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CS231n学习笔记--13. Generative Models

1. Unsupervised Learning

Supervised vs Unsupervised Learning:

2. Generative Models

概述:

Generative Models的作用:

Generative Models的分类:

3. PixelRNN and PixelCNN

基本原理:

PixelRNN:

PixelCNN:

Training is faster than PixelRNN (can parallelize convolutions since context region values known from training images)
Generation must still proceed sequentially=> still slow

Generation Samples:

PixelRNN and PixelCNN

4. Variational Autoencoders (VAE)

4.1 与PixelRNN/PixelCNN的比较:

4.2 Some background first: Autoencoders:

Tips:

如果将其用于特征提取,则在训练之后,将decoder部分丢弃!

Autoencoders can reconstruct data, and can learn features to initialize a supervised model!

4.3 Variational Autoencoders

利用高斯分布随机生成特征Z:

Variational Autoencoders: Intractability

$$pθ(z)$$ 跟据高斯分布随机获得, $$pθ(x|z)$$ 根据decoder net获得,而为每个z计算 $$pθ(x|z)$$ 并最终积分得到 $$pθ(x)$$ 是不可能的!

解决办法:

如何进行优化:

4.4 Generating Data

4.5 性能分析:

5. Generative Adversarial Networks (GAN)

回顾:

5.1 Training GANs: Two-player game

Generator network: try to fool the discriminator by generating real-looking images
Discriminator network: try to distinguish between real and fake images

网络优化:

优化存在的问题:

解决办法:

GAN training algorithm:

5.2 Generative Adversarial Nets

Generated samples:

Generative Adversarial Nets: Convolutional Architectures

Generator is an upsampling network with fractionally-strided convolutions
Discriminator is a convolutional network

Generator网络结构:

Samples from the model look amazing!

Generative Adversarial Nets: Interpretable Vector Math

GANs的优缺点:

6. 回顾:

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