[STF] Locality-domain tests: single-domain devices have nothing to split by caugonnet · Pull Request #11994 · NVIDIA/cccl

caugonnet · 2026-10-13T10:24:56Z

Description

Fixes the two locality-domain test failures seen in #11991 (forward-compat cuda-compat-13-4 user-mode driver over an R595 kernel driver, single H100 PCIe):

locality_domain_alloc.cu(84): -1 == 0 is false
locality_domain_split_method.cu(153): 2 == 0 is false

Neither is a driver-version problem the existing waiver (#11837) can catch: under forward compat cuDriverGetVersion reports 13.4. Both are the tests over-specifying what a single-domain device must return:

The driver documents that a localized allocation on domain 0 of a single-domain device is a plain device allocation, so the pointer ordinal is -1.
Asking the driver to split SMs by domain on a one-domain device is pointless, and a user-mode driver without real locality-domain support hands back an unsplit device (114 SMs vs. an alignment of 8) without reporting an error.

Checklist

New or existing tests cover these changes.
The documentation is up to date with these changes.

🤖 Generated with Claude Code

On a device reporting a single locality domain the domain is the device: the driver documents that a localized allocation on domain 0 is a plain device allocation (ordinal -1), and asking it to split SMs by domain is pointless at best. A forward-compat user-mode driver on an older kernel driver (CI VMs with cuda-compat-13-4 over R595) goes further and hands back an unsplit device without reporting any error, which the structural checks of locality_domain_split_method then trip over (114 SMs against an alignment of 8), while locality_domain_alloc expected ordinal 0. - Extend the whole-device degrade of the native backend to single-domain devices: every split method maps to the one whole-device green context, exactly like the "driver cannot answer" case. No new driver check. - locality_domain_split_method: read each place's SM partition through the public API (activate the place, query the current context) instead of reaching into locality_domain_ctx_cache / native_raw_count. With several domains, assert that every group echoes the requested domain in its flags/localityDomainId before checking the structural properties, so an unhonored split fails loudly instead of being ignored. With one domain, assert the documented degenerate answers (equal places, whole device). Branch on locality_domain_count instead of internals, and on the environment variable for the fake topology. - locality_domain_alloc: accept ordinal -1 on single-domain devices. - Document that the split method is ignored on single-domain devices. Co-Authored-By: Claude Fable 5.1 <noreply@anthropic.com>

copy-pr-bot · 2026-10-13T10:25:00Z

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caugonnet · 2026-10-13T10:28:26Z

/ok to test 3d72e6d

coderabbitai · 2026-10-13T10:34:45Z

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📝 Summary

Summary by CodeRabbit

Bug Fixes
- On devices with a single locality domain, execution now uses the full device’s SM resources, and split-method differences are ignored.
Documentation
- Clarified how split methods behave on single-domain devices and how execution places compare on multi-domain devices.

On native CUDA, devices with one locality domain now use a whole-device context regardless of the requested split method. Tests validate execution-place identity, SM partitions, and allocation ordinals for single- and multi-domain cases.

Changes: Locality-domain execution

Layer / File(s)	Summary
Canonicalize single-domain execution places `cudax/include/cuda/experimental/__places/exec/locality_domain.cuh`, `docs/cudax/places.rst`	The cache uses the backfill split when the native domain count is at most one. The sole domain receives the full SM resource. Documentation describes how split methods behave on single- and multi-domain devices.
Validate locality places `cudax/test/stf/places/locality_domain_split_method.cu`, `cudax/test/stf/places/locality_domain_alloc.cu`	Tests use activated execution places to check single- and multi-domain SM partitions. Allocation checks expect ordinal `-1` for single-domain devices.

Priority: ⬇️ Low

Change: Bug fix

Merge Risk: 🔵 Low · up to 3d72e

Multi-domain fake topology is described inaccurately, and setting its override to zero can produce a false test failure or skip native partition checks. These bounded issues warrant correction but do not otherwise block merging.

