Layer Skip: Enabling Early Exit Inference and Self-Speculative Decoding
Authors: Mostafa Elhoushi, Akshat Shrivastava, Diana Liskovich, Basil Hosmer, Bram Wasti, Liangzhen Lai, Anas Mahmoud, Bilge Acun, Saurabh Agarwal, Ahmed Roman, Ahmed A Aly, Beidi Chen, Carole-Jean Wu
Abstract
We present LayerSkip, an end-to-end solution to speed-up inference of large language models (LLMs). First, during training we apply layer dropout, with low dropout rates for earlier layers and higher dropout rates for later layers, and an early exit loss where all transformer layers share the same exit. Second, during inference, we show that this training recipe increases the accuracy of early exit at earlier layers, without adding any auxiliary layers or modules to the model. Third, we present a novel self-speculative decoding solution where we exit at early layers and verify and correct with remaining layers of the model. Our proposed self-speculative decoding approach has less memory footprint than other speculative decoding approaches and benefits from shared compute and activations of the draft and verification stages. We run experiments on different Llama model sizes on different types of training: pretraining from scratch, continual pretraining, finetuning on specific data domain, and finetuning on specific task. We implement our inference solution and show speedups of up to 2.16x on summarization for CNN/DM documents, 1.82x on coding, and 2.0x on TOPv2 semantic parsing task.
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Closest papers
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ConfLayers: Adaptive Confidence-based Layer Skipping for Self-Speculative DecodingWalaa Amer, Udayan Das, Fadi J. Kurdahi · 2026 · arXiv.org · preprint, not peer reviewed · cited 3 times · Not summarized yet
Abstract
Self-speculative decoding is an inference technique for large language models designed to speed up generation without sacrificing output quality. It combines fast, approximate decoding using a compact version of the model as a draft model with selective re-evaluation by the full target model. Some existing methods form the draft model by dynamically learning which layers to skip during inference, effectively creating a smaller subnetwork to speed up computation. However, using heuristic-based approaches to select layers to skip can often be simpler and more effective. In this paper, we propose ConfLayers, a dynamic plug-and-play approach to forming the draft model in self-speculative decodin…
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AdaDecode: Accelerating LLM Decoding with Adaptive Layer ParallelismZhepei Wei, Wei-Lin Chen, Xin-Yu Zhu et al. · 2025 · International Conference on Machine Learning · cited 7 times · Not summarized yet
Abstract
Large language models (LLMs) are increasingly used for long-content generation (e.g., long Chain-of-Thought reasoning) where decoding efficiency becomes a critical bottleneck: Autoregressive decoding is inherently limited by its sequential token generation process, where each token must be generated before the next can be processed. This sequential dependency restricts the ability to fully leverage modern hardware's parallel processing capabilities. Existing methods like speculative decoding and layer skipping offer potential speedups but have notable drawbacks: speculative decoding relies on an auxiliary"drafter"model, which can be challenging to acquire and increases memory overhead, while…
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CLaSp: In-Context Layer Skip for Self-Speculative DecodingLong-Ze Chen, Renke Shan, Huiming Wang et al. · 2025 · Annual Meeting of the Association for Computational Linguistics · cited 14 times · Not summarized yet
Abstract
Speculative decoding (SD) is a promising method for accelerating the decoding process of Large Language Models (LLMs). The efficiency of SD primarily hinges on the consistency between the draft model and the verify model. However, existing drafting approaches typically require additional modules to be trained, which can be challenging to implement and ensure compatibility across various LLMs. In this paper, we propose CLaSp, an in-context layer-skipping strategy for self-speculative decoding. Unlike prior methods, CLaSp does not require additional drafting modules or extra training. Instead, it employs a plug-and-play mechanism by skipping intermediate layers of the verify model to construct…
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DEL: Context-Aware Dynamic Exit Layer for Efficient Self-Speculative DecodingH. E. Zarch, Lei Gao, Chao-Yi Jiang et al. · 2025 · arXiv.org · preprint, not peer reviewed · cited 10 times · Not summarized yet
