學習工具最快的方法就是在使用的過程中學習,也就是在工作中(解決實際問題中)學習。文章結尾處附完整代碼。
一、數據準備
在Pytorch中提供了MNIST的數據,因此我們只需要使用Pytorch提供的數據即可。
from torchvision import datasets, transforms
# batch_size 是指每次送入網絡進行訓練的數據量
batch_size = 64
# MNIST Dataset
# MNIST數據集已經集成在pytorch datasets中,可以直接調用
train_dataset = datasets.MNIST(root='./data/',
train=True,
transform=transforms.ToTensor(),
download=True)
test_dataset = datasets.MNIST(root='./data/',
train=False,
transform=transforms.ToTensor())
train_loader = torch.utils.data.DataLoader(dataset=train_dataset,
batch_size=batch_size,
shuffle=True)
test_loader = torch.utils.data.DataLoader(dataset=test_dataset,
batch_size=batch_size,
shuffle=False)
二、建立網絡
class Net(nn.Module):
def __init__(self):
super(Net, self).__init__()
# 輸入1通道,輸出10通道,kernel 5*5
self.conv1 = nn.Conv2d(in_channels=1, out_channels=10, kernel_size=5)
# 輸入10通道,輸出20通道,kernel 5*5
self.conv2 = nn.Conv2d(10, 20, 5)
# 輸入20通道,輸出40通道,kernel 3*3
self.conv3 = nn.Conv2d(20, 40, 3)
# 2*2的池化層
self.mp = nn.MaxPool2d(2)
# 全連接層(輸入特徵數,輸出)
self.fc = nn.Linear(40, 10)
def forward(self, x):
# in_size = 64
# one batch 此時的x是包含batchsize維度爲4的tensor,即(batchsize,channels,x,y)
# x.size(0)指batchsize的值,把batchsize的值作爲網絡的in_size
in_size = x.size(0)
# x: 64*1*28*28
x = F.relu(self.mp(self.conv1(x)))
# x: 64*10*12*12 (n+2p-f)/s + 1 = 28 - 5 + 1 = 24,所以在沒有池化的時候是24*24,池化層爲2*2 ,所以池化之後爲12*12
x = F.relu(self.mp(self.conv2(x)))
# x: 64*20*4*4 同理,沒有池化的時候是12 - 5 + 1 = 8 ,池化後爲4*4
x = F.relu(self.mp(self.conv3(x)))
# 輸出x : 64*40*2*2
x = x.view(in_size, -1) # 平鋪 tensor 相當於resharp
# print(x.size())
# x: 64*320
x = self.fc(x)
# x: 64*10
# print(x.size())
return F.log_softmax(x) #64*10
三、開始訓練
import torch
import torch.nn as nn
import torch.nn.functional as F
import torch.optim as optim
model = Net()
optimizer = optim.SGD(model.parameters(), lr=0.01, momentum=0.5)
def train(epoch):
# enumerate()枚舉、列舉,對於一個可迭代/遍歷的對象,enumerate將其組成一個索引序列,利用它可以同時獲得索引和值
for batch_idx, (data, target) in enumerate(train_loader): #batch_idx是enumerate()函數自帶的索引,從0開始
# data.size():[64, 1, 28, 28]
# target.size():[64]
output = model(data)
# output:64*10
loss = F.nll_loss(output, target)
# 每200次,輸出一次數據
if batch_idx % 200 == 0:
print('Train Epoch: {} [{}/{} ({:.0f}%)]\tLoss: {:.6f}'.