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📒 Files selected for processing (4)

cudax/include/cuda/experimental/__places/exec/locality_domain.cuh
cudax/test/stf/places/locality_domain_alloc.cu
cudax/test/stf/places/locality_domain_split_method.cu
docs/cudax/places.rst

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coderabbitai · 2026-10-13T10:34:48Z

      &ordinal, CU_POINTER_ATTRIBUTE_LOCALITY_DOMAIN_ORDINAL, reinterpret_cast<CUdeviceptr>(ptr)));
    if (std::getenv("CUDASTF_DISABLE_LOCALIZED_MEMORY") != nullptr
-        || std::getenv("CUDASTF_FAKE_LOCALITY_DOMAINS") != nullptr)
+        || std::getenv("CUDASTF_FAKE_LOCALITY_DOMAINS") != nullptr || ndomains == 1)


🎯 Functional Correctness | 🟡 Minor | ⚡ Quick win

suggestion: Test the parsed fake-topology state in both files. locality_domain_fake_count() disables the override for 0 and non-numeric values. Environment-variable presence therefore does not establish that fake topology is active.

cudax/test/stf/places/locality_domain_alloc.cu#L80-L80: use the parsed count so a native multi-domain allocation is not incorrectly expected to report -1.

cudax/test/stf/places/locality_domain_split_method.cu#L94-L94: use the parsed count so native partition checks are not incorrectly waived.

📍 Affects 2 files

cudax/test/stf/places/locality_domain_alloc.cu#L80-L80 (this comment)

cudax/test/stf/places/locality_domain_split_method.cu#L94-L94

coderabbitai · 2026-10-13T10:34:48Z

+the fake-topology override) accept and ignore the method: the domain is the
+device.


🎯 Functional Correctness | 🟡 Minor | ⚡ Quick win

suggestion: Limit “the domain is the device” to whole-device cases. With CUDASTF_FAKE_LOCALITY_DOMAINS=N and N > 1, each fake domain is a green-context SM partition. The override ignores the split method, but a fake domain is not the whole device. Separate that case from the whole-device cases. As per path instructions, documentation changes require “technical accuracy” and “API/version consistency.”

Source: Path instructions

wmaxey · 2026-10-14T16:40:42Z

/ok to test 8dd4346

pciolkosz · 2026-10-15T00:43:32Z

/ok to test 0cb1ede

copy-pr-bot · 2026-10-15T00:43:35Z

/ok to test 0cb1ede

@pciolkosz, there was an error processing your request: E2

See the following link for more information: https://docs.gha-runners.nvidia.com/cpr/e/2/

pciolkosz · 2026-10-15T00:45:27Z

/ok to test 0cb1ede

copy-pr-bot · 2026-10-15T00:45:30Z

/ok to test 0cb1ede

@pciolkosz, there was an error processing your request: E2

See the following link for more information: https://docs.gha-runners.nvidia.com/cpr/e/2/

pciolkosz · 2026-10-15T00:47:21Z

/ok to test 0cb1ede

github-actions · 2026-10-15T02:20:47Z

🥳 CI Workflow Results

🟩 Finished in 1h 28m: Pass: 100%/73 | Total: 15h 15m | Max: 1h 08m | Hits: 100%/45918

See results here.

AI failure analysis

1. MatX SAR backprojection conversion rejected as an error · 1 job

Explanation: MatX commit 424f0df72670804024b533787d6c70c146e27b14 passes a potentially wider expression to the float-only `__sincosf` intrinsic, and NVCC 13.4 promotes the conversion warning because MatX enables `-Wconversion -Werror`. The PR changes only CUDA Experimental locality-domain files, so the evidence does not connect this third-party source error to the PR.