Abstract
Speculative Decoding (SD) is a widely used approach to accelerate the inference of large language models (LLMs) without reducing generation quality. It operates by first using a compact model to draft multiple tokens efficiently, followed by parallel verification using the target LLM. This approach leads to faster inference compared to auto-regressive decoding. While there are multiple approaches to create a draft model, one promising approach is to use early-exit methods. These methods draft candidate tokens by using a subset of layers of the primary model and applying the remaining layers for verification, allowing a single model to handle both drafting and verification. While this techniq…
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Adaptive Layer-skipping in Pre-trained LLMsXuan Luo, Weizhi Wang, Xifeng Yan · 2025 · arXiv.org · preprint, not peer reviewed · cited 33 times · Not summarized yet
Abstract
Various layer-skipping methods have been proposed to accelerate token generation in large language models (LLMs). However, limited attention has been paid to a fundamental question: How do computational demands vary across the generation of different tokens? In this work, we introduce FlexiDepth, a method that dynamically adjusts the number of Transformer layers used in text generation. By incorporating a plug-in router and adapter, FlexiDepth enables adaptive computation in LLMs without modifying their original parameters. Applied to Llama-3-8B, it skips 8 out of 32 layers while maintaining full benchmark performance. Our experiments reveal that computational demands in LLMs significantly v…
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vSkipper: Translating Dynamic Layer Skipping into LLM Serving GainsDao-Min Wei, Yavuz Ferhatosmanoglu, E. Kalyvianaki · 2026 · Not summarized yet
Abstract
Dynamic layer skipping reduces LLM computation by allowing each token to execute only a subset of the model's layers. However, existing skippers rely on specialized generation loops and do not integrate with modern serving engines. As a result, fewer executed layers do not necessarily translate into lower serving latency: FlexiDepth skips 8 of Llama-3-8B's 32 layers on average, yet its standard generation loop decodes 14.6--21.0% more slowly than the base model. We present vSkipper, a virtualization layer that makes dynamic layer skippers pluggable in serving engines while preserving continuous batching, fixed-shape batches, paged KV caching, and captured decode graphs. At each routed layer,…
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SkipDecode: Autoregressive Skip Decoding with Batching and Caching for Efficient LLM InferenceLuciano Del Corro, Allison Del Giorno, Sahaj Agarwal et al. · 2023 · arXiv.org · preprint, not peer reviewed · cited 110 times · Not summarized yet
Abstract
Autoregressive large language models (LLMs) have made remarkable progress in various natural language generation tasks. However, they incur high computation cost and latency resulting from the autoregressive token-by-token generation. To address this issue, several approaches have been proposed to reduce computational cost using early-exit strategies. These strategies enable faster text generation using reduced computation without applying the full computation graph to each token. While existing token-level early exit methods show promising results for online inference, they cannot be readily applied for batch inferencing and Key-Value caching. This is because they have to wait until the las…
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The Diminishing Returns of Early-Exit Decoding in Modern LLMsRui Wei, R. Du, Han-Fei Yu et al. · 2026 · arXiv.org · preprint, not peer reviewed · cited 1 time · Not summarized yet
Abstract
In Large Language Model (LLM) inference, early-exit refers to stopping computation at an intermediate layer once the prediction is sufficiently confident, thereby reducing latency and cost. However, recent LLMs adopt improved pretraining recipes and architectures that reduce layer redundancy, potentially limiting early-exit opportunities. We re-evaluate layer-wise early-exit in modern LLMs and analyze how intermediate representations evolve during training. We introduce a metric to quantify a model's intrinsic suitability for early-exit and propose a benchmark for researchers to explore the potential early-exit benefits on different models and workloads. Our results show a diminishing trend …
Prior work it builds on
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SPEED: Speculative Pipelined Execution for Efficient DecodingC. Hooper, Sehoon Kim, Hiva Mohammadzadeh et al. · 2023 · arXiv.org · preprint, not peer reviewed · cited 58 times · Not summarized yet
