本期我們來利用pytorch深度學習架構進行CIFAR-10項目實踐。從本文你将要學到
- 如何利用torchvision.datasets讀取遠端資料
CIFAR-10圖像分類項目
- 背景
- 讀取資料并可視化
- 建構網絡,損失函數,優化方式
- 模型訓練
- 評估模型
- 儲存模型
- 加載模型做測試
- 參考文獻
背景
CIFAR-10是kaggle計算機視覺競賽的一個圖像分類項目。該資料集共有60000張32*32彩色圖像,一共可以分為"plane", “car”, “bird”,“cat”, “deer”, “dog”, “frog”,“horse”,“ship”, “truck” 10類,每類6000張圖。有50000張用于訓練,構成了5個訓練批,每一批10000張圖;10000張用于測試,單獨構成一批。
import torch
import torchvision
import torchvision.transforms as transforms
transform = transforms.Compose(
[transforms.ToTensor(),
transforms.Normalize((0.5, 0.5, 0.5), (0.5, 0.5, 0.5))])
trainset = torchvision.datasets.CIFAR10(root = './data', train =True, download = True, transform = transform)
trainloader =torch.utils.data.DataLoader(trainset, batch_size =4, shuffle = True, num_workers = 0)
testset = torchvision.datasets.CIFAR10(root = './data', train = False, download = True, transform = transform)
testloader = torch.utils.data.DataLoader(testset, batch_size = 4, shuffle = False, num_workers = 0)
classes = ("plane", "car", "bird","cat", "deer", "dog", "frog","horse","ship", "truck")
import matplotlib.pyplot as plt
import numpy as np
def imShow(img):
img = img /2 + 0.5
npimg = img.numpy()
plt.imshow(np.transpose(npimg, (1,2,0)))
plt.show()
dataiter =iter(trainloader)
images, labels = dataiter.next()
imShow(torchvision.utils.make_grid(images))
print(" ".join("%5s" % classes[labels[j]] for j in range(4)))
- 輸出結果
Files already downloaded and verified
Files already downloaded and verified
truck car frog plane
import torch.nn as nn
import torch.nn.functional as F
import torch.optim as optim
class Net(nn.Module): #繼承的torch.nn.Module類
def __init__(self):
super(Net, self).__init__()
self.conv1 = nn.Conv2d(3, 6, 5) #添加第一個卷積層,調用了nn裡面的Conv2d()
self.pool = nn.MaxPool2d(2, 2) #添加最大池化層
self.conv2 = nn.Conv2d(6, 16, 5) #添加第二個卷積層
self.fc1 = nn.Linear(16*5*5, 120) #第一個全連接配接層
self.fc2 = nn.Linear(120, 84) #第二個全連接配接層
self.fc3 = nn.Linear(84, 10) #第三個全連接配接層
def forward(self, x): #定義向前傳播方法
x = self.pool(F.relu(self.conv1(x))) #relu激活第一個卷積層
x = self.pool(F.relu(self.conv2(x))) #relu激活第二個卷積層
x = x.view(-1, 16*5*5) #重構張量的次元
x = F.relu(self.fc1(x))
x = F.relu(self.fc2(x))
x = self.fc3(x)
return x
net = Net() #網絡執行個體化
criterion = nn.CrossEntropyLoss() #定義損失函數為交叉熵損失函數
optimizer = optim.SGD(net.parameters(), lr = 0.001, momentum = 0.9) #定義優化方式為機梯度下降
for epoch in range(2):
running_loss =0.0
for i, data in enumerate(trainloader, 0):
inputs, labels = data
optimizer.zero_grad()
outputs = net(inputs)
loss = criterion(outputs, labels)
loss.backward()
optimizer.step()
running_loss += loss.item()
if i%2000 == 1999:
print('[%d, %5d] loss: %.3f' % (epoch + 1, i + 1, running_loss / 2000))
running_loss = 0.0
print("Finished Training")
correct = 0
total = 0
with torch.no_grad():
for data in testloader:
images, labels =data
outputs = net(images)
_, predicted = torch.max(outputs.data, 1)
total += labels.size(0)
correct +=(predicted==labels).sum().item()
print('Accuracy of the network on the 10000 test images: %d %%' % (100 * correct / total))
class_correct = list(0. for i in range(10))
class_total = list(0. for i in range(10))
with torch.no_grad():
for data in testloader:
images, labels = data
outputs = net(images)
_, predicted = torch.max(outputs, 1)
c = (predicted == labels).squeeze()
for i in range(4):
label = labels[i]
class_correct[label] += c[i].item()
class_total[label] += 1
for i in range(10):
print('Accuracy of %5s : %2d %%' % (
classes[i], 100 * class_correct[i] / class_total[i]))
PATH =".cifar10_net.pth"
torch.save(net.state_dict(), PATH)
net = Net()
net.load_state_dict(torch.load(PATH))
outputs = net(images)
_, predicted = torch.max(outputs, 1)
print("predicted: ", " ".join("%5s" % classes[predicted[j]] for j in range(4)))