((100,100)) # dataiter=iter(trainloader) # images,labels=dataiter.next() # print(''.join('11%s'%classes[labels[j]] for j in range(4))) # show(tv.utils.make_grid(images+1)/2).resize((400,100)) def imshow(img): img = img / 2 + 0.5 npimg = img.numpy() plt.imshow(np.transpose(npimg, (1, 2, 0))) dataiter = iter(trainloader) images, labels = dataiter.next() print(images.size()) imshow(tv.utils.make_grid(images)) plt.show()#关掉图片才能往后继续算 #卷积网络 import torch.nn as nn import torch.nn.functional as F class Net(nn.Module): def __init__(self): super(Net,self).__init__() self.conv1 = nn.Conv2d(3,6,5) self.conv2 = nn.Conv2d(6,16,5) self.fc1 = nn.Linear(16*5*5,120) self.fc2 = nn.Linear(120,84) self.fc3 = nn.Linear(84,10) def forward(self, x): x = F.max_pool2d(F.relu(self.conv1(x)),(2,2)) x = F.max_pool2d(F.relu(self.conv2(x)),2) x = x.view(x.size()[0],-1) x = F.relu(self.fc1(x)) x = F.relu(self.fc2(x)) x = self.fc3(x) return x net = Net() print(net) #损失函数和优化器 from torch import optim criterion = nn.CrossEntropyLoss()#交叉熵损失函数 optimizer = optim.SGD(net.parameters(),lr=0.001,momentum=0.9) #训练网络 from torch.autograd import Variable import time tstart = time.time() for epoch in range(5): running_loss = 0.0 for i, data in enumerate(trainloader,0): #enumerate 用法见注释 #输入数据 inputs,labels = data inputs,labels = Variable(inputs),Variable(labels) #梯度清零 optimizer.zero_grad() #forward+backward outputs = net(inputs) loss = criterion(outputs,labels) loss.backward() #更新参数 optimizer.step() #打印log（日志）信息 running_loss += loss.data[0] if i%2000 == 1999: #每2000个batch打印一次训练状态 print('[%d,%5d] loss:%.3f' %(epoch+1,i+1,running_loss/2000)) running_loss = 0.0 print('finished') tend = time.time() print('Spend time = ',tend - tstart) correct = 0 #正确数 total = 0 #总数 for data in testloader: images,labels = data outputs = net(Variable(images)) _,predicted = t.max(outputs.data,1) total += labels.size(0) correct += (predicted == labels).sum() print('%d %%' %(100*correct/total)
——
补充注释：enumerate() 函数
enumerate() 函数用于将一个可遍历的数据对象(如列表、元组或字符串)组合为一个索引序列，同时列出数据和数据下标，一般用在 for 循环当中。
Python 2.3. 以上版本可用，2.6 添加 start 参数。
语法
以下是 enumerate() 方法的语法:
enumerate(sequence, [start=0])
参数
- sequence -- 一个序列、迭代器或其他支持迭代对象。
- start -- 下标起始位置。
返回值
返回 enumerate(枚举) 对象。
实例
以下展示了使用 enumerate() 方法的实例：
>>>seasons = ['Spring', 'Summer', 'Fall', 'Winter'] >>> list(enumerate(seasons)) [(0, 'Spring'), (1, 'Summer'), (2, 'Fall'), (3, 'Winter')] >>> list(enumerate(seasons, start=1)) # 小标从 1 开始 [(1, 'Spring'), (2, 'Summer'), (3, 'Fall'), (4, 'Winter')]
——
GPU版本，跑的比CPU还慢？？
import torch as t import torchvision as tv import torchvision.transforms as transforms from torchvision.transforms import ToPILImage import numpy as np import matplotlib.pyplot as plt show = ToPILImage() #可以把Tensor 转成Image,方便可视化 #第一次运行torchvision 会自动下载CIFAR-10数据集 #定义对数据的预处理 transform = transforms.Compose([ transforms.ToTensor(), # 转为Tensor transforms.Normalize((0.5,0.5,0.5),(0.5,0.5,0.5)), #归一化 ]) #训练集 trainset = tv.datasets.CIFAR10( root='./data', train=True, download=True, transform=transform ) #注意windows现在还不支持多线程，所以num_workers=0 trainloader = t.utils.data.DataLoader( trainset, batch_size=4, shuffle=True, num_workers=0 ) #测试集 testset = tv.datasets.CIFAR10( './data', train=False, download=True, transform=transform ) testloader = t.utils.data.DataLoader( testset, batch_size=4, shuffle=False, num_workers=0 ) classes = ( 'plane','car','bird','cat','deer','dog','frog','horse','ship','truck' ) (data,label) = trainset[100] print(classes[label]) # （data+1)/2是为了还原被归一化的数据 show((data+1)/2).resize((100,100)) # dataiter=iter(trainloader) # images,labels=dataiter.next() # print(''.join('11%s'%classes[labels[j]] for j in range(4))) # show(tv.utils.make_grid(images+1)/2).resize((400,100)) def imshow(img): img = img / 2 + 0.5 npimg = img.numpy() plt.imshow(np.transpose(npimg, (1, 2, 0))) dataiter = iter(trainloader) images, labels = dataiter.next() print(images.size()) imshow(tv.utils.make_grid(images)) plt.show()#关掉图片才能往后继续算 #卷积网络 import torch.nn as nn import torch.nn.functional as F class Net(nn.Module): def __init__(self): super(Net,self).