Abstract
Generative Large Language Models (LLMs) based on the Transformer architecture have recently emerged as a dominant foundation model for a wide range of Natural Language Processing tasks. Nevertheless, their application in real-time scenarios has been highly restricted due to the significant inference latency associated with these models. This is particularly pronounced due to the autoregressive nature of generative LLM inference, where tokens are generated sequentially since each token depends on all previous output tokens. It is therefore challenging to achieve any token-level parallelism, making inference extremely memory-bound. In this work, we propose SPEED, which improves inference effic…
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Accelerating Large Language Model Decoding with Speculative SamplingCharlie Chen, Sebastian Borgeaud, Geoffrey Irving et al. · 2023 · arXiv.org · preprint, not peer reviewed · cited 1,258 times · Not summarized yet
Abstract
We present speculative sampling, an algorithm for accelerating transformer decoding by enabling the generation of multiple tokens from each transformer call. Our algorithm relies on the observation that the latency of parallel scoring of short continuations, generated by a faster but less powerful draft model, is comparable to that of sampling a single token from the larger target model. This is combined with a novel modified rejection sampling scheme which preserves the distribution of the target model within hardware numerics. We benchmark speculative sampling with Chinchilla, a 70 billion parameter language model, achieving a 2-2.5x decoding speedup in a distributed setup, without comprom…
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Fast Inference from Transformers via Speculative DecodingYaniv Leviathan, Matan Kalman, Yossi Matias · 2022 · Machine Learning · cited 2,306 times · AI summary available
Abstract
Inference from large autoregressive models like Transformers is slow - decoding K tokens takes K serial runs of the model. In this work we introduce speculative decoding - an algorithm to sample from autoregressive models faster without any changes to the outputs, by computing several tokens in parallel. At the heart of our approach lie the observations that (1) hard language-modeling tasks often include easier subtasks that can be approximated well by more efficient models, and (2) using speculative execution and a novel sampling method, we can make exact decoding from the large models faster, by running them in parallel on the outputs of the approximation models, potentially generating sev…
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Accelerating Training of Transformer-Based Language Models with Progressive Layer DroppingMinjia Zhang, Yu-Xiong He · 2020 · Neural Information Processing Systems · cited 126 times · Not summarized yet
Abstract
Recently, Transformer-based language models have demonstrated remarkable performance across many NLP domains. However, the unsupervised pre-training step of these models suffers from unbearable overall computational expenses. Current methods for accelerating the pre-training either rely on massive parallelism with advanced hardware or are not applicable to language modeling. In this work, we propose a method based on progressive layer dropping that speeds the training of Transformer-based language models, not at the cost of excessive hardware resources but from model architecture change and training technique boosted efficiency. Extensive experiments on BERT show that the proposed method ach…
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Confident Adaptive Language ModelingTal Schuster, Adam Fisch, Jai Gupta et al. · 2022 · Neural Information Processing Systems · cited 425 times · Not summarized yet
Abstract
Recent advances in Transformer-based large language models (LLMs) have led to significant performance improvements across many tasks. These gains come with a drastic increase in the models' size, potentially leading to slow and costly use at inference time. In practice, however, the series of generations made by LLMs is composed of varying levels of difficulty. While certain predictions truly benefit from the models' full capacity, other continuations are more trivial and can be solved with reduced compute. In this work, we introduce Confident Adaptive Language Modeling (CALM), a framework for dynamically allocating different amounts of compute per input and generation timestep. Early exit d…
Papers that cite it
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SEED: Self-Speculative Decoding via Implicit Encoder-DecoderHan-Kun Lin, Patrick Pynadath, Ruqi Zhang · 2026 · Not summarized yet
