【pytorchでニューラルネットワーク#9】CNN

投稿者 Dken2021年9月30日2021年9月30日

記事の目的

pytorchでCNN(畳み込みニューラルネットワーク)を実装していきます。ここにある全てのコードは、コピペで再現することが可能です。

目次

ライブラリとデータ
モデル
モデルの学習と評価

1 ライブラリとデータ

# In[1]
from torchvision import datasets
import torchvision.transforms as transforms
from torch.utils.data import DataLoader

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

import matplotlib.pyplot as plt

torch.manual_seed(1)

# In[2]
transform = transforms.Compose([transforms.ToTensor(),transforms.Normalize((0),(1))])

root = './data2'
mnist_train = datasets.MNIST(root=root,download=True,train=True,transform=transform)
mnist_test = datasets.MNIST(root=root,download=True,train=False,transform=transform)

train_dataloader = DataLoader(mnist_train,batch_size=100,shuffle=True)
test_dataloader = DataLoader(mnist_test,batch_size=100,shuffle=False)

# In[3]
x, t = next(iter(train_dataloader))
image = x[0,].view(28,28).detach().numpy()
plt.imshow(image,cmap='binary_r')

2 モデル

# In[4]
class Model(nn.Module):
    def __init__(self):
        super().__init__()
        self.c1 = nn.Conv2d(1, 32, kernel_size=4, stride=2, padding=1)
        self.b1 = nn.BatchNorm2d(32)
        self.c2 = nn.Conv2d(32, 64, kernel_size=4, stride=2, padding=1)
        self.b2 = nn.BatchNorm2d(64)
        self.l1 = nn.Linear(576,128)
        self.b3 = nn.BatchNorm1d(128)
        self.l2 = nn.Linear(128,10)
    def forward(self,x):
        x = torch.relu(self.b1(self.c1(x)))
        x = F.max_pool2d(torch.relu(self.b2(self.c2(x))),2)
        x = x.view(-1,576)
        x = torch.relu(self.b3(self.l1(x)))
        x = self.l2(x)
        return x

# In[5]
model = Model()
criterion = nn.CrossEntropyLoss()
optimizer = optim.SGD(model.parameters(),lr=1e-2)

3 モデルの学習と評価

# In[6]
loss_train_all = []
acc_train_all = []
loss_test_all = []
acc_test_all = []

for epoch in range(1, 20+1):
    
    loss_train = 0
    acc_train = 0
    loss_test = 0
    acc_test = 0
    
    model.train()
    for (x,t) in train_dataloader:
        y = model(x)
        loss = criterion(y,t)
        optimizer.zero_grad()
        loss.backward()
        optimizer.step()
        
        loss_train += loss.item()
        acc_train += sum(y.argmax(axis=1) == t)/len(t)
        
    loss_train_mean = loss_train / len(train_dataloader)
    acc_train_mean = acc_train / len(train_dataloader)
    
    model.eval()
    with torch.no_grad():
        for x, t in test_dataloader:
            y = model(x)
            loss = criterion(y,t)
        
            loss_test += loss.item()
            acc_test += sum(y.argmax(axis=1) == t)/len(t)
        
    loss_test_mean = loss_test / len(test_dataloader)
    acc_test_mean = acc_test / len(test_dataloader)
    
    loss_train_all.append(loss_train_mean)
    acc_train_all.append(acc_train_mean)
    loss_test_all.append(loss_test_mean)
    acc_test_all.append(acc_test_mean)
    
    if epoch == 1 or epoch % 5 == 0:
        print(f"Epoch: {epoch}")
        print(f"loss_train: {loss_train_mean:.4f}, acc_train: {acc_train_mean:.4f}")
        print(f"loss_test: {loss_test_mean:.4f}, acc_test: {acc_test_mean:.4f}")    

# In[7]
plt.plot(range(1,len(loss_train_all)+1), loss_train_all, label="train")
plt.plot(range(1,len(loss_test_all)+1), loss_test_all, label="test")
plt.legend()

# In[8]
plt.plot(range(1,len(acc_train_all)+1), acc_train_all, label="train")
plt.plot(range(1,len(acc_test_all)+1), acc_test_all, label="test")
plt.legend()