keras版本鏈接

導包

import torch from torch import nn from torch import optim import torch.nn.functional as F from torch.utils.data import Dataset from torch.utils.data import DataLoader from resnets_utils import *

Dataset類

class MyDataset(Dataset):def __init__(self, x, y):super(MyDataset, self).__init__()assert x.shape[0] == y.shape[0]self.x = xself.y = ydef __len__(self):return self.x.shape[0]def __getitem__(self, item):return self.x[item], self.y[item]

Flatten類

class Flatten(nn.Module):def __init__(self, start_dim=1, end_dim=-1):super(Flatten, self).__init__()self.start_dim = start_dimself.end_dim = end_dimdef forward(self, input):return input.flatten(self.start_dim, self.end_dim)

The identity block

class IdentityBlock(nn.Module):def __init__(self, channels, f):super(IdentityBlock, self).__init__()channel1, channel2, channel3, channel4 = channelsself.conv = nn.Sequential(# nn.Conv2d(in_channels=channel1, out_channels=channel2, kernel_size=1, stride=1, padding='valid'),nn.Conv2d(in_channels=channel1, out_channels=channel2, kernel_size=1, stride=1, padding=0),nn.BatchNorm2d(num_features=channel2),nn.ReLU(),# nn.Conv2d(in_channels=channel2, out_channels=channel3, kernel_size=f, stride=1, padding='same'),nn.Conv2d(in_channels=channel2, out_channels=channel3, kernel_size=f, stride=1, padding=(f - 1) // 2),nn.BatchNorm2d(num_features=channel3),nn.ReLU(),# nn.Conv2d(in_channels=channel3, out_channels=channel4, kernel_size=1, stride=1, padding='valid'),nn.Conv2d(in_channels=channel3, out_channels=channel4, kernel_size=1, stride=1, padding=0),nn.BatchNorm2d(num_features=channel4),)def forward(self, input):x_shortcut = inputx = self.conv(input)x = x_shortcut + xx = F.relu(x)return x

The convolutional block

class ConvolutionalBlock(nn.Module):def __init__(self, channels, f, s):super(ConvolutionalBlock, self).__init__()channel1, channel2, channel3, channel4 = channelsself.conv1 = nn.Sequential(# nn.Conv2d(in_channels=channel1, out_channels=channel2, kernel_size=1, stride=s, padding='valid'),nn.Conv2d(in_channels=channel1, out_channels=channel2, kernel_size=1, stride=s, padding=0),nn.BatchNorm2d(num_features=channel2),nn.ReLU(),# nn.Conv2d(in_channels=channel2, out_channels=channel3, kernel_size=f, stride=1, padding='same'),nn.Conv2d(in_channels=channel2, out_channels=channel3, kernel_size=f, stride=1, padding=(f - 1) // 2),nn.BatchNorm2d(num_features=channel3),nn.ReLU(),# nn.Conv2d(in_channels=channel3, out_channels=channel4, kernel_size=1, stride=1, padding='valid'),nn.Conv2d(in_channels=channel3, out_channels=channel4, kernel_size=1, stride=1, padding=0),nn.BatchNorm2d(num_features=channel4))self.conv2 = nn.Sequential(# nn.Conv2d(in_channels=channel1, out_channels=channel4, kernel_size=1, stride=s, padding='valid'),nn.Conv2d(in_channels=channel1, out_channels=channel4, kernel_size=1, stride=s, padding=0),nn.BatchNorm2d(num_features=channel4))def forward(self, input):x = self.conv1(input)x_shortcut = self.conv2(input)x = x + x_shortcutx = F.relu(x)return x

ResNet50

class ResNet50(nn.Module):def __init__(self, classes=6):super(ResNet50, self).__init__()self.net = nn.Sequential(nn.ZeroPad2d(padding=(3, 3, 3, 3)),nn.Conv2d(in_channels=3, out_channels=64, kernel_size=7, stride=2, padding=0),nn.BatchNorm2d(num_features=64),nn.ReLU(),nn.MaxPool2d(kernel_size=3, stride=2),ConvolutionalBlock(channels=[64, 64, 64, 256], f=3, s=1),IdentityBlock(channels=[256, 64, 64, 256], f=3),IdentityBlock(channels=[256, 64, 64, 256], f=3),ConvolutionalBlock(channels=[256, 128, 128, 512], f=3, s=2),IdentityBlock(channels=[512, 128, 128, 512], f=3),IdentityBlock(channels=[512, 128, 128, 512], f=3),IdentityBlock(channels=[512, 128, 128, 512], f=3),ConvolutionalBlock(channels=[512, 256, 256, 1024], f=3, s=2),IdentityBlock(channels=[1024, 256, 256, 1024], f=3),IdentityBlock(channels=[1024, 256, 256, 1024], f=3),IdentityBlock(channels=[1024, 256, 256, 1024], f=3),IdentityBlock(channels=[1024, 256, 256, 1024], f=3),IdentityBlock(channels=[1024, 256, 256, 1024], f=3),ConvolutionalBlock(channels=[1024, 512, 512, 2048], f=3, s=2),IdentityBlock(channels=[2048, 512, 512, 2048], f=3),IdentityBlock(channels=[2048, 512, 512, 2048], f=3),nn.AvgPool2d(kernel_size=2),Flatten(),nn.Linear(2048, classes),)def forward(self, input):x = self.net(input)return x

加載數據集和預處理

X_train_orig, Y_train_orig, X_test_orig, Y_test_orig, classes = load_dataset()# Normalize image vectors X_train = X_train_orig / 255. X_test = X_test_orig / 255. X_train = np.transpose(X_train, [0, 3, 1, 2]) X_test = np.transpose(X_test, [0, 3, 1, 2])Y_train = Y_train_orig.T Y_test = Y_test_orig.Tprint("number of training examples = " + str(X_train.shape[0])) print("number of test examples = " + str(X_test.shape[0])) print("X_train shape: " + str(X_train.shape)) print("Y_train shape: " + str(Y_train.shape)) print("X_test shape: " + str(X_test.shape)) print("Y_test shape: " + str(Y_test.shape))

構建網絡、優化器、損失函數

model = ResNet50() optimizer = optim.Adam(model.parameters()) criterion = nn.CrossEntropyLoss() epochs = 2 batch_size = 32 train_dataset = MyDataset(X_train, Y_train) train_data = DataLoader(dataset=train_dataset, batch_size=batch_size, shuffle=True)

訓練

model.train() for epoch in range(epochs):for i, (x, y) in enumerate(train_data):x = x.float()y = y.long().squeeze()optimizer.zero_grad()y_hat = model(x)loss = criterion(y_hat, y)loss.backward()optimizer.step()

測試

model.eval() with torch.no_grad():x = torch.tensor(X_test).float()y = torch.tensor(Y_test).long().squeeze()y_hat = model(x)loss = criterion(y_hat, y)print("Loss = ", loss.item())y_hat = torch.argmax(y_hat, dim=-1)correct_prediction = y_hat == ytest_accuracy = torch.sum(correct_prediction).float() / y.shape[0]print("Test Accuracy = ", test_accuracy.item())

總結

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