#22 Nils Reimers on the Limits of Embeddings, Out-of-Domain Data, Long Context, Finetuning (and How We're Fixing It) | Search
Sep 19, 2024
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Join Nils Reimers, a prominent researcher in dense embeddings and the driving force behind foundational search models at Cohere. He dives into the intriguing limitations of text embeddings, such as their struggles with long documents and out-of-domain data. Reimers shares insights on the necessity of fine-tuning to adapt models effectively. He also discusses innovative approaches like re-ranking to enhance search relevance, and the bright future of embeddings as new research avenues are explored. Don't miss this deep dive into the cutting-edge of AI!
Text embeddings struggle with out-of-domain data and long documents, making fine-tuning essential for enhanced effectiveness in specific contexts.
The evolution of embeddings highlights the significance of leveraging existing models and employing two-stage retrieval processes for improved accuracy.
Deep dives
The Evolution of Embeddings
The discussion elaborates on the development of embeddings since the introduction of BERT, highlighting its application in argument mining and text clustering. Initially, pairwise classification was used to assess argument similarities, but scalability issues led to the exploration of embeddings for more efficient clustering. This evolution has enabled more effective semantic text processing and retrieval, indicating a significant shift towards unifying whether similar texts can be used for clustering and finding relevant answers based on a user's query. As the field progressed, better models emerged, including InferSent and innovations like contrastive learning, which improved the way embeddings are generated and assessed.
Performance Limitations of Embeddings
One significant discussion point centers on the limitations of text embeddings when applied outside their training domains. Notably, embeddings perform well only on data types and styles they have been trained on, encountering difficulties with unfamiliar or long-tail queries. This issue underscores the necessity for domain-specific evaluation sets, as users often struggle to define what constitutes 'similar' in various contexts. Fine-tuning or adapting embeddings to new contexts, rather than using them as out-of-the-box solutions, is essential to enhance their effectiveness and mitigate performance drops.
Methodologies for Effective Embedding Usage
The episode emphasizes that leveraging existing models instead of building new ones from scratch provides significant advantages in embedding tasks. It suggests that users should consider fine-tuning established embeddings on pairs of similar and dissimilar examples relevant to their particular use cases. Additionally, it discusses using a mixed approach to combine multiple embeddings, allowing for greater robustness compared to solely using the latest models, thus providing a strategy for effective classification and retrieval. Such approaches recognize the complexity of tasks and the varying preferences of users, making tailored implementations a necessity.
Addressing Challenges with Long Documents
Challenges linked to encoding and retrieving information from long documents are explored, particularly concerning the limitations of current embedding methods. While models can technically handle longer contexts, they often fail to retain critical details, especially as document length increases. This reinforces the point that embeddings provide only a high-level gist of the text, missing finer details essential for thorough comprehension. The recommendation to use a two-stage process for document retrieval ensures initial filtering followed by re-ranking to focus on specific details, thus maintaining higher accuracy in information retrieval.
Text embeddings have limitations when it comes to handling long documents and out-of-domain data.
Today, we are talking to Nils Reimers. He is one of the researchers who kickstarted the field of dense embeddings, developed sentence transformers, started HuggingFace’s Neural Search team and now leads the development of search foundational models at Cohere. Tbh, he has too many accolades to count off here.
We talk about the main limitations of embeddings:
Failing out of domain
Struggling with long documents
Very hard to debug
Hard to find formalize what actually is similar
Are you still not sure whether to listen? Here are some teasers:
Interpreting embeddings can be challenging, and current models are not easily explainable.
Fine-tuning is necessary to adapt embeddings to specific domains, but it requires careful consideration of the data and objectives.
Re-ranking is an effective approach to handle long documents and incorporate additional factors like recency and trustworthiness.
The future of embeddings lies in addressing scalability issues and exploring new research directions.
text embeddings, limitations, long documents, interpretation, fine-tuning, re-ranking, future research
00:00 Introduction and Guest Introduction 00:43 Early Work with BERT and Argument Mining 02:24 Evolution and Innovations in Embeddings 03:39 Constructive Learning and Hard Negatives 05:17 Training and Fine-Tuning Embedding Models 12:48 Challenges and Limitations of Embeddings 18:16 Adapting Embeddings to New Domains 22:41 Handling Long Documents and Re-Ranking 31:08 Combining Embeddings with Traditional ML 45:16 Conclusion and Upcoming Episodes
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