format(
epoch,
batch_idx * len(data),
len(train_loader.dataset),
100. * batch_idx / len(train_loader),
loss.item()))
optimizer.zero_grad() # 所有參數的梯度清零
loss.backward() # 即反向傳播求梯度
optimizer.step() # 調用optimizer進行梯度下降更新參數
# 實驗入口
for epoch in range(1, 10):
train(epoch)
對於訓練中的一些參數解釋如下:
batch_idx
:batch的索引,即batch的數量。batch_size
:每次送入網絡的數據量
四、測試模型
def test():
test_loss = 0
correct = 0
for data, target in test_loader:
data, target = Variable(data, volatile=True), Variable(target)
output = model(data.cuda())
# 累加loss
test_loss += F.nll_loss(output, target.cuda(), size_average=False).item()
# get the index of the max log-probability
# 找出每列(索引)概率意義下的最大值
pred = output.data.max(1, keepdim=True)[1]
# print(pred)
correct += pred.eq(target.data.view_as(pred).cuda()).cuda().sum()
test_loss /= len(test_loader.dataset)
print('\nTest set: Average loss: {:.4f}, Accuracy: {}/{} ({:.0f}%)\n'.format(
test_loss, correct, len(test_loader.dataset),
100. * correct / len(test_loader.dataset)))
# 實驗入口
for epoch in range(1, 10):
print("test num"+str(epoch))
train(epoch)
test()
在此展示結果的最後一次:
可以看到,我們使用SGD作爲優化器的優化函數時,測試集後來達到的正確率爲92%
五、提高測試集正確率
5.1 增加訓練次數(SGD版)
如題,我們將訓練次數增至30,優化函數仍然使用SGD,即只在入口循環處改變epoch的取值範圍。爲了節省空間,結果只輸出測試集loss和正確率。
我們可以看到,在num18時,測試集的正確率收斂,達到了96%;loss也是在0.1附近波動。
Test set: Average loss: 2.2955, Accuracy: 1018/10000 (10%)
test num1
Test set: Average loss: 2.2812, Accuracy: 2697/10000 (26%)
test num2
Test set: Average loss: 2.2206, Accuracy: 3862/10000 (38%)
test num3
Test set: Average loss: 1.8014, Accuracy: 6100/10000 (61%)
test num4
Test set: Average loss: 0.7187, Accuracy: 8049/10000 (80%)
test num5
Test set: Average loss: 0.4679, Accuracy: 8593/10000 (85%)
test num6
Test set: Average loss: 0.3685, Accuracy: 8898/10000 (88%)
test num7
Test set: Average loss: 0.3006, Accuracy: 9108/10000 (91%)
test num8
Test set: Average loss: 0.2713, Accuracy: 9177/10000 (91%)
test num9
Test set: Average loss: 0.2343, Accuracy: 9270/10000 (92%)
test num10
Test set: Average loss: 0.2071, Accuracy: 9370/10000 (93%)
test num11
Test set: Average loss: 0.1910, Accuracy: 9413/10000 (94%)
test num12
Test set: Average loss: 0.1783, Accuracy: 9453/10000 (94%)
test num13
Test set: Average loss: 0.1612, Accuracy: 9482/10000 (94%)
test num14
Test set: Average loss: 0.1603, Accuracy: 9497/10000 (94%)
test num15
Test set: Average loss: 0.1522, Accuracy: 9526/10000 (95%)
test num16
Test set: Average loss: 0.1410, Accuracy: 9555/10000 (95%)
test num17
Test set: Average loss: 0.1338, Accuracy: 9573/10000 (95%)
test num18
Test set: Average loss: 0.1307, Accuracy: 9588/10000 (95%)
test num19
Test set: Average loss: 0.1212, Accuracy: 9610/10000 (96%)
test num20
Test set: Average loss: 0.1232, Accuracy: 9622/10000 (96%)
test num21
Test set: Average loss: 0.1149, Accuracy: 9646/10000 (96%)
test num22
Test set: Average loss: 0.1104, Accuracy: 9652/10000 (96%)
