arXiv Machine Learning By Yuzheng Lan

Speculative Decoding for Mixture-of-Experts Models: Expert Bytes, Kernel Bandwidth and the Best Draft Length

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The paper investigates speculative decoding for mixture‑of‑experts (MoE) language models, focusing on how deduplication of expert reads can reduce byte traffic and improve decoding speed. By modeling step time as a function of bytes requested and kernel bandwidth, the authors derive conditions under which speculation outperforms plain decoding and identify the optimal draft length as a staircase function of acceptance rate. Experiments on llama.cpp Metal, MLX‑LM, and llama.cpp CUDA show that deduplication is only faster for very short draft lengths (5–8 tokens) or not at all, and the predicted crossover points closely match measured savings across multiple configurations.

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