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arxiv:2509.04185

Set Block Decoding is a Language Model Inference Accelerator

Published on Sep 4
· Submitted by itaigat on Sep 8
#2 Paper of the day
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Abstract

Set Block Decoding accelerates language model generation by integrating next token prediction and masked token prediction, enabling parallel sampling of future tokens and reducing computational cost without sacrificing accuracy.

AI-generated summary

Autoregressive next token prediction language models offer powerful capabilities but face significant challenges in practical deployment due to the high computational and memory costs of inference, particularly during the decoding stage. We introduce Set Block Decoding (SBD), a simple and flexible paradigm that accelerates generation by integrating standard next token prediction (NTP) and masked token prediction (MATP) within a single architecture. SBD allows the model to sample multiple, not necessarily consecutive, future tokens in parallel, a key distinction from previous acceleration methods. This flexibility allows the use of advanced solvers from the discrete diffusion literature, offering significant speedups without sacrificing accuracy. SBD requires no architectural changes or extra training hyperparameters, maintains compatibility with exact KV-caching, and can be implemented by fine-tuning existing next token prediction models. By fine-tuning Llama-3.1 8B and Qwen-3 8B, we demonstrate that SBD enables a 3-5x reduction in the number of forward passes required for generation while achieving same performance as equivalent NTP training.

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Paper submitter
edited 2 days ago

We present a new paradigm called Set Block Decoding, combining next-token-prediction and masked (or discrete diffusion) models, allowing parallel decoding (x3-5 speedup) without any architectural changes and with exact KV cache. Matches NTP performance!

Absolutely phenomenal results, folks - congratulations, and thank you both for this amazing work and sharing it with the world!
One quip: Figure 1 is a data vizualization chart crime. The horizontal axis starting at 1 means that you can't actually visually compare SBD against NTP — should start at 0 instead. Additionally, "Speedup" is a rather poor choice for the horizontal axis label, as the word can be interpreted as delta improvement — a better choice being something like "Speed Factor" or "Speed wrpt/NTP", etc.

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Great work

Great work! Will the training and inference code be open-sourced?

Is there a SBD fine-tuned llama-3b available to download? As presented in the paper?

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