test num23
Test set: Average loss: 0.1072, Accuracy: 9668/10000 (96%)
test num24
Test set: Average loss: 0.1113, Accuracy: 9646/10000 (96%)
test num25
Test set: Average loss: 0.1037, Accuracy: 9659/10000 (96%)
test num26
Test set: Average loss: 0.0970, Accuracy: 9700/10000 (97%)
test num27
Test set: Average loss: 0.1013, Accuracy: 9692/10000 (96%)
test num28
Test set: Average loss: 0.1015, Accuracy: 9675/10000 (96%)
test num29
Test set: Average loss: 0.0952, Accuracy: 9711/10000 (97%)
test num30
Test set: Average loss: 0.0885, Accuracy: 9727/10000 (97%)
Process finished with exit code 0
5.2 Adam版(訓練次數:30)
Adam還是名副其實的老大,第一次就已經達到了SGD收斂時候的loss值和正確率。我們可以看到,在num26時,Adam優化函數下的模型對於測試集的預測正確率達到了99%,loss爲0.0397,但是正確率似乎並沒有收斂到99%。
test num1
Test set: Average loss: 0.1108, Accuracy: 9660/10000 (96%)
test num2
Test set: Average loss: 0.0932, Accuracy: 9709/10000 (97%)
test num3
Test set: Average loss: 0.0628, Accuracy: 9800/10000 (98%)
test num4
Test set: Average loss: 0.0562, Accuracy: 9813/10000 (98%)
test num5
Test set: Average loss: 0.0478, Accuracy: 9832/10000 (98%)
test num6
Test set: Average loss: 0.0442, Accuracy: 9850/10000 (98%)
test num7
Test set: Average loss: 0.0386, Accuracy: 9863/10000 (98%)
test num8
Test set: Average loss: 0.0768, Accuracy: 9753/10000 (97%)
test num9
Test set: Average loss: 0.0343, Accuracy: 9879/10000 (98%)
test num10
Test set: Average loss: 0.0347, Accuracy: 9877/10000 (98%)
test num11
Test set: Average loss: 0.0494, Accuracy: 9825/10000 (98%)
test num12
Test set: Average loss: 0.0571, Accuracy: 9811/10000 (98%)
test num13
Test set: Average loss: 0.0342, Accuracy: 9887/10000 (98%)
test num14
Test set: Average loss: 0.0400, Accuracy: 9870/10000 (98%)
test num15
Test set: Average loss: 0.0339, Accuracy: 9889/10000 (98%)
test num16
Test set: Average loss: 0.0371, Accuracy: 9889/10000 (98%)
test num17
Test set: Average loss: 0.0402, Accuracy: 9872/10000 (98%)
test num18
Test set: Average loss: 0.0434, Accuracy: 9887/10000 (98%)
test num19
Test set: Average loss: 0.0377, Accuracy: 9877/10000 (98%)
test num20
Test set: Average loss: 0.0402, Accuracy: 9883/10000 (98%)
test num21
Test set: Average loss: 0.0407, Accuracy: 9886/10000 (98%)
test num22
Test set: Average loss: 0.0482, Accuracy: 9871/10000 (98%)
test num23
Test set: Average loss: 0.0414, Accuracy: 9891/10000 (98%)
test num24
Test set: Average loss: 0.0407, Accuracy: 9890/10000 (98%)
test num25
Test set: Average loss: 0.0403, Accuracy: 9898/10000 (98%)
test num26
Test set: Average loss: 0.0397, Accuracy: 9902/10000 (99%)
test num27
Test set: Average loss: 0.0491, Accuracy: 9873/10000 (98%)
test num28
Test set: Average loss: 0.0416, Accuracy: 9896/10000 (98%)
test num29
Test set: Average loss: 0.0450, Accuracy: 9897/10000 (98%)
test num30
Test set: Average loss: 0.0500, Accuracy: 9875/10000 (98%)
Process finished with exit code 0
