feat(distributed): add cal_all_to_all_v_blocks launch-width mapping (RFC #2521 K2) - #2743
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Included review availability: Your plan provides up to 2 included reviews per hour; 1 remains after this review. 📝 WalkthroughWalkthroughThe change adds ChangesLaunch-width calculation API
Priority: ⬇️ Low Estimated code review effort: 2 (Simple) | ~10 minutes Change: Feature Merge Risk: 🟡 Moderate · up to The stack still carries unresolved risks that could cause incorrect collective counts or omit required communication handling, so these issues should be resolved before merge. 🚥 Pre-merge checks | ✅ 4 | ❌ 1❌ Failed checks (1 warning)
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Warning Some tools did not complete. Review the errors below. 🔧 Ruff (0.16.5)python/pypto/ir/op/distributed/launch_width.py�[1;31mruff failed�[0m tests/ut/ir/test_distributed_ops.py�[1;31mruff failed�[0m Thanks for using CodeRabbit! It's free for OSS, and your support helps us grow. If you like it, consider giving us a shout-out. A rabbit counts the blocks in line Comment |
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Inline comments:
In
`@python/pypto/runtime/builtins/collectives/all_to_all_v/templates/kernel.cpp.in`:
- Around line 315-320: In the all-to-all kernel’s peer-count handling, snapshot
and clamp each peer’s send count immediately after the start barrier, storing
the results in local storage before the completion barrier. Update the current
recv_counts construction to use those snapshots after the completion barrier
instead of rereading remote_send_slot, while preserving the existing count
bounds.
In `@src/ir/transforms/insert_comm_fence_pass.cpp`:
- Around line 473-478: Update OrchPostCollectiveScanner::ScanStmt for ForStmt
and WhileStmt to rescan each sequential loop body with seen_publish=true when
its initial scan discovers a publish, preserving the existing scan result. Skip
this rescan for ForKind::Parallel loops, and add coverage for a loop-carried
consume-then-collective case.
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docs/en/dev/passes/51-insert_comm_fence.mddocs/en/dev/passes/index.mddocs/zh/dev/passes/51-insert_comm_fence.mddocs/zh/dev/passes/index.mdpython/pypto/ir/op/distributed/__init__.pypython/pypto/ir/op/distributed/launch_width.pypython/pypto/ir/op/distributed/tensor_ops.pypython/pypto/runtime/builtins/collectives/all_to_all_v/templates/kernel.cpp.insrc/ir/transforms/insert_comm_fence_pass.cpptests/ut/ir/test_distributed_ops.pytests/ut/ir/transforms/test_insert_comm_fence.py
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…ts, launch-width Rescan sequential loop/while bodies for loop-carried Phase B order (skip parallel), memoize wrapper resolution, reject non-int cal_all_to_all_v_blocks inputs, and snapshot peer send_counts after the start barrier so Phase 2 recv_counts matches this call's payload.
Review follow-up (
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…ts, launch-width Rescan sequential loop/while bodies for loop-carried Phase B order (skip parallel), memoize wrapper resolution, reject non-int cal_all_to_all_v_blocks inputs, and snapshot peer send_counts after the start barrier so Phase 2 recv_counts matches this call's payload.
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…ts, launch-width Rescan sequential loop/while bodies for loop-carried Phase B order (skip parallel), memoize wrapper resolution, reject non-int cal_all_to_all_v_blocks inputs, and snapshot peer send_counts after the start barrier so Phase 2 recv_counts matches this call's payload.
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…ts, launch-width Rescan sequential loop/while bodies for loop-carried Phase B order (skip parallel), memoize wrapper resolution, reject non-int cal_all_to_all_v_blocks inputs, and snapshot peer send_counts after the start barrier so Phase 2 recv_counts matches this call's payload.
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…RFC hw-native-sys#2521 K2) Frozen contract item 3: a pure (P, L) -> B admission mapping — the admitted block count for all_to_all_v — with no payload input. Computed once and never recomputed downstream (contract item 11). B = L if L < P (each block owns multiple peers) B = (L // P) * P if L >= P (highest multiple of P that is <= L) `core_num` is a requested maximum L, not a promise to launch exactly L. - python/pypto/ir/op/distributed/launch_width.py (new): cal_all_to_all_v_blocks, rejecting non-int (bool/float) arguments, non-positive P and non-positive L. - python/pypto/ir/op/distributed/__init__.py: export the helper. - tests/ut/ir/test_distributed_ops.py: the RFC's own 8-row worked-example table, 4 non-positive cases, 4 non-integer cases. Standalone infrastructure with no callers yet. The eventual runtime call site is entry.cpp.in, a self-contained template with no link-time dependency on these compiler sources, so it carries its own C++ mirror of this formula in the follow-up PR in this stack rather than linking against this module. Review follow-up: the module docstring now anchors the call-site explanation to RFC hw-native-sys#2521 instead of naming an out-of-tree planning document, and the Raises section states explicitly that int subclasses are rejected along with bool and float.
