Transformer Models for MATLAB

This repository implements deep learning transformer models in MATLAB.

Requirements

BERT and FinBERT

• MATLAB R2021a or later
• Deep Learning Toolbox
• Text Analytics Toolbox

GPT-2

• MATLAB R2020a or later
• Deep Learning Toolbox

Getting Started

Download or clone this repository to your machine and open it in MATLAB.

Functions

bert

mdl = bert loads a pretrained BERT transformer model and if necessary, downloads the model weights. The output mdl is structure with fields Tokenizer and Parameters that contain the BERT tokenizer and the model parameters, respectively.

mdl = bert("Model",modelName) specifies which BERT model variant to use:

• "base" (default) - A 12 layer model with hidden size 768.
• "multilingual-cased" - A 12 layer model with hidden size 768. The tokenizer is case-sensitive. This model was trained on multi-lingual data.
• "medium" - An 8 layer model with hidden size 512.
• "small" - A 4 layer model with hidden size 512.
• "mini" - A 4 layer model with hidden size 256.
• "tiny" - A 2 layer model with hidden size 128.

bert.model

Z = bert.model(X,parameters) performs inference with a BERT model on the input 1-by-numInputTokens-by-numObservations array of encoded tokens with the specified parameters. The output Z is an array of size (NumHeads*HeadSize)-by-numInputTokens-by-numObservations. The element Z(:,i,j) corresponds to the BERT embedding of input token X(1,i,j).

Z = bert.model(X,parameters,Name,Value) specifies additional options using one or more name-value pairs:

• "PaddingCode" - Positive integer corresponding to the padding token. The default is 1.
• "InputMask" - Mask indicating which elements to include for computation, specified as a logical array the same size as X or as an empty array. The mask must be false at indices positions corresponds to padding, and true elsewhere. If the mask is [], then the function determines padding according to the PaddingCode name-value pair. The default is [].
• "DropoutProb" - Probability of dropout for the output activation. The default is 0.
• "AttentionDropoutProb" - Probability of dropout used in the attention layer. The default is 0.
• "Outputs" - Indices of the layers to return outputs from, specified as a vector of positive integers, or "last". If "Outputs" is "last", then the function returns outputs from the final encoder layer only. The default is "last".
• "SeparatorCode" - Separator token specified as a positive integer. The default is 103.

finbert

mdl = finbert loads a pretrained BERT transformer model for sentiment analysis of financial text. The output mdl is structure with fields Tokenizer and Parameters that contain the BERT tokenizer and the model parameters, respectively.

mdl = finbert("Model",modelName) specifies which FinBERT model variant to use:

• "sentiment-model" (default) - The fine-tuned sentiment classifier model.
• "language-model" - The FinBERT pretrained language model, which uses a BERT-Base architecture.

finbert.sentimentModel

sentiment = finbert.sentimentModel(X,parameters) classifies the sentiment of the input 1-by-numInputTokens-by-numObservations array of encoded tokens with the specified parameters. The output sentiment is a categorical array with categories "positive", "neutral", or "negative".

[sentiment, scores] = finbert.sentimentModel(X,parameters) also returns the corresponding sentiment scores in the range [-1 1].

gpt2

mdl = gpt2 loads a pretrained GPT-2 transformer model and if necessary, downloads the model weights.

generateSummary

summary = generateSummary(mdl,text) generates a summary of the string or char array text using the transformer model mdl. The output summary is a char array.

summary = generateSummary(mdl,text,Name,Value) specifies additional options using one or more name-value pairs.

• "MaxSummaryLength" - The maximum number of tokens in the generated summary. The default is 50.
• "TopK" - The number of tokens to sample from when generating the summary. The default is 2.
• "Temperature" - Temperature applied to the GPT-2 output probability distribution. The default is 1.
• "StopCharacter" - Character to indicate that the summary is complete. The default is ".".

Example: Classify Text Data Using BERT

The simplest use of a pretrained BERT model is to use it as a feature extractor. In particular, you can use the BERT model to convert documents to feature vectors which you can then use as inputs to train a deep learning classification network.

The example ClassifyTextDataUsingBERT.m shows how to use a pretrained BERT model to classify failure events given a data set of factory reports.

Example: Fine-Tune Pretrained BERT Model

To get the most out of a pretrained BERT model, you can retrain and fine tune the BERT parameters weights for your task.

The example FineTuneBERT.m shows how to fine-tune a pretrained BERT model to classify failure events given a data set of factory reports.

Example: Analyze Sentiment with FinBERT

FinBERT is a sentiment analysis model trained on financial text data and fine-tuned for sentiment analysis.

The example SentimentAnalysisWithFinBERT.m shows how to classify the sentiment of financial news reports using a pretrained FinBERT model.

Example: Predict Masked Tokens Using BERT and FinBERT

BERT models are trained to perform various tasks. One of the tasks is known as masked language modeling which is the task of predicting tokens in text that have been replaced by a mask value.

The example PredictMaskedTokensUsingBERT.m shows how to predict masked tokens and calculate the token probabilities using a pretrained BERT model.

The example PredictMaskedTokensUsingFinBERT.m shows how to predict masked tokens for financial text using and calculate the token probabilities using a pretrained FinBERT model.

Example: Summarize Text Using GPT-2

Transformer networks such as GPT-2 can be used to summarize a piece of text. The trained GPT-2 transformer can generate text given an initial sequence of words as input. The model was trained on comments left on various web pages and internet forums.

Because lots of these comments themselves contain a summary indicated by the statement "TL;DR" (Too long, didn't read), you can use the transformer model to generate a summary by appending "TL;DR" to the input text. The generateSummary function takes the input text, automatically appends the string "TL;DR" and generates the summary.

The example SummarizeTextUsingTransformersExample.m shows how to summarize a piece of text using GPT-2.