5.3 AdaBound版(訓練次數:30)
AdaBound即最近北大、浙大本科生新提出的訓練速度比肩Adam,性能媲美SGD的優化算法。
可以看到,在num4、num5時就正確率已經達到了98%,loss已經比Adam收斂時候的loss低。而在num8的時候,正確率突破99%!loss達到了0.0303!,在接下來的幾次訓練中,正確率和loss有細微的波動,但是隨着訓練次數的增加,正確率和loss還是達到了最佳的收斂值,波動並不是特別大。
test num1
Test set: Average loss: 0.1239, Accuracy: 9614/10000 (96%)
test num2
Test set: Average loss: 0.0965, Accuracy: 9704/10000 (97%)
test num3
Test set: Average loss: 0.0637, Accuracy: 9794/10000 (97%)
test num4
Test set: Average loss: 0.0485, Accuracy: 9852/10000 (98%)
test num5
Test set: Average loss: 0.0403, Accuracy: 9870/10000 (98%)
test num6
Test set: Average loss: 0.0513, Accuracy: 9836/10000 (98%)
test num7
Test set: Average loss: 0.0446, Accuracy: 9856/10000 (98%)
test num8
Test set: Average loss: 0.0303, Accuracy: 9910/10000 (99%)
test num9
Test set: Average loss: 0.0411, Accuracy: 9873/10000 (98%)
test num10
Test set: Average loss: 0.0422, Accuracy: 9870/10000 (98%)
test num11
Test set: Average loss: 0.0319, Accuracy: 9894/10000 (98%)
test num12
Test set: Average loss: 0.0303, Accuracy: 9905/10000 (99%)
test num13
Test set: Average loss: 0.0338, Accuracy: 9897/10000 (98%)
test num14
Test set: Average loss: 0.0313, Accuracy: 9904/10000 (99%)
test num15
Test set: Average loss: 0.0285, Accuracy: 9920/10000 (99%)
test num16
Test set: Average loss: 0.0319, Accuracy: 9917/10000 (99%)
test num17
Test set: Average loss: 0.0427, Accuracy: 9884/10000 (98%)
test num18
Test set: Average loss: 0.0351, Accuracy: 9894/10000 (98%)
test num19
Test set: Average loss: 0.0337, Accuracy: 9897/10000 (98%)
test num20
Test set: Average loss: 0.0321, Accuracy: 9910/10000 (99%)
test num21
Test set: Average loss: 0.0354, Accuracy: 9908/10000 (99%)
test num22
Test set: Average loss: 0.0332, Accuracy: 9905/10000 (99%)
test num23
Test set: Average loss: 0.0347, Accuracy: 9904/10000 (99%)
test num24
Test set: Average loss: 0.0362, Accuracy: 9906/10000 (99%)
test num25
Test set: Average loss: 0.0402, Accuracy: 9900/10000 (99%)
test num26
Test set: Average loss: 0.0380, Accuracy: 9900/10000 (99%)
test num27
Test set: Average loss: 0.0378, Accuracy: 9914/10000 (99%)
test num28
Test set: Average loss: 0.0356, Accuracy: 9913/10000 (99%)
test num29
Test set: Average loss: 0.0360, Accuracy: 9912/10000 (99%)
Process finished with exit code 0
六、完整代碼
import torch
import torch.nn as nn
import torch.nn.functional as F
import torch.optim as optim
from torchvision import datasets, transforms
from torch.autograd import Variable
import adabound
# Training settings
batch_size = 64
# TODO dataset 和 dataloader
# MNIST Dataset
# MNIST數據集已經集成在pytorch datasets中,可以直接調用
train_dataset = datasets.MNIST(root='./data/',
train=True,
transform=transforms.ToTensor(),
download=True)
test_dataset = datasets.MNIST(root='./data/',
train=False,
transform=transforms.ToTensor())
