Spec-LLaVA: Accelerating Vision-Language Models with Dynamic Tree-Based Speculative Decoding

Fuente: arXiv
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Auteurs principaux: Huo, Mingxiao, Zhang, Jiayi, Wang, Hewei, Xu, Jinfeng, Chen, Zheyu, Tai, Huilin, Chen, Yijun
Format: Preprint
Publié: 2025
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author Huo, Mingxiao
Zhang, Jiayi
Wang, Hewei
Xu, Jinfeng
Chen, Zheyu
Tai, Huilin
Chen, Yijun
author_facet Huo, Mingxiao
Zhang, Jiayi
Wang, Hewei
Xu, Jinfeng
Chen, Zheyu
Tai, Huilin
Chen, Yijun
contents Vision-Language Models (VLMs) enable powerful multimodal reasoning but suffer from slow autoregressive inference, limiting their deployment in real-time applications. We introduce Spec-LLaVA, a system that applies speculative decoding to accelerate VLMs without sacrificing output quality. Spec-LLaVA pairs a lightweight draft VLM with a large target model: the draft speculates future tokens, which the target verifies in parallel, allowing multiple tokens to be generated per step. To maximize efficiency, we design a dynamic tree-based verification algorithm that adaptively expands and prunes speculative branches using draft model confidence. On MS COCO out-of-domain images, Spec-LLaVA achieves up to 3.28$\times$ faster decoding on LLaVA-1.5 (7B, 13B) with no loss in generation quality. This work presents a lossless acceleration framework for VLMs using dynamic tree-structured speculative decoding, opening a path toward practical real-time multimodal assistants. Importantly, the lightweight draft model design makes the framework amenable to resource-constrained or on-device deployment settings.
format Preprint
id arxiv_https___arxiv_org_abs_2509_11961
institution arXiv
publishDate 2025
record_format arxiv
spellingShingle Spec-LLaVA: Accelerating Vision-Language Models with Dynamic Tree-Based Speculative Decoding
Huo, Mingxiao
Zhang, Jiayi
Wang, Hewei
Xu, Jinfeng
Chen, Zheyu
Tai, Huilin
Chen, Yijun
Computation and Language
Vision-Language Models (VLMs) enable powerful multimodal reasoning but suffer from slow autoregressive inference, limiting their deployment in real-time applications. We introduce Spec-LLaVA, a system that applies speculative decoding to accelerate VLMs without sacrificing output quality. Spec-LLaVA pairs a lightweight draft VLM with a large target model: the draft speculates future tokens, which the target verifies in parallel, allowing multiple tokens to be generated per step. To maximize efficiency, we design a dynamic tree-based verification algorithm that adaptively expands and prunes speculative branches using draft model confidence. On MS COCO out-of-domain images, Spec-LLaVA achieves up to 3.28$\times$ faster decoding on LLaVA-1.5 (7B, 13B) with no loss in generation quality. This work presents a lossless acceleration framework for VLMs using dynamic tree-structured speculative decoding, opening a path toward practical real-time multimodal assistants. Importantly, the lightweight draft model design makes the framework amenable to resource-constrained or on-device deployment settings.
title Spec-LLaVA: Accelerating Vision-Language Models with Dynamic Tree-Based Speculative Decoding
topic Computation and Language
url https://arxiv.org/abs/2509.11961