SPA-Cache: Singular Proxies for Adaptive Caching in Diffusion Language Models

Fuente: arXiv
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Autores principales: Sun, Wenhao, Tu, Rong-Cheng, Ding, Yifu, Jin, Zhao, Liao, Jingyi, Jing, Yongcheng, Tao, Dacheng
Formato: Preprint
Publicado: 2026
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author Sun, Wenhao
Tu, Rong-Cheng
Ding, Yifu
Jin, Zhao
Liao, Jingyi
Jing, Yongcheng
Tao, Dacheng
author_facet Sun, Wenhao
Tu, Rong-Cheng
Ding, Yifu
Jin, Zhao
Liao, Jingyi
Jing, Yongcheng
Tao, Dacheng
contents While Diffusion Language Models (DLMs) offer a flexible, arbitrary-order alternative to the autoregressive paradigm, their non-causal nature precludes standard KV caching, forcing costly hidden state recomputation at every decoding step. Existing DLM caching approaches reduce this cost by selective hidden state updates; however, they are still limited by (i) costly token-wise update identification heuristics and (ii) rigid, uniform budget allocation that fails to account for heterogeneous hidden state dynamics. To address these challenges, we present SPA-Cache that jointly optimizes update identification and budget allocation in DLM cache. First, we derive a low-dimensional singular proxy that enables the identification of update-critical tokens in a low-dimensional subspace, substantially reducing the overhead of update identification. Second, we introduce an adaptive strategy that allocates fewer updates to stable layers without degrading generation quality. Together, these contributions significantly improve the efficiency of DLMs, yielding up to an $8\times$ throughput improvement over vanilla decoding and a $2$--$4\times$ speedup over existing caching baselines.
format Preprint
id arxiv_https___arxiv_org_abs_2602_02544
institution arXiv
publishDate 2026
record_format arxiv
spellingShingle SPA-Cache: Singular Proxies for Adaptive Caching in Diffusion Language Models
Sun, Wenhao
Tu, Rong-Cheng
Ding, Yifu
Jin, Zhao
Liao, Jingyi
Jing, Yongcheng
Tao, Dacheng
Machine Learning
Artificial Intelligence
While Diffusion Language Models (DLMs) offer a flexible, arbitrary-order alternative to the autoregressive paradigm, their non-causal nature precludes standard KV caching, forcing costly hidden state recomputation at every decoding step. Existing DLM caching approaches reduce this cost by selective hidden state updates; however, they are still limited by (i) costly token-wise update identification heuristics and (ii) rigid, uniform budget allocation that fails to account for heterogeneous hidden state dynamics. To address these challenges, we present SPA-Cache that jointly optimizes update identification and budget allocation in DLM cache. First, we derive a low-dimensional singular proxy that enables the identification of update-critical tokens in a low-dimensional subspace, substantially reducing the overhead of update identification. Second, we introduce an adaptive strategy that allocates fewer updates to stable layers without degrading generation quality. Together, these contributions significantly improve the efficiency of DLMs, yielding up to an $8\times$ throughput improvement over vanilla decoding and a $2$--$4\times$ speedup over existing caching baselines.
title SPA-Cache: Singular Proxies for Adaptive Caching in Diffusion Language Models
topic Machine Learning
Artificial Intelligence
url https://arxiv.org/abs/2602.02544