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Measured on real Apple Silicon: KV-cache pruning speeds up to 1.75x, but every speculative decoding method they tested made it slower

AspireAI community · arXiv (NeurIPS 2026 ODI + SLM-Agents workshops)
Most inference optimisations are benchmarked on server-class NVIDIA GPUs under batched serving, so this paper evaluated four families on four Apple machines under a single-request decode workload, with matched RTX 4090 comparisons where possible. KV-cache pruning reached up to 1.75 times end-to-end throughput on Apple, but could reduce throughput on desktop NVIDIA GPUs. Every speculative decoding method they evaluated reduced throughput on Apple, despite reported 2 to 6 times gains on server GPUs. CUDA kernel designs transferred only partially, since public Metal lacks asynchronous copy and batch-one decode makes several serving mechanisms inapplicable, though transferable components yielded up to 1.20 times decode throughput. Quantisation gains varied by machine. The paper's conclusion is the useful part: a reported speedup is a joint function of technique, runtime, hardware contract and workload, not a property of the technique alone.
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