__init__() self.conv1 = nn.Conv2d(3,6,5) self.conv2 = nn.Conv2d(6,16,5) self.fc1 = nn.Linear(16*5*5,120) self.fc2 = nn.Linear(120,84) self.fc3 = nn.Linear(84,10) def forward(self, x): x = F.max_pool2d(F.relu(self.conv1(x)),(2,2)) x = F.max_pool2d(F.relu(self.conv2(x)),2) x = x.view(x.size()[0],-1) x = F.relu(self.fc1(x)) x = F.relu(self.fc2(x)) x = self.fc3(x) return x net = Net() if t.cuda.is_available(): net.cuda() print(net) #损失函数和优化器 from torch import optim criterion = nn.CrossEntropyLoss()#交叉熵损失函数 optimizer = optim.SGD(net.parameters(),lr=0.001,momentum=0.9) #训练网络 from torch.autograd import Variable import time tstart = time.time() for epoch in range(5): running_loss = 0.0 for i, data in enumerate(trainloader,0): #enumerate 用法见注释 #输入数据 inputs,labels = data inputs,labels = Variable(inputs),Variable(labels) if t.cuda.is_available(): inputs = inputs.cuda() labels = labels.cuda() #梯度清零 optimizer.zero_grad() #forward+backward outputs = net(inputs) loss = criterion(outputs,labels) loss.backward() #更新参数 optimizer.step() #打印log（日志）信息 running_loss += loss.data[0] if i%2000 == 1999: #每2000个batch打印一次训练状态 print('[%d,%5d] loss:%.3f' %(epoch+1,i+1,running_loss/2000)) running_loss = 0.0 print('finished') tend = time.time() print('Spend time = ',tend - tstart) correct = 0 #正确数 total = 0 #总数 for data in testloader: images,labels = data images = Variable(images) if t.cuda.is_available(): images = images.cuda() outputs = net(images) _,predicted = t.max(outputs.data,1) total += labels.size(0) correct += (predicted == labels.cuda()).sum() print('%d %%' %(100*correct/total))
____
CNN + MNIST
import torch from torchvision import datasets, transforms import matplotlib.pyplot as plt import os import torchvision import numpy as np from torch.autograd import Variable #数据预处理 transform = transforms.Compose([transforms.ToTensor(), transforms.Normalize(mean=[0.5,0.5,0.5],std=[0.5,0.5,0.5])]) #下载MNIST data_train = datasets.MNIST(root = "./data1", transform=transform, train = True, download = True) data_test = datasets.MNIST(root="./data1", transform = transform, train = False) data_loader_train = torch.utils.data.DataLoader(dataset=data_train, batch_size = 64, shuffle = True, num_workers=0) data_loader_test = torch.utils.data.DataLoader(dataset=data_test, batch_size = 64, shuffle = True, num_workers=0) #定义卷积网络 # 这里构建的是一个包含了卷积层和全连接层的神经网络， # 其中卷积层使用torch.nn.Conv2d来构建， # 激活层使用torch.nn.ReLU来构建， # 池化层使用torch.nn.MaxPool2d来构建， # 全连接层使用torch.nn.Linear来构建(dense) class Model(torch.nn.Module): def __init__(self): super(Model, self).__init__() self.conv1 = torch.nn.Sequential(torch.nn.Conv2d(1, 4, kernel_size=3, stride=1, padding=1), torch.nn.ReLU(), torch.nn.Conv2d(4, 16, kernel_size=3, stride=1, padding=1), torch.nn.ReLU(), torch.nn.MaxPool2d(stride=2, kernel_size=2)) # self.dense = torch.nn.Sequential(torch.nn.Linear(14 * 14 * 16, 33), #只有这个14*14不能瞎改不知道为啥 torch.nn.ReLU(), torch.nn.Dropout(p=0.5),#防止过拟合 torch.nn.Linear(33, 10)) def forward(self, x): x = self.conv1(x) # x = self.conv2(x) x = x.view(-1, 14 * 14 * 16) x = self.dense(x) return x model = Model().cuda() print(model) cost = torch.nn.CrossEntropyLoss() optimizer = torch.optim.Adam(model.parameters()) n_epochs = 5 for epoch in range(n_epochs): running_loss = 0.0 running_correct = 0 print("Epoch {}/{}".format(epoch, n_epochs)) print("-" * 10) for data in data_loader_train: X_train, y_train = data X_train, y_train = Variable(X_train).cuda(), Variable(y_train).cuda() outputs = model(X_train) _, pred = torch.max(outputs.data, 1) optimizer.zero_grad() loss = cost(outputs, y_train) loss.backward() optimizer.step() running_loss += loss.data[0] running_correct += torch.sum(pred == y_train.data) testing_correct = 0 for data in data_loader_test: X_test, y_test = data X_test, y_test = Variable(X_test).cuda(), Variable(y_test).cuda() outputs = model(X_test) _, pred = torch.max(outputs.data, 1) testing_correct += torch.sum(pred == y_test.data) print("Loss is:{:.4f}, Train Accuracy is:{:.4f}%, Test Accuracy is:{:.4f}".format(running_loss / len(data_train), 100 * running_correct / len( data_train), 100 * testing_correct / len( data_test)))
___