小编给大家分享一下pytorch:怎么实现简单的GAN，相信大部分人都还不怎么了解，因此分享这篇文章给大家参考一下，希望大家阅读完这篇文章后大有收获，下面让我们一起去了解一下吧！
代码如下
# -*- coding: utf-8 -*-
"""
Created on Sat Oct 13 10:22:45 2018
"""
import torch
from torch import nn
from torch.autograd import Variable
import torchvision.transforms as tfs
from torch.utils.data import DataLoader, sampler
from torchvision.datasets import MNIST
import numpy as np
import matplotlib.pyplot as plt
import matplotlib.gridspec as gridspec
plt.rcParams['figure.figsize'] = (10.0, 8.0) # 设置画图的尺寸
plt.rcParams['image.interpolation'] = 'nearest'
plt.rcParams['image.cmap'] = 'gray'
def show_images(images): # 定义画图工具
images = np.reshape(images, [images.shape[0], -1])
sqrtn = int(np.ceil(np.sqrt(images.shape[0])))
sqrtimg = int(np.ceil(np.sqrt(images.shape[1])))
fig = plt.figure(figsize=(sqrtn, sqrtn))
gs = gridspec.GridSpec(sqrtn, sqrtn)
gs.update(wspace=0.05, hspace=0.05)
for i, img in enumerate(images):
ax = plt.subplot(gs[i])
plt.axis('off')
ax.set_xticklabels([])
ax.set_yticklabels([])
ax.set_aspect('equal')
plt.imshow(img.reshape([sqrtimg,sqrtimg]))
return
def preprocess_img(x):
x = tfs.ToTensor()(x)
return (x - 0.5) / 0.5
def deprocess_img(x):
return (x + 1.0) / 2.0
class ChunkSampler(sampler.Sampler): # 定义一个取样的函数
"""Samples elements sequentially from some offset.
Arguments:
num_samples: # of desired datapoints
start: offset where we should start selecting from
"""
def __init__(self, num_samples, start=0):
self.num_samples = num_samples
self.start = start
def __iter__(self):
return iter(range(self.start, self.start + self.num_samples))
def __len__(self):
return self.num_samples
NUM_TRAIN = 50000
NUM_VAL = 5000
NOISE_DIM = 96
batch_size = 128
train_set = MNIST('E:/data', train=True, transform=preprocess_img)
train_data = DataLoader(train_set, batch_size=batch_size, sampler=ChunkSampler(NUM_TRAIN, 0))
val_set = MNIST('E:/data', train=True, transform=preprocess_img)
val_data = DataLoader(val_set, batch_size=batch_size, sampler=ChunkSampler(NUM_VAL, NUM_TRAIN))
imgs = deprocess_img(train_data.__iter__().next()[0].view(batch_size, 784)).numpy().squeeze() # 可视化图片效果
show_images(imgs)
#判别网络
def discriminator():
net = nn.Sequential(
nn.Linear(784, 256),
nn.LeakyReLU(0.2),
nn.Linear(256, 256),
nn.LeakyReLU(0.2),
nn.Linear(256, 1)
)
return net
#生成网络
def generator(noise_dim=NOISE_DIM):
net = nn.Sequential(
nn.Linear(noise_dim, 1024),
nn.ReLU(True),
nn.Linear(1024, 1024),
nn.ReLU(True),
nn.Linear(1024, 784),
nn.Tanh()
)
return net
#判别器的 loss 就是将真实数据的得分判断为 1，假的数据的得分判断为 0，而生成器的 loss 就是将假的数据判断为 1
bce_loss = nn.BCEWithLogitsLoss()#交叉熵损失函数
def discriminator_loss(logits_real, logits_fake): # 判别器的 loss
size = logits_real.shape[0]
true_labels = Variable(torch.ones(size, 1)).float()
false_labels = Variable(torch.zeros(size, 1)).float()
loss = bce_loss(logits_real, true_labels) + bce_loss(logits_fake, false_labels)
return loss
def generator_loss(logits_fake): # 生成器的 loss
size = logits_fake.shape[0]
true_labels = Variable(torch.ones(size, 1)).float()
loss = bce_loss(logits_fake, true_labels)
return loss
# 使用 adam 来进行训练，学习率是 3e-4, beta1 是 0.5, beta2 是 0.999
def get_optimizer(net):
optimizer = torch.optim.Adam(net.parameters(), lr=3e-4, betas=(0.5, 0.999))
return optimizer
def train_a_gan(D_net, G_net, D_optimizer, G_optimizer, discriminator_loss, generator_loss, show_every=250,
noise_size=96, num_epochs=10):
iter_count = 0
for epoch in range(num_epochs):
for x, _ in train_data:
bs = x.shape[0]
# 判别网络
real_data = Variable(x).view(bs, -1) # 真实数据
logits_real = D_net(real_data) # 判别网络得分
sample_noise = (torch.rand(bs, noise_size) - 0.5) / 0.5 # -1 ~ 1 的均匀分布
g_fake_seed = Variable(sample_noise)
fake_images = G_net(g_fake_seed) # 生成的假的数据
logits_fake = D_net(fake_images) # 判别网络得分
d_total_error = discriminator_loss(logits_real, logits_fake) # 判别器的 loss
D_optimizer.zero_grad()
d_total_error.backward()
D_optimizer.step() # 优化判别网络
# 生成网络
g_fake_seed = Variable(sample_noise)
fake_images = G_net(g_fake_seed) # 生成的假的数据
gen_logits_fake = D_net(fake_images)
g_error = generator_loss(gen_logits_fake) # 生成网络的 loss
G_optimizer.zero_grad()
g_error.backward()
G_optimizer.step() # 优化生成网络
if (iter_count % show_every == 0):
print('Iter: {}, D: {:.4}, G:{:.4}'.format(iter_count, d_total_error.item(), g_error.item()))
imgs_numpy = deprocess_img(fake_images.data.cpu().numpy())
show_images(imgs_numpy[0:16])
plt.show()
print()
iter_count += 1
D = discriminator()
G = generator()
D_optim = get_optimizer(D)
G_optim = get_optimizer(G)
train_a_gan(D, G, D_optim, G_optim, discriminator_loss, generator_loss)以上是“pytorch:怎么实现简单的GAN”这篇文章的所有内容，感谢各位的阅读！相信大家都有了一定的了解，希望分享的内容对大家有所帮助，如果还想学习更多知识，欢迎关注创新互联行业资讯频道！
