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Sequence Models Explained
- 2. 2 Roozbeh Sanaei https://towardsdatascience.com/an-overview-for-text-representations-in-nlp-311253730af1 One-Hot Word Representations
- 3. 3 Roozbeh Sanaei https://en.wikipedia.org/wiki/File:Recurrent_neural_network_unfold.svg Recurrent Neural Networks
- 5. 5 Roozbeh Sanaei https://stanford.edu/~shervine/teaching/cs-230/cheatsheet-recurrent-neural-networks Different types of RNNs One to One One to Many Many to One Many to Many (Same size) Many to Many (Different size)
- 6. 6 Roozbeh Sanaei https://lorenlugosch.github.io/posts/2019/02/seq2seq/ Sequence models as Markov Decision Processes 𝑝𝜃 𝒚 𝒙 = 𝑝𝜃 𝑦1, 𝑦2, 𝑦3, … , 𝑦𝑁 𝒙 = 𝑛=1 𝑁 𝑝𝜃 𝑦𝑛 𝑦𝑛−1, 𝑦𝑛−2, … , 𝒙
- 7. 7 Roozbeh Sanaei http://www.sunlab.org/teaching/cse6250/fall2222/lab/dl-rnn/ Vanishing vs exploding gradient problem
- 8. 8 Roozbeh Sanaei https://towardsdatascience.com/understanding-gru-networks-2ef37df6c9be Idea behind GRU and LSTM • The cell state is kind of like a conveyor belt. • It runs straight down the entire chain, with only some minor linear interactions. It’s very easy for information to just flow along it unchanged. • Gates are a way to optionally let information through.
- 9. 9 Roozbeh Sanaei http://colah.github.io/posts/2015-08-Understanding-LSTMs/ LSTM Forget gate: Decide which information to throw away from the cell state. Input gate: Decide which information to store to the cell state Update: Update the cell state scaled by input and forget gates. Output: Output based on the updated cell state.
- 10. 10 Roozbeh Sanaei https://towardsdatascience.com/understanding-gru-networks-2ef37df6c9be GRU Update gate Reset gate New info The update gate decides how much of the past information needs to be passed along to the future. The reset gate is used from the model to decide how much of the past information to forget
- 11. 11 Roozbeh Sanaei Bidirectional RNN • Independent RNNs • Outputs of are concatenated at each time step • Allows the networks to have both backward and forward information https://towardsdatascience.com/understanding-bidirectional- rnn-in-pytorch-5bd25a5dd66
- 13. 13 Roozbeh Sanaei Featurized Word Representations https://dzone.com/articles/introduction-to-word-vectors
- 14. 14 Roozbeh Sanaei Properties of word embeddings https://towardsdatascience.com/word-embeddings-for-nlp-5b72991e01d4
- 15. 15 Roozbeh Sanaei Embedding Matrix https://neuro.cs.ut.ee/the-use-of-embeddings-in-openai-five/ embedding Matrix Word embedding Word Representations can be learned from large corpuses and be used (or fine-tuned) on new tasks
- 16. 16 Roozbeh Sanaei Neural Language Model https://x-wei.github.io/notes/xcs224n-lecture6.html
- 19. 19 Roozbeh Sanaei GloVe: Global Vectors for Word Representations http://building-babylon.net/tag/glove/
- 20. 20 Roozbeh Sanaei Greedy Search vs Beam Search 𝐿𝑒𝑛𝑔𝑡ℎ 𝑁𝑜𝑟𝑚𝑎𝑙𝑖𝑧𝑎𝑡𝑖𝑜𝑛 = 1 𝐿∝
- 21. 21 Roozbeh Sanaei Beam Search Failure Analysis Ground Truth sentence likelihood turns out to be higher → 𝐵𝑒𝑎𝑚 𝑆𝑒𝑎𝑟𝑐ℎ 𝑖𝑠 𝑎𝑡 𝐹𝑎𝑢𝑙𝑡 Ground Truth sentence likelihood turns out to be lower → 𝑅𝑁𝑁 𝑀𝑜𝑑𝑒𝑙 𝑖𝑠 𝑎𝑡 𝐹𝑎𝑢𝑙𝑡
- 22. 22 Roozbeh Sanaei Bleu Score R1: but thou shalt love thy neighbor as thyself R2: but have love for your neighbor as for yourself R3: but love your neighbors as you love yourself D: but love other love friend for love yourself D(but)=1 D(love)=3 D(other)=1 D(friend)=1 D(for)=1 D(yourself)=1 R(but)=1 R(love)=2 [appears twice in R3] R(other)=0 R(friend)=0 R(for)=2 [appears twice in R2] R(yourself)=1 MIN(D(but), R(but))=MIN(1, 1)=1 MIN(D(love), R(love))=MIN(3, 2)=2 MIN(D(other), R(other))=MIN(1, 0)=0 MIN(D(friend), R(friend))=MIN(1,0)=0 MIN(D(for), R(for))=MIN(1, 2)=1 MIN(D(yourself), R(yourself))=MIN(1,1)=1 Total= 5 Total = 5 Bleu Score = 5/8 https://towardsdatascience.com/nlp-metrics-made-simple-the- bleu-score-b06b14fbdbc1
- 27. 27 Roozbeh Sanaei Attention benefits https://web.stanford.edu/class/cs224n/slides/cs224n-2019-lecture14-transformers.pdf • Constant ‘path length’ between any two positions. • Unbounded memory. • Trivial to parallelize (per layer). • Models Self-Similarity. • Relative attention provides expressive timing, equivariance, and extends naturally to graphs.
- 28. 28 Roozbeh Sanaei Transformer https://towardsai.net/p/nlp/getting-meaning-from-text-self- attention-step-by-step-video • Transforms one sequence into another one word at a time based on previous elements. • During the training stage, each word is predicted based on words before that in the sentence according to Ground truth • During the test stage, each word is predicted based on the predicted words before that