Neural Nets for NLP - Latent Random Variables

Neural Nets for NLP - Latent Random Variables

Graham Neubig via YouTube Direct link

Intro

1 of 25

1 of 25

Intro

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Neural Nets for NLP - Latent Random Variables

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  1. 1 Intro
  2. 2 Discriminative vs. Generative Models • Discriminative model: calculate the probability of output given
  3. 3 Quiz: What Types of Variables? • In the an attentional sequence-to-sequence model using MLE/teacher forcing, are the following variables observed or latent? deterministic or random?
  4. 4 Why Latent Random Variable
  5. 5 What is Latent Random Variable Model
  6. 6 A Latent Variable Model
  7. 7 An Example (Goersch 2016)
  8. 8 Variational Inference
  9. 9 Practice
  10. 10 Variational Autoencoders
  11. 11 VAE vs. AE
  12. 12 Problem! Sampling Breaks Backprop
  13. 13 Solution: Re-parameterization Trick
  14. 14 Motivation for Latent Variables • Allows for a consistent latent space of sentences?
  15. 15 Difficulties in Training
  16. 16 KL Divergence Annealing • Basic idea: Multiply KL term by a constant starting at zero, then gradually increase to 1 • Result: model can learn to use z before getting penalized
  17. 17 Solution 2: Weaken the Decoder . But theoretically still problematic: it can be shown that the optimal strategy is to ignore z when it is not necessary (Chen et al. 2017)
  18. 18 Aggressive Inference Network Learning
  19. 19 Discrete Latent Variables?
  20. 20 Enumeration
  21. 21 Method 2: Sampling • Randomly sample a subset of configurations of z and optimize with respect to this subset
  22. 22 Method 3: Reparameterization (Maddison et al. 2017, Jang et al. 2017)
  23. 23 Variational Models of Language Processing (Miao et al. 2016) • Present models with random variables for document modeling and question answer pair selection
  24. 24 Controllable Text Generation (Hu et al. 2017)
  25. 25 Symbol Sequence Latent Variables (Miao and Blunsom 2016) • Encoder-decoder with a sequence of latent symbols

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