Adds the memory-bound mirror of the compute-bound prefill figure. New single-rank decode sweep (T_q=1, M=8) reuses the prefill_compute_bound kernels, sweeping per-rank S_kv with NO cross-CUBE reduce — isolating the local attention that the 64-way Case-6 decode masks under its reduce tail.
Finding: even memory-bound decode benefits from the composite command. Its scheduler-streamed concurrent per-tile DMAs reach ~233 GB/s (91% of the 256 GB/s per-rank roofline) while the primitive's blocking tl.dot serializes one tile DMA and plateaus at ~166 GB/s — a 25-28% latency win that widens with context. This refines the paper's 'decode is latency-neutral' claim: neutral at 64-way production scale (reduce-dominated), but the composite extracts bandwidth at the local level. The bandwidth roofline here mirrors the MAC roofline in prefill.
Adds: gqa_decode_streaming.py sweep (wired into the milestone umbrella as GQA_1H_SWEEPS=decode_streaming), paper_plot_gqa_decode_streaming.py, the figure, and a new fig:gqa-decode-stream + paragraph in 05-gqa.tex; rebuilt main.pdf. Prefill (Experiment B) re-verified byte-identical (794.1/668.1/646.9us).
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
ywkang
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