NV-Embed: Improved Techniques for Training LLMs as Generalist Embedding
  Models
Authors: name: Chankyu Lee; name: Rajarshi Roy; name: Mengyao Xu; name: Jonathan Raiman; name: Mohammad Shoeybi; name: Bryan Catanzaro; name: Wei Ping
Published: 2024-05-27 17:59:45

Abstract: Decoder-only large language model (LLM)-based embedding models are beginning
to outperform BERT or T5-based embedding models in general-purpose text
embedding tasks, including dense vector-based retrieval. In this work, we
introduce the NV-Embed model with a variety of architectural designs and
training procedures to significantly enhance the performance of LLM as a
versatile embedding model, while maintaining its simplicity and
reproducibility. For model architecture, we propose a latent attention layer to
obtain pooled embeddings, which consistently improves retrieval and downstream
task accuracy compared to mean pooling or using the last <EOS> token embedding
from LLMs. To enhance representation learning, we remove the causal attention
mask of LLMs during contrastive training. For model training, we introduce a
two-stage contrastive instruction-tuning method. It first applies contrastive
training with instructions on retrieval datasets, utilizing in-batch negatives
and curated hard negative examples. At stage-2, it blends various non-retrieval
datasets into instruction tuning, which not only enhances non-retrieval task
accuracy but also improves retrieval performance. Combining these techniques,
our NV-Embed model, using only publicly available data, has achieved a
record-high score of 69.32, ranking No. 1 on the Massive Text Embedding
Benchmark (MTEB) (as of May 24, 2024), with 56 tasks, encompassing retrieval,
reranking, classification, clustering, and semantic textual similarity tasks.
Notably, our model also attains the highest score of 59.36 on 15 retrieval
tasks in the MTEB benchmark (also known as BEIR). We will open-source the model
at: https://huggingface.co/nvidia/NV-Embed-v1.