NLP DLforDS
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This is the presentation for NLP 2018 Spring class, talked about the Deep learning application for dialogue systems
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NLP DLforDS
- 1. Deep Learning for Dialogue Systems Liangqun Lu PhD program in Biology/Bioinformatics MS program in Computer Science
- 2. JARVIS (Just Another Rather Very Intelligent System) "J.A.R.V.I.S., are you up?" "For you sir, always." "J.A.R.V.I.S.? You ever hear the tale of Jonah?" "I wouldn't consider him a role model." "J.A.R.V.I.S., where's my flight power?!" "Working on it, sir. This is a prototype." https://www.youtube.com/watch?v=ZwOxM0-byvc
- 4. Intelligent Sentence Generation for Dialogues DeepLearningtoolbox 1. Seq2Seq Generation -- LSTM -- RNN 2. RL for Generation --- Reinforcement Learning (RL) 3. SeqGAN for Generation --- Generative Adversarial Nets (GANs)
- 5. 1. Seq2Seq Generation Source: cs224u-2016-li-chatbots Encoder Decoder GeneratorInput Maximum Likelihood Estimation: Mutual Information:
- 6. RNN (Recurrent Neural Network)
- 7. Long short term memories (LSTMs)
- 9. Seq2Seq encoder- decoder example in keras Encoder Model Decoder Model
- 10. Summaries Seq2seq model can generate output sentences based on the input sentences The maximum likelihood estimation (MLE) objective function does not guarantee good responses to human beings in read world. It is likely to generate highly dull and generic responses such as I dont know regardless of the input, which is a buzzkiller in a conversation. Mutual Information (MI) could avoid ~30% dull responses. It is likely to get stuck in an infinite loop of repetitive responses.
- 11. 2. RL for sentence generation Encoder Decoder Generator (x) Input (h) Human R(h, x)
- 12. Hung-yi Lee : RL and GAN for Sentence Generation and Chat-bot
- 13. Hung-yi Lee : RL and GAN for Sentence Generation and Chat-bot
- 14. Hung-yi Lee : RL and GAN for Sentence Generation and Chat-bot
- 15. RL implemented in dialogue systems
- 16. Evaluation Training: OpenSubtitles dataset (0.8 M pairs) Testing: 1000 input messages Length of dialogue; lexical diversity; human evaluation
- 17. Summaries Reinforcement Learning implemented in dialogue generation rewards the conversation with properties: informativity, coherence and ease of answering The model has the advantages on diversity, length, better human judges and more interactive responses This approach makes it potential to generate long-term dialogues
- 18. 3. SeqGAN for sentence generation
- 20. SeqGAN for sentence generation Encoder Decoder Discriminator (x) Input Scalar
- 23. Random: random token generation MLE: Seq2Seq with MLE objective function SS: scheduled sampling PG-BLEU: policy gradient with BLEU * bilingual evaluation understudy * NLL oracle:
- 24. The stability of SeqGAN depends on the training strategy such as g-steps, d-steps and epoch number k for g-step g-steps=1, d-steps=5, k=3 has the best performance
- 25. Table 2: 16,394 Chinese quatrains Table 3: 11,092 paragraphs Table 4: 695 music
- 26. Summaries Generative Adversarial Net (GAN) that uses a discriminative model to guide the training of the generative model has enjoyed considerable success in generating real-valued data. SeqGAN applying policy gradient to update from the discriminative model to the generative model demonstrates significant improvements in synthetic and real-world data.
- 27. References 1. Li, Jiwei, et al. "Deep reinforcement learning for dialogue generation." arXiv preprint arXiv:1606.01541 (2016) 2. Yu, Lantao, et al. "SeqGAN: Sequence Generative Adversarial Nets with Policy Gradient" (2016) 3. Stanford CS224d: Deep Learning for Natural Language Processing 4. DL/ML Tutorial from Hung-yi Lee
Editor's Notes
- #3: My interest on this topic is actually from Iron Man movies. In the movies, we know that Iron man tony stark has an intelligent assistant called JARVIS, they have many interesting conversations. It will be a pleasure to have such smart virtual friend.
- #4: Deep Learning techniques have successful applications in many areas, including Natural Language Processing. These two papers from 2 years played an important role in dialogue systems, with advanced skills in RL and GAN.
- #5: In my understanding, deep learning toolbox provides tools which can be applied in dialogues, at least in these 3 steps. So far, there are some intelligent sentence generation for dialogues from these techniques.
- #6: In seq2seq generation, the simplified architecture is like this one. Here is an example: There are 2 optimizations in this system, MLE and MI.
- #7: The seq2seq model is based on RNN with LSTM. RNN is ---, the structure is this, including input and output. Unfold shows the details here, from xt to ot, the input actually is xt, s(t-1) and the output is ot and st, s(t-1) records the previous information, which is important in sequence tasks. The advantage of RNN, compared to other DL models, is that RNN is suitable to process sequence data.
- #8: However RNN has gradient exploding or vanishing problem when the sequence is long, because the optimization has to consider all memory from previous steps. LSTM was developed to optimize the memory problem with three gates in a cell.
- #9: Encoder and Decoder, a function used to model the complex system.
- #10: An encoder and decoder example from Keras shows the parameters in layers. The encoder and decoder has the same number 256.
- #20: Evaluating dialogue systems is difficult. Metrics such as BLEU (Papineni et al., 2002) and perplexity have been widely used for dialogue quality evaluation (Li et al., 2016a; Vinyals and Le, 2015; Sordoni et al., 2015), but it is widely debated how well these automatic metrics are correlated with true response quality (Liu et al., 2016; Galley et al., 2015). Since the goal of the proposed system is not to predict the highest probability response, but rather the long-term success of the dialogue, we do not employ BLEU or perplexity for evaluation.
- #21: We propose to measure the ease of answering a generated turn by using the negative log likelihood of responding to that utterance with a dull response.
- #36: Li, Jiwei, et al. "Deep reinforcement learning for dialogue generation." arXiv preprint arXiv:1606.01541 (2016). Yu, Lantao, et al. "SeqGAN: Sequence Generative Adversarial Nets with Policy Gradient" (2016)