# Data Loader (Input Pipeline)
train_loader = torch.utils.data.DataLoader(dataset=train_dataset,
batch_size=batch_size,
shuffle=True)
test_loader = torch.utils.data.DataLoader(dataset=test_dataset,
batch_size=batch_size,
shuffle=False)
class Net(nn.Module):
def __init__(self):
super(Net, self).__init__()
# 輸入1通道,輸出10通道,kernel 5*5
self.conv1 = nn.Conv2d(in_channels=1, out_channels=10, kernel_size=5)
self.conv2 = nn.Conv2d(10, 20, 5)
self.conv3 = nn.Conv2d(20, 40, 3)
self.mp = nn.MaxPool2d(2)
# fully connect
self.fc = nn.Linear(40, 10)#(in_features, out_features)
def forward(self, x):
# in_size = 64
# one batch 此時的x是包含batchsize維度爲4的tensor,即(batchsize,channels,x,y)
# x.size(0)指batchsize的值 把batchsize的值作爲網絡的in_size
in_size = x.size(0)
# x: 64*1*28*28
x = F.relu(self.mp(self.conv1(x)))
# x: 64*10*12*12 (n+2p-f)/s + 1 = 28 - 5 + 1 = 24,所以在沒有池化的時候是24*24,池化層爲2*2 ,所以池化之後爲12*12
x = F.relu(self.mp(self.conv2(x)))
# x: 64*20*4*4 同理,沒有池化的時候是12 - 5 + 1 = 8 ,池化後爲4*4
x = F.relu(self.mp(self.conv3(x)))
# 輸出x : 64*40*2*2
x = x.view(in_size, -1) # 平鋪 tensor 相當於resharp
# print(x.size())
# x: 64*320
x = self.fc(x)
# x:64*10
# print(x.size())
return F.log_softmax(x) #64*10
model = Net()
model.cuda()
# optimizer = optim.SGD(model.parameters(), lr=0.001, momentum=0.5)
# optimizer = adabound.AdaBound(model.parameters(), lr=1e-3, final_lr=0.1)
optimizer = optim.Adam(model.parameters(), lr=0.001)
def train(epoch):
# enumerate()枚舉、列舉,對於一個可迭代/遍歷的對象,enumerate將其組成一個索引序列,利用它可以同時獲得索引和值
for batch_idx, (data, target) in enumerate(train_loader): # batch_idx是enumerate()函數自帶的索引,從0開始
# data.size():[64, 1, 28, 28]
# target.size():[64]
output = model(data.cuda())
# print(batch_idx)
# output:64*10
loss = F.nll_loss(output, target.cuda())
# 每200次,輸出一次數據
# if batch_idx % 200 == 0:
# print('Train Epoch: {} [{}/{} ({:.0f}%)]\tLoss: {:.6f}'.
# format(
# epoch,
# batch_idx * len(data),
# len(train_loader.dataset),
# 100. * batch_idx / len(train_loader),
# loss.item()))
optimizer.zero_grad() # 所有參數的梯度清零
loss.backward() #即反向傳播求梯度
optimizer.step() #調用optimizer進行梯度下降更新參數
def test():
test_loss = 0
correct = 0
for data, target in test_loader:
data, target = Variable(data, volatile=True), Variable(target)
output = model(data.cuda())
# 累加loss
test_loss += F.nll_loss(output, target.cuda(), size_average=False).item()
# get the index of the max log-probability
# 找出每列(索引)概率意義下的最大值
pred = output.data.max(1, keepdim=True)[1]
# print(pred)
correct += pred.eq(target.data.view_as(pred).cuda()).cuda().sum()
test_loss /= len(test_loader.dataset)
print('\nTest set: Average loss: {:.4f}, Accuracy: {}/{} ({:.0f}%)\n'.format(
test_loss, correct, len(test_loader.dataset),
100. * correct / len(test_loader.dataset)))
for epoch in range(1, 30):
print("test num"+str(epoch))
train(epoch)
test()
七、參考資料及獲得的幫助
- AdaBound詳解【首發】
- 完成本次實驗得到了何樹林同學的大力支持
- 本次實驗的代碼在網上參考修改,由於不慎關閉了相關頁面……找不到出處了,如果有雷同,請及時告訴我,以便在此聲明參考出處。