Both mesh kernels and the milestone-gqa bench described single_user vs
multi_user in ways that were architecturally misleading. Source of truth
is the GQA Llama-70B sharding study at
llm_paper_review/notes/GQA_MHA_sharding/scripts/_gen_llama70b_1M_4cases.py:
Single User (B=1) — TL prefill, BL decode:
KV split @ PEs intra-cube. Each cube does its own 8-PE ring,
independent of other cubes. Headline = 64 cubes serving one user.
Multi User (B=8) — TR prefill, BR decode:
KV split @ cubes inter-cube. 8 cubes/KV-group form the ring; inside
each cube, "8 PEs each handle 1 different user → Batch on batch."
Updates the rank_axis docstring on both mesh kernels and the bench's
module docstring to make this accurate, including the v1 simplification
of the multi_user kernel (gating pe_id != 0 collapses B=8 → B=1; the
per-cube batch parallelism is deferred to sub-cycle 4c headline).
No behavior change; existing tests unchanged.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
ADR-0059 single_user_* panels run the ring across PEs in one cube
(rank == tl.program_id(axis=0)). multi_user_* panels run the ring
across cubes — rank should be cube_id (axis=1), and 7 of every 8 PEs
in each cube must stay silent because the cube-level SFR install only
gives the cube-coordinate PE 0 an E/W neighbor.
Add ``rank_axis: int = 0`` kwarg to both ``attention_mesh_mlo_kernel``
and ``attention_mesh_kv_kernel``:
- 0 (default): rank == tl.program_id(axis=0). Existing single_user
behavior, all spec tests unchanged.
- 1: gate ``if tl.program_id(axis=0) != 0: return`` at kernel start,
then ``rank = tl.program_id(axis=1)``. multi_user_* panels pass
this to the kernel via ctx.launch positional arg.
Also brings in _attention_mesh_kv.py and _attention_mesh_mlo.py as
the committed home of the ADR-0059 kernels (previously living
uncommitted in the working tree from sub-cycle 4b).
Tests: 7-test rank_axis spec file (default-path + rank_axis=1 gating
and cube-id semantics, both kernels); 4-panel diag harness now green
end-to-end (single_user_prefill/decode + multi_user_prefill/decode);
763-test wider sweep clean.
Co-Authored-By: Claude Opus 4.7 (1M context) <noreply@anthropic.com>
mukesh