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On the ticket-compliance analysisThanks — two of the "requires further human verification" items are real design questions worth 1. What keeps the Python reference and the C++ mirror in sync?Straight answer: there is no automated numerical-equivalence check between them, and there cannot What exists instead is three levels of pinning, none of which is a proof:
So a rewrite of either formula fails a test. Residual risk, stated plainly: the C++-side check is a text assertion, not an evaluation, and it 2. Does the RFC's table match the eight worked examples?Yes — row for row, in the same order.
The RFC's launch-width policy table is consistent with it as well: its 3. What the non-compliant list is really measuringThe list is an accurate description of RFC #2521 as a whole. This PR is one step of a four-branch
The three sibling branches are pushed, but this is the only one of the four with a PR open; the later 4. Exact-traffic looks already done
Two RFC passages may simply be stale rather than unmet, and I flag them as observations, not 5. Review threadsAll five threads are resolved. Four are 6. Current head, and the stack's headsThe branch head is now For anyone following the stack: all four branches were re-cascaded onto the corrected 117 and
Baseline: unmodified
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✅ Action performedReview finished.
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Closing in favour of #2889 |
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Summary
Implements RFC #2521 work item K2's
CalAllToAllVBlocks(P, L)— the pureL -> Blaunch-width mapping that frozen contract item 3specifies. Standalone infrastructure: it makes no behaviour change to any existing code, and
nothing calls it yet.
Plan 117 of the K2 stack (117 -> 118 -> 119 -> 120).
The contract
core_numis a requested maximumL, not a promise to launch exactlyL. The admittedblock count is:
Bis computed once and never recomputed downstream (frozen contract item 11), and takes nopayload input — so shapes and
valid_elemsnever influence it.Changes
python/pypto/ir/op/distributed/launch_width.py(new) —cal_all_to_all_v_blocks(p, l).Rejects non-
intarguments (booland floats, so the annotatedintcontract holds),non-positive
P, and non-positiveL.python/pypto/ir/op/distributed/__init__.py— exports the helper.tests/ut/ir/test_distributed_ops.py— the RFC's own 8-row worked-example table plus4 non-positive and 4 non-integer rejection cases (16 tests).
No C++/bindings/
.pyichanges: the eventual runtime call site isentry.cpp.in, aself-contained template with no link-time path back into these compiler sources, so it carries
its own C++ mirror of the formula (plan 120) rather than linking against this module.
What this PR is not
core_numstays a compile-time-only kwarg until plan 118makes it a genuine dynamic argument.
Verification
Sim Docker
pypto3-hw-native-sys:sim, rebuilt 2026-09-22 fromDockerfile.hw-native-sys.sim.ubuntu22.04(PYPTO_COMMIT=d626aea16, PTOAS v0.65); worktreemounted and installed with
pip install --no-build-isolation -e ..tests/ut/ir/test_distributed_ops.py(the touched file)tests/utat this head73098c98btests/uton unmodifiedmaind626aea16, same imageThe delta is exactly +16 passed — this PR's own tests. Nothing else moved. The baseline was
re-measured rather than reused, because
maingained two commits (below) since the previousrevision was verified.
The single failure is pre-existing and environment-caused, not a regression:
tests/ut/language/test_unified_ops.py::TestUnifiedSlicePadValue::test_symlinked_import_path_still_names_the_callerreproduces identically on unmodified
mainin the same image (an editable-install symlink-pathnaming issue).
Revision history
The original revision was cut from K1's
feat/all-to-all-v-flat-tput, so its diff carried all ofK1's commits (17 files / +739/-190) and went
CONFLICTINGasmainmoved. It was rebuiltdirectly on
main: this PR's own content — the mapping, its export, and its tests — isbyte-for-byte unchanged, and the K1 content is no longer part of it. Same code, 3 files.
2026-09-22 re-cascade. K1 merged (
#2828->mainas5cb75663a), andmainalso gained#2837(the PTOAS v0.65 bump), movingmaintod626aea16. This branch was rebuilt onto itwith zero conflicts and re-verified end to end on a freshly built image — the counts above are
from that run, not the earlier one.
What is next in the K2 stack
Three more PRs on top of this one, all now re-cascaded onto the merged
maind626aea16:feat/all-to-all-v-core-num-argeec7d51bfcore_numas a genuine dynamic argfeat/all-to-all-v-noop-clamp-barrier57db5634a[NR, S]signal + block-aware barrierfeat/all-to-all-v-multiblock-enable4e08ea8b2B>1on the HOST rail118 and 119 depend on this PR's helper; 120 is where
CalAllToAllVBlocksfinally gets called.