Assignment №4 Named entity recognition (NER).

CSCI544: Homework Assignment №4
Introduction
This assignment gives you hands-on experience in building deep learning
models on named entity recognition (NER).
Here is a table of models that will be covered in this assignment
Model Expected F1 dev
BiLSTM 77
BiLSTM with Glove 88
Transformer Encoder 61
Table 1: Models
Dataset
We will use the CoNLL-2003 corpus to build a neural network for NER. link:
https://huggingface.co/datasets/conll2003 It is convenient to use
the datasets library to get this dataset
1 import datasets
2
3 dataset = datasets.load_dataset("conll2003")
Use the convenient .map() function to prepossess your dataset seamlessly.
It can be used to add keys, update keys
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Example:
1 def convert_word_to_id(sample):
2 # Code to convert all tokens to their respective indexes
3 return {
4 'input_ids': [
5 word2idx[token]
6 for token in sample['tokens']
7 ]
8 }
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10 dataset.map(convert_word_to_id)
We added the input ids column to this dataset.
Since we do not permit you to use ’pos tags’, ’chunk tags’, remove the following columns from the dataset: [’pos tags’, ’chunk tags’]
Rename the ner tags to labels
The string values of NER tags are https://huggingface.co/datasets/
conll2003#:~:text=%3A%2022%7D-,ner_tags,-%3A%20a%20list%20of
Glove Embeddings
We provide you with a file named glove.6B.100d.gz, which is the GloVe
word embeddings [1]. Alternatively, you can download it from https://
nlp.stanford.edu/data/glove.6B.zip
Download script for ipynb files:
1 !wget http://nlp.stanford.edu/data/glove.6B.zip
2 !unzip glove.6B.zip
Evaluation
We will also provide you with an evaluation function ’evaluate’ from: https:
//github.com/sighsmile/conlleval Whenever we ask you for accuracy, precision, recall, or f1 score, we are referring you to use this
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script. If this script is not used, that will lead to a penalty
Download script for ipynb
1 !wget https://raw.githubusercontent.com/sighsmile/conlleval/master/conlleval.py
Usage:
1 # This is an example and the code will fail
2 # Because the preds is not the required length
3 from conlleval import evaluate
4 import itertools
5
6 # labels = ner_tags
7 # Map the labels back to their corresponding tag strings
8 labels = [
9 list(map(idx2tag.get, labels))
10 for labels in dataset['validation']['labels']
11 ]
12 # This is the prediction by your model
13 preds = [
14 ['O', 'O', 'B-ORG', 'O', 'O', 'O', 'O', 'O', 'O', 'O', 'O'],
15 ['B-LOC', 'O'],
16 ...
17 ...
18 ...
19 ]
20
21 precision, recall, f1 = evaluate(
22 itertools.chain(*labels),
23 itertools.chain(*preds)
24 )
Important: GPUs
Use Google Colab For the GPUs You do not necessarily need to write an
ipynb file, a py file works on Google Colab by using the following trick:
1. Upload the .py file to Google Colab. Let’s name it task1.py
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2. pip install all requirements:
1 !pip install datasets accelerate
3. run the task1.py in a colab cell using this line:
1 !python task1.py
Alternatively, you can use Github to push → clone to Colab.
If you cannot use Google Colab anymore, then Kaggle gives you 30 hours
a week worth of free GPUs (more than enough to complete this homework
15 times in a week). The free tier of Kaggle is better than Colab, but you
can only use the github push → clone trick on Kaggle.
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Task 1: Bidirectional LSTM model (40 points)
The first task is to build a simple bidirectional LSTM model for NER.
Implementing the bidirectional LSTM network with PyTorch. The architecture of the network is:
Embedding → BiLSTM → Linear → ELU → classifier
There is no flattening, the linear layer is run for every single hidden output
of the BiLSTM layer.
The hyper-parameters of the network are listed in the following table:
Layer hyperparam value
Embedding dim 100
Num LSTM layers 1
LSTM hidden dim 256
LSTM Dropout 0.33
Linear output dim 128
Table 2: Layer Specification
Train this BiLSTM model with the training data on NER with any optimizer
you like. Tune other parameters that are not specified in the above table,
such as batch size, learning rate, and learning rate scheduling.
Additionally, kindly provide answers to the following questions:
What are the precision, recall, and F1 score on the validation data?.
What are the precision, recall, and F1 score on the test data?
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Task 2: Using GloVe word embeddings (60
points)
Use the GloVe word embeddings to improve the BLSTM in Task 1. Helpful
link. The way we use the GloVe word embeddings is straightforward: we initialize the embeddings in our neural network with the corresponding vectors
in GloVe. Freeze the embeddings. Note that GloVe is case-insensitive,
but our NER model should be case-sensitive because capitalization
is important information for NER. You are asked to find a way to deal
with this conflict.
You may use the same solution to boost the score for Task 1.
Additionally, kindly provide answers to the following questions:
What is the precision, recall, and F1 score on the validation data?
What are the precision, recall, and F1 score on the test data?
BiLSTM with Glove Embeddings outperforms the model without. Can you
provide a rationale for this?
Bonus: The Transformer Encoder (40 points)
Transformer [2] is currently the most dominant architecture in NLP research.
Let’s apply the transformer to the CoNLL-2003 dataset.
Build a BERT-like model by stacking nn.TransformerEncoderLayer
Use Transformer Encoder to stack the transformer encoder layers: nn.TransformerEncoder
Define Positional Embedding for the transformer.
Define Token Embedding for the transformer.
Now define a class for your transformer model that uses:
1. Positional Embedding
2. Token Embedding
3. Transformer Encoder Stack
4. Linear Layer as a classifier
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Figure 1: Transformer Encoder
Layer hyperparam value
Embedding Size 128
num attention heads 8
sequence max length 128
feed-forward dimensions 128
Table 3: Transformer Specification
Do not forget to handle the src key padding mask, it is very important for
transformers.
The code from above links works when batch first=False.
This means that the input to the transformer is of the dimension
(sequence length, batch size, word vocab size)
This means that the output to the transformer is of the dimension
(sequence length, batch size, tag vocab size)
Additionally, provide answers to the following questions:
What is the precision, recall, and F1 score on the validation data?
What are the precision, recall, and F1 score on the test data?
What is the reason behind the poor performance of the transformer?
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Submission
Please follow the instructions and submit a zipped folder containing:
1. A PDF file that contains answers to the questions in the assignment
along with a clear description of your solution, including all the hyperparameters used in network architecture and model training.
2. Python code that only produces results on test data for task 1 (no
training). You may need to save your models for this.
3. Python code that only produces results on test data for task 2 (no
training). You may need to save your models for this.
4. README file to describe how to run your code to produce your results. In the README file, you need to provide the command line to
produce the prediction files. (We will execute your cmd to reproduce
your reported results on the test).
5. BONUS: The code you used.
References
[1] Jeffrey Pennington, Richard Socher, and Christopher D Manning. Glove:
Global vectors for word representation. In Proceedings of the 2014 conference on empirical methods in natural language processing (EMNLP),
pages 1532–1543, 2014.
[2] Ashish Vaswani, Noam Shazeer, Niki Parmar, Jakob Uszkoreit, Llion
Jones, Aidan N Gomez, Lukasz Kaiser, and Illia Polosukhin. Attention
is all you need. Advances in neural information processing systems, 30,
2017.
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