Beyond Next-Token Prediction: A Performance Characterization of Diffusion versus Autoregressive Language Models
https://machinelearning.apple.com/research/diffusion-autoregressive-performance📌 【Apple ML 研究】Diffusion 與 Autoregressive 模型性能對比:並行生成的優勢與長文本挑戰
TL;DR:研究指出 Diffusion 模型具備更高算術強度,但在長文本擴展性與批次吞吐量上仍遜於 Autoregressive 模型。
🤔 逐字預測的瓶頸:序列依賴與低算術強度
目前的 LLM 主流架構是 Autoregressive Language Models (ARMs),這類模型依賴於「下一字預測」(next-token prediction),必須根據已生成的 token 序列逐一生成下一個 token。這種內建的序列依賴性導致了推論時的算術強度(arithmetic intensity)較低,限制了硬體效能的發揮。
🧩 Diffusion 模型的潛力:並行生成的機會
為了突破序列生成的限制,Diffusion Language Models (DLMs) 成為一種具備潛力的替代架構。DLMs 的核心差異在於它可以並行生成輸出 token,藉由利用 token 位置間的並行性,DLMs 能展現出比 ARMs 更高的算術強度。
📊 性能對比:並行性與擴展性的權衡
研究透過理論分析與實證分析,揭示了兩者在不同維度的表現差異:
- 長文本擴展性:雖然 DLMs 具備並行優勢,但在處理長文本時,其擴展性表現不如 ARMs。
- 批次推論效能:在進行批次推論(batched inference)時,ARMs 表現更佳,因為它們能更有效地利用批次中不同序列間的並行性,從而獲得更高的吞吐量(throughput)。
💡 解決方案:透過 Block-wise Decoding 提升擴展性
為了讓 DLMs 能像 ARMs 一樣有效處理長文本,研究探索了「分塊解碼」(block-wise decoding)技術。這種方法將算術強度與序列長度解耦(decouple),進而讓 DLM 在長文本場景下擁有更好的擴展能力。
⚠️ DLM 的關鍵優化方向:減少採樣步數
研究強調,若要讓開源 DLM 在延遲(latency)表現上超越 ARMs,減少採樣步數(sampling steps)是關鍵的優化機會。
🎯 實務啟示
對於開發者而言,若追求極高的推論吞吐量,目前的 ARMs 仍具優勢;但若希望發揮硬體並行效能,開發更高效的 DLM 採樣演算法(減少採樣步數)並結合分塊解碼技術,將是實現低延遲並行生成的關鍵路徑。
🔗 來源
- 標題:Beyond Next-Token Prediction: A Performance Characterization of Diffusion versus Autoregressive Language Models
- 作者/機構:Minseo Kim, Coleman Hooper, Aditya Tomar, Chenfeng Xu, Mehrdad Farajtabar, Michael W. Mahoney, Kurt Keutzer, Amir Gholami @ Apple ML / Seoul National University / UC Berkeley / UT Austin / ICSI / LBNL
- 連結:https://machinelearning.apple.com/research/diffusion-autoregressive-performance
#LLM #DiffusionModels #AutoregressiveModels #NLP #MachineLearning #InferenceOptimization #ParallelGeneration #AIResearch #AppleML #DeepLearning
原始資料 Apple ML · 收集於 2026-08-08
摘要原文
research area Speech and Natural Language Processing content type paper published August 2026 Beyond Next-Token Prediction: A Performance Characterization of Diffusion versus Autoregressive Language Models Authors Minseo Kim†, Coleman Hooper‡, Aditya Tomar‡, Chenfeng Xu‡††, Mehrdad Farajtabar, Michael W. Mahoney‡§¶, Kurt Keutzer‡, Amir Gholami‡§* View publication Copy Bibtex Large Language Models (LLMs) have achieved state-of-the-art performance on a broad range of Natural Language Processing (NLP) tasks, including document processing and code generation. Autoregressive Language Models (ARMs), which generate tokens sequentially conditioned on all previous tokens, have been the predominant paradigm for LLMs. While these models have achieved high accuracy across a range of downstream tasks, they exhibit low arithmetic intensity due to the inherent sequential dependency in next-token prediction. Recently, Diffusion Language Models (DLMs) have emerged as a promising alternative architecture. DLMs generate output tokens in parallel, mitigating the limitations of sequential decoding. However, the performance implications of DLMs relative to commonly deployed ARMs are not fully understood. In this work, we present a comprehensive study of the performance characteristics of ARMs and DLMs, combining theoretical analysis with empirical profiling to characterize the trade-offs between these approaches. We show that although DLMs can achieve higher arithmetic intensity than ARMs by leveraging parallelism across token positions, they fail to scale effectively with longer contexts. We then explore block-wise decoding for DLMs, which decouples arithmetic intensity from sequence length and enables better scaling to long contexts (similar to ARMs). We also examine batched inference and find that ARMs exhibit superior throughput as they benefit more from parallelism across sequences in the batch. Finally, we highlight opportunities for accelerating DLM inference, emphasizing that reducing the number of sampling steps is key for open-source DLMs to achieve lower latency relative to ARMs. † Seoul National University ‡ University of California, Berkeley § ICSI ¶ LBNL †† University of Texas at Austin * Advisory role Related readings and updates. Your LLM Knows the Future: Uncovering Its Multi-Token Prediction Potential August 8, 2025 research area Methods and Algorithms , research area Speech and Natural Language Processing Autoregressive language models are constrained by their inherently sequential nature, generating one token at a time. This paradigm limits inference speed and parallelism, especially during later stages of generation when the direction and semantics of text are relatively certain. In this work, we propose a novel framework that leverages the inherent knowledge of vanilla autoregressive language models about future tokens, combining techniques to… Read more Scaling Diffusion Language Models via Adaptation from Autoregressive Models April 16, 2025 research area Speech and Natural Language Processing conference ICLR Diffusion Language Models (DLMs) have emerged as a promising new paradigm for text generative modeling, potentially addressing limitations of autoregressive (AR) models. However, current DLMs have been studied at a smaller scale compared to their AR counterparts and lack fair comparison on language modeling benchmarks. Additionally, training diffusion models from scratch at scale remains challenging. Given the prevalence of open-source AR… Read more Discover opportunities in Machine Learning. Our research in machine learning breaks new ground every day. Work with us
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