RahulBhalley / sentiment-analysis-bert.pytorch

IMDB Sentiment Analysis with BERT

Assignment: Sentiment Analysis with BERT Model

Problem statement

The goal is to train a deep neural network to predict the sentiment of (hate) speech text.

Solution

This problem was solved by training a recent text classification model called BERT (Bidirectional Encoder Representations from Transformers).

The pretrained model was loaded from Hugging Faces' transformers. Then a two layer bidirectional nn.GRU sub-networks was appended at BERT's out. When input tokenized ids of text are passed through BERT then it outputs a representation (also called embedding in this case). This representation is then passed through GRU layers. Following the time-step from GRU the last time-step's hidden state is extracted and then passed through a logistic classifier (using nn.Linear module). Following this we train the model using nn.BCEWithLogitsLoss loss.

We used IMDB dataset instead of using some specific hate speech dataset. Surprisingly the model still nicely classifies the hate speech.

Future work

1. Training on an actual hate speech (text) dataset, instead of IMDB sentiment dataset, will give better accuracy for predicting sentiment of hate speech.
2. This BERT model can be trained longer to see if the accuracy improves further.
3. One can choose to train some other recent SOTA Transformer models such as Longformer, Electra, etc. for sentiment classification.

Results

Train accuracy: 93.17%

Train loss: 0.180

Test accuracy: 92.24%

Test loss: 0.198

Validation accuracy: 91.26%

Validation loss: 0.219

How to run this code

Clone this repo:

git clone https://github.com/RahulBhalley/sentiment-analysis-bert.pytorch
cd sentiment-analysis-bert.pytorch/

Install the dependencies

All dependencies are listed in requirements.txt. Please install them with the following command.

sudo pip3 install -r requirements.txt

Usage

For both training and inferencing the BERT model you only need to run the following code.

python3 main.py

All you need to do is make changes to variables in config.py for controlling the behavior of this program.

Following is a list of settings and their descriptions:

• TRAIN: set True to train BERT model but for inference set it to False
• TEXT: a string whose sentiment is predicted when infering the model
• BATCH_SIZE: (default: 128) batch size of train examples to use during training.
• N_EPOCHS: (default: 05) total epochs to train the model for.
• SEED: (default: 12345) the seed value to make experiments reproducible.
• BIDIRECTIONAL: set True for bidirectional nn.GRU otherwise False.
• HIDDEN_DIM: (default: 256)hidden dimensions for nn.GRU.
• OUTPUT_DIM: (default: 1, don't change) since sentiment is binary output.
• N_LAYERS: (default: 2) number of layers of nn.GRU layer.
• DROPOUT: (default: 0.25) dropout rate.

For example, to make sentiment predictions (i.e. inference) simply set TRAIN = False in config.py. Also provide the text to TEXT variable in config.py. This will load the trained parameters model.pt and make prediction.

Note: The output closer to 1 means hate speech whereas in case of close to 0 means the content of text is good/happy.

For TEXT = 'I like you!', the sentiment is closer to 0 (exactly 0.13519087433815002).

But when TEXT = 'I hate you!' then the sentiment is close to 1 (exactly 0.7887630462646484).

In order to train the model just keep TRAIN = True in config.py and run python3 main.py.