FastVLM: Self-Speculative Decoding for Fast Vision-Language Model Inference

Divya Jyoti Bajpai, Manjesh Kumar Hanawal


Abstract
Vision-language Models (VLMs) have made significant strides in visual understanding and query response generation, but often face challenges of high computational cost and inference latency due to autoregressive decoding. In this work, we introduce an imitation-learning-based Self-Speculative Decoding (SSD) framework, named FastVLM, to address these limitations. Our approach employs a lightweight draft model for token generation in an autoregressive manner, while a full model verifies these tokens non-autoregressively. Accepted tokens proceed seamlessly, while rejected tokens are corrected by the full model and used to guide the draft model’s refinement. Through an imitation network, FastVLM enhances the draft model by integrating deeper-level insights from the full model’s architecture. Also, it maintains the performance integrity of the full model while training the draft model, achieving a balance between efficiency and accuracy. Our method speeds up the inference process by 1.55-1.85× as compared to the final layer with minimal loss in performance. The source code is available at https://github.com/Div290/SSD.
Anthology ID:
2025.ijcnlp-long.64
Volume:
Proceedings of the 14th International Joint Conference on Natural Language Processing and the 4th Conference of the Asia-Pacific Chapter of the Association for Computational Linguistics
Month:
December
Year:
2025
Address:
Mumbai, India
Editors:
Kentaro Inui, Sakriani Sakti, Haofen Wang, Derek F. Wong, Pushpak Bhattacharyya, Biplab Banerjee, Asif Ekbal, Tanmoy Chakraborty, Dhirendra Pratap Singh
Venues:
IJCNLP | AACL
SIG:
Publisher:
The Asian Federation of Natural Language Processing and The Association for Computational Linguistics
Note:
Pages:
1166–1183
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URL:
https://preview.aclanthology.org/ingest-ijcnlp-aacl/2025.ijcnlp-long.64/
DOI:
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Cite (ACL):
Divya Jyoti Bajpai and Manjesh Kumar Hanawal. 2025. FastVLM: Self-Speculative Decoding for Fast Vision-Language Model Inference. In Proceedings of the 14th International Joint Conference on Natural Language Processing and the 4th Conference of the Asia-Pacific Chapter of the Association for Computational Linguistics, pages 1166–1183, Mumbai, India. The Asian Federation of Natural Language Processing and The Association for Computational Linguistics.
Cite (Informal):
FastVLM: Self-Speculative Decoding for Fast Vision-Language Model Inference (Bajpai & Hanawal, IJCNLP-AACL 2025)
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https://preview.aclanthology.org/ingest-ijcnlp-aacl/2025.ijcnlp-long.64.pdf