稀疏自编码器手写
2021-12-21 22:33
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1 导入实验需要的包
import torch import torch.nn as nn import torch.nn.functional import torch.optim as optim import torch.utils.data.dataloader as dataloader import torchvision import torchvision.datasets as datasets import torchvision.transforms as transforms import os,time import matplotlib.pyplot as plt from PIL import Image
2 读取数据
def get_mnist_loader(batch_size=100, shuffle=True): """ :return: train_loader, test_loader """ train_dataset = datasets.MNIST(root='../data', train=True, transform=torchvision.transforms.ToTensor(), download=True) test_dataset = datasets.MNIST(root='../data', train=False, transform=torchvision.transforms.ToTensor(), download=True) train_loader = torch.utils.data.DataLoader(dataset=train_dataset, batch_size=batch_size, shuffle=shuffle) test_loader = torch.utils.data.DataLoader(dataset=test_dataset, batch_size=batch_size, shuffle=shuffle) return train_loader, test_loader
3 KL散度
def KL_devergence(p, q): """ Calculate the KL-divergence of (p,q) :param p: :param q: :return: """ q = torch.nn.functional.softmax(q, dim=0) q = torch.sum(q, dim=0)/batch_size # dim:缩减的维度,q的第一维是batch维,即大小为batch_size大小,此处是将第j个神经元在batch_size个输入下所有的输出取平均 s1 = torch.sum(p*torch.log(p/q)) s2 = torch.sum((1-p)*torch.log((1-p)/(1-q))) return s1+s2
4 自编码器
class AutoEncoder(nn.Module): def __init__(self, in_dim=784, hidden_size=30, out_dim=784): super(AutoEncoder, self).__init__() self.encoder = nn.Sequential( nn.Linear(in_features=in_dim, out_features=hidden_size), nn.ReLU() ) self.decoder = nn.Sequential( nn.Linear(in_features=hidden_size, out_features=out_dim), nn.Sigmoid() ) def forward(self, x): encoder_out = self.encoder(x) decoder_out = self.decoder(encoder_out) return encoder_out, decoder_out
5 超参数定义
batch_size = 100 num_epochs = 50 in_dim = 784 hidden_size = 30 expect_tho = 0.05
6 训练
train_loader, test_loader = get_mnist_loader(batch_size=batch_size, shuffle=True) autoEncoder = AutoEncoder(in_dim=in_dim, hidden_size=hidden_size, out_dim=in_dim) if torch.cuda.is_available(): autoEncoder.cuda() # 注:将模型放到GPU上,因此后续传入的数据必须也在GPU上 Loss = nn.BCELoss() Optimizer = optim.Adam(autoEncoder.parameters(), lr=0.001) # 定义期望平均激活值和KL散度的权重 tho_tensor = torch.FloatTensor([expect_tho for _ in range(hidden_size)]) if torch.cuda.is_available(): tho_tensor = tho_tensor.cuda() _beta = 3 # def kl_1(p, q): # p = torch.nn.functional.softmax(p, dim=-1) # _kl = torch.sum(p*(torch.log_softmax(p,dim=-1)) - torch.nn.functional.log_softmax(q, dim=-1),1) # return torch.mean(_kl) for epoch in range(num_epochs): time_epoch_start = time.time() for batch_index, (train_data, train_label) in enumerate(train_loader): if torch.cuda.is_available(): train_data = train_data.cuda() train_label = train_label.cuda() input_data = train_data.view(train_data.size(0), -1) encoder_out, decoder_out = autoEncoder(input_data) loss = Loss(decoder_out, input_data) # 计算并增加KL散度到loss _kl = KL_devergence(tho_tensor, encoder_out) loss += _beta * _kl Optimizer.zero_grad() loss.backward() Optimizer.step() print('Epoch: {}, Loss: {:.4f}, Time: {:.2f}'.format(epoch + 1, loss, time.time() - time_epoch_start))
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