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CSCI544: Homework Assignment №2

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CSCI544: Homework Assignment №2
This assignment is an extension to HW assignment 1 on sentiment
analysis. Please follow the instructions and submit a zipped folder
containing:
1. A PDF containing a Jupyter Notebook response to the assignment. Your Jupyter Notebook should contain both code and text
cells with sufficient comments such that the reader can understand
your solution as well as your responses for some of the questions. On
the Jupyter notebook, please print the requested values, too. If it is
more convenient, you can also submit a PDF similar to assignment
1, i.e., initially explaining your solution and then merge a Jupyter
notebook.
2. You also need to submit your Jupyter Notebook separately in
.ipynb format such that it can be easily executed. Please include the
version of required dependencies. You can consider that data.tsv is a
raw dataset in the current directory that your notebook should read
and perform all the required steps and generate the desired outputs.
The preferred library to implement neural models is PyTorch but
TensorFlow (or Keras) is also acceptable. Please name your zipped
file “HW2-YourFirstName-YourLastName-AAA.zip”, where “AAA”
is either “Py” or “TF” depending on the library you have used. You
can also use publicly available implementations in portions of your
solution but you need to include proper reference to your resources,
e.g., url to the page that you used as a reference, books, etc.
1. Dataset Generation (5 points)
We will use the Amazon reviews dataset used in HW1. Load the dataset
and build a balanced dataset of 250K reviews along with their ratings (50K
instances per each rating score) through random selection. Create ternary
labels using the ratings. We assume that ratings more than 3 denote positive
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sentiment (class 1) and rating less than 3 denote negative sentiment (class
2). Reviews with rating 3 are considered to have neutral sentiment (class 3).
You can store your dataset after generation and reuse it to reduce the computational load. For your experiments consider a 80%/20% training/testing
split.
2. Word Embedding (30 points)
In this part the of the assignment, you will learn how to generate two sets
of Word2Vec features for the dataset you generated. You can use Gensim
library for this purpose. A helpful tutorial is available in the following link:
https://radimrehurek.com/gensim/auto_examples/tutorials/run_word2vec.
html
(a) (10 points)
Load the pretrained “word2vec-google-news-300” Word2Vec model and learn
how to extract word embeddings for your dataset. Try to check semantic
similarities of the generated vectors using two examples of your own, e.g.,
King − M an + W oman = Queen or excellent ∼ outstanding.
(b) (20 points)
Train a Word2Vec model using your own dataset. Set the embedding size
to be 300 and the window size to be 11. You can also consider a minimum
word count of 10. Check the semantic similarities for the same two examples
in part (a). What do you conclude from comparing vectors generated by
yourself and the pretrained model? Which of the Word2Vec models seems
to encode semantic similarities between words better?
3. Simple models (20 points)
Using the Word2Vec features that you can generate using the two models
you prepared in the Word Embedding section, train a perceptron and an
SVM model similar to HW1 for class 1 and class 2 (binary models). For this
purpose, you can just use the average Word2Vec vectors for each review as
the input feature (x =
1
N
PN
i=1 Wi
for a review with N words). To improve
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your performance, use the data cleaning and preprocessing steps of HW1
to include only important words from each review when you compute the
average x =
1
N
PN
i=1 Wi
. Report your accuracy values on the testing split for
these models for each feature type along with values you reported in your
HW1 submission, i.e., for each of perceptron and SVM, you need to report
three accuracy values for “word2vec-google-news-300”, your own Word2Vec,
and TF-IDF features.
What do you conclude from comparing performances for the models
trained using the three different feature types (TF-IDF, pretrained Word2Vec,
your trained Word2Vec)?
4. Feedforward Neural Networks (25 points)
Using the features that you can generate using the models you prepared in
the Word “Embedding section”, train a feedforward multilayer perceptron
network for sentiment analysis classification. Consider a network with two
hidden layers, each with 50 and 10 nodes, respectively. You can use cross
entropy loss and your own choice for other hyperparamters, e.g., nonlinearity,
number of epochs, etc. Part of getting good results is to select good values
for these hyperparamters.
You can also refer to the following tutorial to familiarize yourself:

Although the above tutorial is for image data but the concept of training
an MLP is very similar to what we want to do.
(a) (10 points)
To generate the input features, use the average Word2Vec vectors similar to
the “Simple models” section and train the neural network. Train a network
for binary classification using class 1 and class 2 and also a ternary model for
the three classes. Report accuracy values on the testing split for your MLP
model for each of the binary and ternary classification cases.
(b) (15 points)
To generate the input features, concatenate the first 10 Word2Vec vectors
for each review as the input feature (x = [WT
1
, …, WT
10]) and train the neural
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network. Report the accuracy value on the testing split for your MLP model
for each of the binary and ternary classification cases.
What do you conclude by comparing accuracy values you obtain with
those obtained in the “’Simple Models” section (note you can compare the
accuracy values for binary classification).
5. Convolutional Neural Networks (20 points)
Using the vectors you prepared in the “Word Embedding” section, train a
convolutional neural network (CNN) for sentiment analysis classification.
Train a simple CNN for sentiment analysis. You can consider an two-layer
CNN with the output channel sizes of 50 and 10. To feed your data into the
CNN, limit the maximum review length to 50 by truncating longer reviews
and padding shorter reviews with a null value (0). You can use cross entropy
loss and your own choice for other hyperparamters, e.g., nonlinearity, number
of epochs, etc. Train the CNN network for binary classification using class 1
and class 2 and also a ternary model for the three classes. Report accuracy
values on the testing split for your CNN model.
Note that in total, you need to report accuracy values for:
2 (number of Word2Vec models) * (2 (Perceptron + SVM) + 2 (binary/ternary settings) ( 2 (FNN) + 1 (CNN))) = 2 (2+ 2 (2 + 1)) = 16
cases.
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