SUGAR: Spectral and Geometry-Aware Alignment for Matryoshka Representation Distillation

Hai An Vu, Phung Gia Huy, Minh-Phuc Truong, Linh Ngo Van, Thanh Hong Nguyen, Thanh-Toan Do, Trung Le


Abstract
Matryoshka Representation Learning (MRL) produces nested embeddings whose prefixes remain semantically meaningful, allowing representations to be truncated at inference time and enabling a single model to operate across multiple dimensional budgets. This paradigm has been adopted in several modern embedding models such as Qwen3-Embedding and OpenAI text-embedding-3. However, distilling MRL teachers into compact students remains largely unexplored, as conventional knowledge distillation methods focus on aligning single-scale embeddings and do not account for the multi-scale structure of Matryoshka representations. We introduce Matryoshka Representation Distillation and propose SUGAR, a new framework that preserves the structural properties of MRL embeddings during knowledge distillation. SUGAR aligns point-wise semantic fidelity, spectral capacity via effective-rank matching, and global subspace geometry through Grassmannian alignment. Our extensive experiments show that SUGAR produces compact students that retain strong performance across multiple embedding dimensions while preserving deployment flexibility.
Anthology ID:
2026.emnlp-main.228
Volume:
Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing
Month:
October
Year:
2026
Address:
Budapest, Hungary
Editors:
Hung-Yi Lee, Sunipa Dev, Jessy Li, Desmond Elliott
Venue:
EMNLP
SIG:
SIGDAT
Publisher:
Association for Computational Linguistics
Note:
Pages:
5257–5271
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URL:
https://aclanthology.org/2026.emnlp-main.228/
DOI:
Bibkey:
Cite (ACL):
Hai An Vu, Phung Gia Huy, Minh-Phuc Truong, Linh Ngo Van, Thanh Hong Nguyen, Thanh-Toan Do, and Trung Le. 2026. SUGAR: Spectral and Geometry-Aware Alignment for Matryoshka Representation Distillation. In Proceedings of the 2026 Conference on Empirical Methods in Natural Language Processing, pages 5257–5271, Budapest, Hungary. Association for Computational Linguistics.
Cite (Informal):
SUGAR: Spectral and Geometry-Aware Alignment for Matryoshka Representation Distillation (Vu et al., EMNLP 2026)
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PDF:
https://aclanthology.org/2026.emnlp-main.228.pdf