Two strands bundled as the 1H-codesign-paper refresh unit:
(A) This session — single-op cost-model reflection (depends on 2d8271c):
- §2 Table 2 (tab:hw): split "FIXED per command" into "FIXED per
single-op command" (8 cycles) and "FIXED per composite command"
(40 cycles); §2 dispatch-overhead prose updated to the two-class split.
- §3.4 (sec:gemm-vs-async): rename paragraph headers + prose to
async-full / async-tiled; "atomic" -> "single-op" throughout; reframe
mechanism #3 from the old DMA-only fast-path to the single-op
fast-path. Headline narrative now: even with EVERY single-op cmd
(96 DMA + 48 dot + 47 add) charged the light 8-cycle FIXED, composite
still wins ~2.8x at K=3072 purely on command-count structure (1 vs
192 commands) -- down from the pre-D8 ~6.3x, and explicitly NOT a
modelling artifact. Numbers refreshed from the regenerated sweep:
async-full 3.83->3.91, async-tiled 1.14->~2.53, under-tile corner
1.06->1.21, depth-2 vs depth-inf spread <1%. New figure wired in.
- build/main.pdf rebuilt (tectonic); pdftotext-verified (no broken
refs; Table 2 split, single-op terms, 2.8x/2.53/192-host-commands
all present).
(B) Prior-session paper work riding along uncommitted: §4 all-reduce
deep-edit, §5 GQA, §6 discussion trims; milestone_1h_ccl.py plot
label "FSIM" -> "H2 2025 SW queue baseline"; regenerated diagrams
under docs/diagrams/** and gemm output PNGs under
1H_milestone_output/gemm/. (Composite-window gemm plots are
unaffected by D8 — D8 only changes single-op dispatch FIXED, which
the composite window excludes.)
All TODO items for the D8 single-op extension are now complete and
pushed across 3 commits (2d8271c cost-model+ADR+tests, 821bbf2 bench
harness, this paper refresh). Full regression green (826 passed, 1
skipped). No remaining work.
NOTE for review (carried from 2d8271c): ADR-0065's "2x CPU-offload win"
headline for GQA decode opt2 may want a refresh to the post-D8 ~1.87x.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
§2 platform:
- Add a "memory-centric AHBM" sentence to the device-and-execution
intro: each PE is paired with dedicated HBM bandwidth and on-PE
TCM, so the performance question is about feeding compute from
locally-attached memory + moving the unavoidable inter-PE traffic
efficiently. Makes the AHBM character of the platform visible
before §2.3 starts unpacking the latency model.
- Promote "Congestion and contention modeling" from \paragraph to
\subsubsection: this is the platform's core differentiator over a
peak-BW roofline, so it deserves its own heading.
- Rename "Control-plane (issue) cost model" to "Command dispatch
overhead model" -- describes what it actually charges (the PE_CPU
paying a fixed + per-byte cost to push a command to one of the
accelerator engines) without the more abstract "control-plane"
framing.
- Add a third Accuracy cross-check from kernbench probe: a
PE→HBM DMA-distance sweep that confirms monotonic hop progression,
bandwidth saturation matching the per-edge model, and the built-in
invariants (D2H >= H2D, cross-CUBE best < worst). New
Table~\ref{tab:probe-pe-dma} reports per-traversal latency and
utilisation at 32KiB / 1MiB across five hop classes.
- Captured probe output as figures/probe_pe_dma_summary.txt for
reproducibility.
§5 PE_IPCQ / all-reduce:
- Re-ran milestone-1h-ccl on current sim_engine (post-ADR-0064 Rev2
and the IPCQ slot-wrap Phase-2 race fix). Updated the topology-
comparison table and the buffer-kind caption to the fresh raw
latencies. Headline ratios are preserved:
torus vs mesh saving at 96 KB/PE: 24.8% (was 24.8%) -> ~25%
torus vs ring saving at 96 KB/PE: 19.3% (was 19.3%) -> ~19%
TCM vs HBM saving at 64 KB/PE: 13.4% (was 13.9%) -> ~13%
TCM vs SRAM saving at 64 KB/PE: 37.2% (was 38.3%) -> ~37%
The Executive Summary's "up to ~14%" / "up to ~38%" framing stays
consistent with these post values.
Artifacts refreshed in src/kernbench/benches/1H_milestone_output/:
- ccl/summary.csv + per-topology PNGs + buffer-kind CSV/PNG
- ccl/comparison_mesh_vs_ring_vs_2DTorus_vs_theoretical_vs_fsim.png
- gemm/* (re-run yields identical pe_window structure; PNGs
refreshed)
Paper figures synced to the fresh artifacts:
- figures/allreduce_comparison.png
- figures/allreduce_buffer_kind.png
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
New `/paper` slash-command skill that synthesizes ADR/SPEC content and live
KernBench benchmark results into a sectioned LaTeX technical paper compiled
to PDF with Tectonic (auto-installed). The skill negotiates a TOC, grounds
every number in committed artifacts or fresh bench runs, and keeps
report-only benches isolated.
This commit also includes the first generated report:
- docs/report/1H-codesign-paper/ — main.tex + per-section .tex, figures,
toc.md contract, and the built 8-page main.pdf. Covers the platform
(source-level kernels, latency model + accuracy, HW config from
topology.yaml), GEMM via composite command, All-Reduce via PE_IPCQ, and
fused GQA combining both, plus discussion/conclusion/2H future work.
- scripts/paper/ — isolated report harnesses (not registered benches):
paper_gqa_latency.py harvests per-panel GQA end-to-end latency + engine
occupancy (the milestone only emitted op-counts); paper_plot_gqa.py
renders the GQA figures.
GEMM/All-Reduce reuse committed milestone figures/CSVs; GQA results are
generated fresh. Honest flags retained: PE_CPU dispatch cost is 0 in this
config, and the proposed two-composite softmax_merge decode is marked
designed-not-measured.
Co-Authored-By: Claude Opus 4.8 (1M context) <noreply@anthropic.com>
ywkang
