h3-blackwell-runtime/research/vortex_exact_attention/EXPERIMENT_LOG.md

# Experiment Log

This is append-only. Projected ranges are design estimates, never achieved
results.

## 2026-08-26: Phase 0 Import And Verification

Status: `research_retained`

Hypothesis: the retained Sage inventory is sufficient to import the exact
observable contract without repeating prior experiments.

Actions:

- Verified public SageAttention commit
  `d1a57a546c3d395b1ffcbeecc66d81db76f3b4b5` exists.
- Rehashed ten retained contract, parity, timing, and NCU artifacts; all matched
  `benchmarks/reference_inventory.json`.
- Imported Q/K preparation, K smoothing, INT8 quantization, QK traversal,
  online-softmax, FP8 V/P, two-level PV accumulation, final conversion, and
  ragged-tail contracts into `NUMERICAL_CONTRACT.md`.
- Recorded missing production binary/checkpoint hashes and missing standalone
  canonical input tensors as blockers rather than fabricating provenance.
- Did not execute inference, modify dispatch, or touch the production service.

Decision: Phase 0 is verified as an imported specification. No kernel work is
authorized until Phase 1 selects a structural state-ownership architecture.

## Closed Prior Work

| Work | Result | Preservation / reopening rule |
| --- | --- | --- |
| P0 register caps | Three-CTA threshold at 168 registers caused catastrophic spills; no gain | Timing/JSON/NCU retained; exact candidate source missing and must not be claimed reproducible |
| P0 scope/lifetime narrowing | Fewer spills, approximately `0.06%` gain | Reopen only with structural ownership change |
| P0 score aliasing | Approximately `0.01%`, noise | Do not repeat unchanged |
| P0 early K prefetch | Approximately `0.30%` slower | Reopen only with a different producer/consumer pipeline |
| P0 softmax interleaving | Neutral/slower | Do not repeat unchanged |
| P0 padded V shared memory | Same excessive wavefronts, no gain | Reopen only if staging instructions/dataflow change |
| P1 entry fusion | `20.9-23.4%` isolated; only `0.535-0.863%` complete-block | Reuse partial implementation only inside an owned attention pipeline |
| P2 direct V preparation | `39.48%`, `4.17 ms`; only `0.909%` of block | Reuse partial implementation only inside an owned attention pipeline |
| P3 temporal pairing | Exact/sanitizer-clean; approximately `0.10%`; private state remained live | Complete patch and launcher retained; new work must transfer/partition ownership |
| Hopper WGMMA retarget | CUDA 13 rejects WGMMA for `sm_121a` | Reopen only with changed ISA/toolchain support |
| SM121 UMMA INT8 QK | Public SM120/121 Blackwell MMA path does not expose a Sage-compatible UMMA INT8 operation | Retain supported INT8 `mma.sync` unless capability changes |

P1/P2 source is partial and mixed in
`research/shared_cuda_experimental_worktree/`. P3 source and launcher are
complete under `research/sage2_temporal_pair/`. Exact P0 variant patches are
unrecoverable; historical commands and environments must not be invented.

## 2026-08-26: Phase 1 State-Ownership Decision

Status: `research_retained`

Evaluated three architectures that permanently separate QK/softmax state from
PV/output state: VEA-A Q64 split-D intra-CTA, VEA-B Q128 paired owners, and
VEA-C two-CTA DSM ownership split. All retain strict tile order, exact FP8 score
bytes, per-tile RO rescaling, two-level PV accumulation, and final conversion.

Decision: recommend VEA-B after register/shared/barrier/dual-pipe capability
probes. Its projected `180-207 ms` mainloop screening range has a credible sub-190 path
without depending on unverified DSM. VEA-A is the fallback; VEA-C is conditional
on cluster residency and DSM latency. These are projections only.

No kernel was implemented, no inference was run, and production dispatch and
services were not modified.

Phase commits:

- Phase 0 contract import: `c502842`
- Phase 1 architecture decision: `b842bad`