基于pytorch写一个gan的损失函数
时间: 2023-07-25 13:39:37 浏览: 58
下面是一个基于PyTorch实现的GAN损失函数的示例代码:
```python
import torch.nn.functional as F
def gan_loss_function(real_output, fake_output):
# 计算生成器损失
gen_loss = F.binary_cross_entropy_with_logits(fake_output, torch.ones_like(fake_output))
# 计算判别器损失
real_loss = F.binary_cross_entropy_with_logits(real_output, torch.ones_like(real_output))
fake_loss = F.binary_cross_entropy_with_logits(fake_output, torch.zeros_like(fake_output))
disc_loss = real_loss + fake_loss
return gen_loss, disc_loss
```
其中,`real_output`是判别器对真实样本的输出,`fake_output`是判别器对生成样本的输出。`binary_cross_entropy_with_logits`函数是PyTorch中用于计算二元交叉熵损失的函数,可以方便地计算生成器损失和判别器损失。最终返回的是生成器损失和判别器损失。
相关问题
用pytorch写一个GAN代码
这里提供一个简单的GAN代码,使用PyTorch实现:```python
import torch
import torch.nn as nn
import torch.optim as optim
import torchvision.datasets as dset
import torchvision.transforms as transforms
from torch.utils.data import DataLoader
from torchvision.utils import save_image# 定义生成器
class Generator(nn.Module):
def __init__(self, input_size, hidden_size, output_size):
super(Generator, self).__init__()
self.fc1 = nn.Linear(input_size, hidden_size)
self.fc2 = nn.Linear(hidden_size, hidden_size)
self.fc3 = nn.Linear(hidden_size, output_size)
self.relu = nn.ReLU()
self.tanh = nn.Tanh() def forward(self, x):
x = self.relu(self.fc1(x))
x = self.relu(self.fc2(x))
x = self.tanh(self.fc3(x))
return x# 定义判别器
class Discriminator(nn.Module):
def __init__(self, input_size, hidden_size, output_size):
super(Discriminator, self).__init__()
self.fc1 = nn.Linear(input_size, hidden_size)
self.fc2 = nn.Linear(hidden_size, hidden_size)
self.fc3 = nn.Linear(hidden_size, output_size)
self.relu = nn.ReLU()
self.sigmoid = nn.Sigmoid() def forward(self, x):
x = self.relu(self.fc1(x))
x = self.relu(self.fc2(x))
x = self.sigmoid(self.fc3(x))
return x# 定义超参数
batch_size = 100
input_size = 100
hidden_size = 256
output_size = 784
num_epochs = 200# 加载MNIST数据集
transform = transforms.Compose([
transforms.ToTensor(),
transforms.Normalize(mean=(.5,), std=(.5,))
])
train_dataset = dset.MNIST(root='./data', train=True, transform=transform, download=True)
train_loader = DataLoader(train_dataset, batch_size=batch_size, shuffle=True)# 初始化生成器和判别器
G = Generator(input_size, hidden_size, output_size)
D = Discriminator(output_size, hidden_size, 1)# 定义损失函数和优化器
criterion = nn.BCELoss()
G_optimizer = optim.Adam(G.parameters(), lr=.0002)
D_optimizer = optim.Adam(D.parameters(), lr=.0002)# 训练GAN模型
for epoch in range(num_epochs):
for i, (images, _) in enumerate(train_loader):
# 训练判别器
real_labels = torch.ones(batch_size, 1)
fake_labels = torch.zeros(batch_size, 1)
real_images = images.view(batch_size, -1)
z = torch.randn(batch_size, input_size)
fake_images = G(z) D_real_loss = criterion(D(real_images), real_labels)
D_fake_loss = criterion(D(fake_images), fake_labels)
D_loss = D_real_loss + D_fake_loss
D_optimizer.zero_grad()
D_loss.backward()
D_optimizer.step() # 训练生成器
z = torch.randn(batch_size, input_size)
fake_images = G(z)
G_loss = criterion(D(fake_images), real_labels)
G_optimizer.zero_grad()
G_loss.backward()
G_optimizer.step() # 打印损失值
if (i+1) % 100 == :
print('Epoch [{}/{}], Step [{}/{}], D_loss: {:.4f}, G_loss: {:.4f}'
.format(epoch+1, num_epochs, i+1, len(train_loader), D_loss.item(), G_loss.item())) # 保存生成的图像
if (epoch+1) % 10 == :
fake_images = fake_images.view(batch_size, 1, 28, 28)
save_image(fake_images, './samples/sample_{}.png'.format(epoch+1))
