1. Self-training with Products of Latent Variable Grammars Zhongqiang Huang, Mary Harper, and Slav Petrov

2. Overview  Motivation and Prior Related Research  Experimental Setup  Results  Analysis  Conclusions 2

3. Parse Tree Sentence Parameters... Derivations PCFG-LA Parser [Matsuzaki et. al ’05] [Petrov et. al ’06] [Petrov & Klein’07] 3

4. PCFG-LA Parser NP NP1NP2  Hierarchical splitting (& merging) NP1NP2NP3NP4 NP1NP2NP3NP4NP5NP6NP7NP8 Split to 2 Split to 4 Split to 8 Original Node … Increased Model Complexity n-th grammar: grammar trained after n-th split-merge rounds …  Typical learning curve  Grammar Order Selection  Use development set

5. PCFG-LA Properties Hierarchical Training ◦ Increase the number of latent states hierarchically Adaptive State Splitting ◦ Goal is to split complex categories more and simple categories less ◦ Idea: split everything, and then roll back the splits that are least useful (use loss in likelihood from removing splits, typically 50% are undone) Parameter Smoothing (Pool statistics) Decoding Methods (Max Rule Product) Coarse-to-Fine Parsing (To speed up decoding)

6. Max-Rule Decoding (Single Grammar) S NP VP [Goodman ’98, Matsuzaki et al. ’05, Petrov & Klein ’07] 6

7. Variability 7 [Petrov, ’10]

8. ... Max-Rule Decoding (Multiple Grammars) [Petrov, ’10] Treebank 8

9. Product Model Results 9 [Petrov, ’10]

10. Motivation for Self-Training 10

11. Self-training (ST) Hand Labeled Unlabeled Data Train Label Automatically Labeled Data Train Select with dev 11

12. Self-training (ST) Hand Labeled Train Model Label New Model Train Automatically Labeled Data Unlabeled Labeled 12

13. Self-Training Curve 13

14. WSJ Self-Training Results F score 14 [Huang & Harper, ’09]

15. Self-Trained Grammar Variability Self-trained Parser 15

16. Self-Trained Grammar Variability Self-trained Round 7 Self-trained Round 6 16

17. Summary  Two issues: Variability & Over-fitting  Product model  Makes use of variability  Over-fitting remains in individual grammars  Self-training  Alleviates over-fitting  Variability remains in individual grammars  Next step: combine self-training with product models 17

18. Experimental Setup  Two genres:  WSJ: Sections 2-21 for training, 22 for dev, 23 for test, 176.9K sentences per self-trained grammar  Broadcast News: WSJ+80% of BN for training, 10% for dev, 10% for test (see paper),  Training Scenarios: train 10 models with different seeds and combine using Max-Rule Decoding  Regular: treebank training with up to 7 split-merge iterations  Self-Training: three methods with up to 7 split-merge iterations 18

19. ST-Reg Label Automatically Labeled Data Unlabeled Data Hand Labeled Train Multiple Grammars? Product Train Select with dev set 19 Single automatically labeled set by round 6 product

20. ST-Prod Label Automatically Labeled Data Unlabeled Data Hand Labeled Train Product Train Use more data? Product 20 Single automatically labeled set by round 6 product

21. ST-Prod-Mult Hand Labeled Train Label Product Label Product 21 10 different automatically labeled sets by round 6 product

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25. A Closer Look at Regular Results 25

26. A Closer Look at Regular Results 26

27. A Closer Look at Regular Results 27

28. A Closer Look at Self-Training Results 28

29. A Closer Look at Self-Training Results 29

30. A Closer Look at Self-Training Results 30

31. Analysis of Rule Variance  We measure the average empirical variance of the log posterior probabilities of the rules among the learned grammars over a held-out set S to get at the diversity among the grammars: 31

32. Analysis of Rule Variance 32

33. English Test Set Results (WSJ 23) Single ParserRerankerProductParser Combination [Charniak ’00]Petrov et al. ’06][Carreras et al. ’08][Huang & Harper ’08]This Work[Petrov ’10]This Work[Charniak & Johnson ’05][Huang ’08][McClosky et al. ’06][Sagae & Lavie ’06][Fossum & Knight ’09][Zhang et al. ’09] 33

34. Broadcast News 34

35. Conclusions  Very high parse accuracies can be achieved by combining self-training and product models on newswire and broadcast news parsing tasks.  Two important factors: 1. Accuracy of the model used to parse the unlabeled data 2. Diversity of the individual grammars 35