The difference of BERT, XLM-RoBERTa and Longformer

Tiya Vaj
2 min readFeb 29, 2024

BERT (Bidirectional Encoder Representations from Transformers), XLM-RoBERTa (Cross-lingual Language Model — RoBERTa), and Longformer are all transformer-based models used for natural language processing (NLP) tasks, but they have some key differences:

1. Model Architecture:
— BERT: BERT utilizes a bidirectional transformer architecture. It processes input sequences by jointly encoding all tokens bidirectionally.
— XLM-RoBERTa: XLM-RoBERTa is an extension of RoBERTa, which is itself an improvement over BERT. It employs a similar architecture to BERT but benefits from larger-scale pre-training and more aggressive training strategies.
— Longformer: Longformer is specifically designed for handling long sequences of text efficiently. It introduces a combination of sparse attention mechanisms and global attention to process longer sequences without significantly increasing computational requirements.

2. Handling of Long Sequences:
— BERT and XLM-RoBERTa have a maximum input sequence length, typically around 512 tokens. They struggle with processing longer sequences efficiently.
— Longformer, on the other hand, is designed to handle longer sequences, often up to tens of thousands of tokens, by employing sparse attention mechanisms and global attention. This makes Longformer more suitable for tasks involving long documents or text inputs.

3. Pre-training Data and Multilingual Support:
BERT was primarily pre-trained on English text data and initially targeted English-language tasks. However, it has been adapted and fine-tuned for various languages.
XLM-RoBERTa is a multilingual model trained on text data from multiple languages. It aims to provide robust performance across different languages without the need for language-specific models.
— Longformer is language-agnostic and can be trained on text data from any language. Its focus is more on efficiently processing long sequences rather than language-specific tasks.

4. Efficiency and Performance:
BERT and XLM-RoBERTa have been widely used and have demonstrated strong performance across various NLP tasks. However, they struggle with processing long sequences efficiently.
Longformer addresses the efficiency issue by enabling the processing of long sequences without significant computational overhead. This makes it particularly useful for tasks involving long documents or text inputs.

In summary, while BERT and XLM-RoBERTa are powerful transformer models widely used for NLP tasks, Longformer is specifically designed to handle long sequences efficiently, making it suitable for tasks involving lengthy documents or text inputs. Each model has its strengths and applications depending on the specific requirements of the NLP task at hand.



Tiya Vaj

Ph.D. Research Scholar in Informatics and my passionate towards data-driven for social good.Let's connect here