```这个代码实现了一个简单的GAN模型,用于生成手写数字图像。其中,生成器和判别器都是简单的全连接神经网络,损失函数采用二元交叉熵,优化器采用Adam算法。在训练过程中,每隔一定的步数就会打印出当前的损失值,并保存生成的图像。
基于pytorch,编一个GAN的代码
好的,以下是一个简单的GAN代码,用于生成手写数字图像:
```
import torch
import torch.nn as nn
import torch.optim as optim
import torchvision.datasets as dset
import torchvision.transforms as transforms
import torchvision.utils as vutils
from torch.utils.data import DataLoader
# 定义生成器和判别器
class Generator(nn.Module):
def __init__(self, ngf=64):
super(Generator, self).__init__()
self.main = nn.Sequential(
nn.ConvTranspose2d(100, ngf*8, 4, 1, 0, bias=False),
nn.BatchNorm2d(ngf*8),
nn.ReLU(True),
nn.ConvTranspose2d(ngf*8, ngf*4, 4, 2, 1, bias=False),
nn.BatchNorm2d(ngf*4),
nn.ReLU(True),
nn.ConvTranspose2d(ngf*4, ngf*2, 4, 2, 1, bias=False),
nn.BatchNorm2d(ngf*2),
nn.ReLU(True),
nn.ConvTranspose2d(ngf*2, ngf, 4, 2, 1, bias=False),
nn.BatchNorm2d(ngf),
nn.ReLU(True),
nn.ConvTranspose2d(ngf, 1, 4, 2, 1, bias=False),
nn.Tanh()
)
def forward(self, input):
return self.main(input)
class Discriminator(nn.Module):
def __init__(self, ndf=64):
super(Discriminator, self).__init__()
self.main = nn.Sequential(
nn.Conv2d(1, ndf, 4, 2, 1, bias=False),
nn.LeakyReLU(0.2, inplace=True),
nn.Conv2d(ndf, ndf*2, 4, 2, 1, bias=False),
nn.BatchNorm2d(ndf*2),
nn.LeakyReLU(0.2, inplace=True),
nn.Conv2d(ndf*2, ndf*4, 4, 2, 1, bias=False),
nn.BatchNorm2d(ndf*4),
nn.LeakyReLU(0.2, inplace=True),
nn.Conv2d(ndf*4, ndf*8, 4, 2, 1, bias=False),
nn.BatchNorm2d(ndf*8),
nn.LeakyReLU(0.2, inplace=True),
nn.Conv2d(ndf*8, 1, 4, 1, 0, bias=False),
nn.Sigmoid()
)
def forward(self, input):
return self.main(input).view(-1, 1)
# 定义训练函数
def train(netG, netD, dataloader, device, epochs=5, lr=0.0002, beta1=0.5):
criterion = nn.BCELoss()
optimizerG = optim.Adam(netG.parameters(), lr=lr, betas=(beta1, 0.999))
optimizerD = optim.Adam(netD.parameters(), lr=lr, betas=(beta1, 0.999))
fixed_noise = torch.randn(64, 100, 1, 1, device=device)
for epoch in range(epochs):
for i, data in enumerate(dataloader, 0):
netD.zero_grad()
real_cpu = data[0].to(device)
b_size = real_cpu.size(0)
label = torch.full((b_size,), 1, device=device)
output = netD(real_cpu)
errD_real = criterion(output, label)
errD_real.backward()
D_x = output.mean().item()
noise = torch.randn(b_size, 100, 1, 1, device=device)
fake = netG(noise)
label.fill_(0)
output = netD(fake.detach())
errD_fake = criterion(output, label)
errD_fake.backward()
D_G_z1 = output.mean().item()
errD = errD_real + errD_fake
optimizerD.step()
netG.zero_grad()
label.fill_(1)
output = netD(fake)
errG = criterion(output, label)
errG.backward()
D_G_z2 = output.mean().item()
optimizerG.step()
print('[%d/%d][%d/%d] Loss_D: %.4f Loss_G: %.4f D(x): %.4f D(G(z)): %.4f / %.4f'
% (epoch+1, epochs, i+1, len(dataloader), errD.item(), errG.item(), D_x, D_G_z1, D_G_z2))
vutils.save_image(real_cpu, '%s/real_samples.png' % "./results", normalize=True)
fake = netG(fixed_noise)
vutils.save_image(fake.detach(), '%s/fake_samples_epoch_%03d.png' % ("./results", epoch+1), normalize=True)
# 加载数据集
transform = transforms.Compose([
transforms.ToTensor(),
transforms.Normalize((0.5,), (0.5,))
])
dataset = dset.MNIST(root="./data", download=True, transform=transform)
dataloader = DataLoader(dataset, batch_size=128, shuffle=True, num_workers=2)
# 训练
device = torch.device("cuda:0" if (torch.cuda.is_available()) else "cpu")
netG = Generator().to(device)
netD = Discriminator().to(device)
train(netG, netD, dataloader, device)
```
这是一个生成手写数字图像的GAN,使用的数据集是MNIST。在训练过程中,生成器和判别器通过对抗的方式互相提升,最终生成器可以生成逼真的手写数字图像。