Abstract
Self-speculative decoding accelerates large language model (LLM) inference by drafting tokens from the target model itself, but faces a sharp tradeoff between the quality and cost of the draft. Early-exit methods produce drafts cheaply by terminating computation at intermediate layers, but forgo the deeper representations that later layers provide and thus suffer in draft quality. Multi-token prediction preserves draft quality by emitting from the model's final hidden states, but pays for a full forward pass to produce those states at every drafting step. We propose self-speculative encoder-decoder (SEED), a self-speculative method that obtains high-quality drafts cheaply by reusing the deep…
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Don't Drop Dropout: Optimizing Layer Sparsity for Efficient LLM Training and InferenceMostafa Elhoushi, Alexander D. Pretko, Nolan Dey et al. · 2026 · Not summarized yet
Abstract
Layer dropout (a.k.a. stochastic depth) has been shown to enable faster training, higher accuracy, and robustness to zero-shot layer pruning in both language and vision transformers. However, as models and datasets have scaled, dropout - particularly layer dropout - has largely disappeared from large language models (LLMs) pre-training recipes. While some prior work has reported that dropout can degrade accuracy, no comprehensive study has quantified, let alone mitigated, this effect. In this study, we show that layer dropout should be used in state-of-the-art LLM training, establishing best practices and scaling analysis for both training and post-training benefits. Concretely, with optimal…
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ECHO: Early-layer Collaborative Hierarchical Orchestration with Bonus Logits in Speculative DecodingZi-Yang Ma, Zi-Hong Zhang, Zu-Chao Li et al. · 2026 · cited 1 time · Not summarized yet
Abstract
While draft-model-free speculative decoding offers a promising path to efficient LLM inference, it is frequently constrained by stale draft candidates and the high computational cost of the verification. To address these challenges, we propose ECHO, a hierarchical dual-loop framework that exploits the functional asymmetry between LLM layers. Leveraging the high discriminative efficiency of early layers and the authoritative distribution of final layers, ECHO bifurcates inference into a high-frequency inner loop and a low-frequency outer loop. Within the inner loop, early-layer bonus logits drive rapid, multi-step draft-tree exploration at a minimal cost. Simultaneously, the outer loop perfor…
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Experience-Driven Dynamic Exits for LLMs with Reinforcement LearningYan-Yu Zhu, Hoilam Pao, Niu Hu et al. · 2026 · IEEE International Conference on Acoustics, Speech, and Signal Processing · Not summarized yet
Abstract
Large Language Models suffer from slow autoregressive inference. While self-speculative decoding accelerates this process, its efficiency is hampered by static configurations like fixed exit layers and speculation lengths. We reframe this optimization as a \textbf{Markov Decision Process} and propose \textbf{LEDE}, a framework that uses offline reinforcement learning. LEDE learns a policy to dynamically select the optimal exit layer and speculation length based on the local context of the generated sequence at each step, balancing computational cost and draft quality. Comprehensive evaluations on Llama-2 and Llama-3 models show LEDE achieves up to a $2.0\times$$\sim$$2.7\times$ speedup over …
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Deeper is Not Always Better: Mitigating the Alignment Tax via Confident Layer DecodingXuanming Zhang, Sining Zhoubian, Yuxuan Chen et al. · 2026 · arXiv.org · preprint, not peer reviewed · cited 3 times · Not summarized yet
Abstract
Autoregressive generation in large language models (LLMs) conventionally decodes from the final layer, assuming that deeper representations yield more reliable next-token predictions. We revisit this assumption by revealing a recurring Guess-Refine-Perturb dynamic: early layers form coarse guesses, intermediate layers refine reasoning-relevant semantics, and final layers can perturb these refined predictions toward generic or alignment-preferred tokens. We introduce Confident Decoding, a training-free decoding strategy that dynamically selects the most reliable near-final layer through entropy-guided conservative backward search. We further provide a theoretical formulation of layer selectio…
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Updated on 2 November 2026.