Evidence:

2026-10-15T00:57:04.5343956Z /home/coder/cccl/build/cuda13.4ext-gcc14/matx/MatX/include/matx/kernels/sar_bp.cuh(777): error #2463-D: conversion may change the value
2026-10-15T00:57:04.5344993Z    __sincosf(phase_correction_partial * w, &incr_sinx, &incr_cosx);
2026-10-15T00:59:25.7549826Z /home/coder/cccl/build/cuda13.4ext-gcc14/matx/MatX/include/matx/kernels/sar_bp.cuh(777): error #2463-D: conversion may change the value

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Repository: https://github.com/NVIDIA/cccl
Workflow run: https://github.com/NVIDIA/cccl/actions/runs/38662021876
Failure group: MatX SAR backprojection conversion rejected as an error
Affected jobs:
- Build MatX (optional) / Build MatX: https://github.com/NVIDIA/cccl/actions/runs/38662021876/job/116185409247

Reproduce narrowly by compiling MatX's SAR backprojection example and test at MatX commit 424f0df72670804024b533787d6c70c146e27b14 with CUDA 13.4 and GCC 14 against both the PR and its base revision. If float precision is intentional, patch `include/matx/kernels/sar_bp.cuh` to explicitly convert the first `__sincosf` argument to float; otherwise select the precision-appropriate sine/cosine intrinsic. Verify the SAR example, benchmark, and test objects compile without globally disabling conversion diagnostics. If the base revision also fails and MatX cannot be patched here, pin the integration to a compatible MatX revision or add a narrowly scoped temporary workaround.

Jobs:

Build MatX (optional) / Build MatX

2. cuOpt uses RMM stream APIs absent from librmm 26.12 · 1 job

Explanation: cuOpt main commit 729b27a4bce83046d5626901ee1ca84013cad210 is compiled against the 26.12 nightly RMM package, but numerous cuOpt translation units call the missing `cuda_stream::view()` API; another object reports that `rmm::cuda_stream_default` is missing. This indicates cuOpt/RMM API-version skew, with no evidence that the locality-domain PR caused it.

Evidence:

2026-10-15T00:56:10.3215797Z /home/coder/cuopt/cpp/src/pdlp/distributed_pdlp/multi_gpu_engine.cu(283): error: class "rmm::_RMM_26_12::cuda_stream" has no member "view"
2026-10-15T00:54:46.2988140Z warning  libmamba [librmm-26.12.00a25-cuda13_261014235638_466b313a] The following files were already present in the environment:
2026-10-15T00:56:34.3528534Z ninja: build stopped: subcommand failed.

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Repository: https://github.com/NVIDIA/cccl
Workflow run: https://github.com/NVIDIA/cccl/actions/runs/38662021876
Failure group: cuOpt uses RMM stream APIs absent from librmm 26.12
Affected jobs:
- Build RAPIDS (optional) / cuopt: https://github.com/NVIDIA/cccl/actions/runs/38662021876/job/116185435147

Reproduce the cuOpt compilation with cuOpt commit 729b27a4bce83046d5626901ee1ca84013cad210 and `librmm-26.12.00a25`, comparing the PR with its base revision. Inspect the installed RMM stream headers and update cuOpt to the current API: replace `.view()` with the supported direct conversion or explicit `cuda_stream_view` construction, and replace `rmm::cuda_stream_default` with the current default-stream facility. If external cuOpt cannot be patched here, pin the RAPIDS job to mutually compatible cuOpt and RMM revisions instead of combining cuOpt main with an incompatible nightly package. Validate by compiling the previously failing PDLP, feasibility-jump, shard, and gRPC objects, then rerun only the focused cuOpt job.

Jobs:

Build RAPIDS (optional) / cuopt

caugonnet requested review from a team as code owners October 13, 2026 10:24

caugonnet requested a review from gonidelis October 13, 2026 10:24

github-project-automation Bot added this to CCCL Oct 13, 2026

caugonnet requested a review from andralex October 13, 2026 10:25

github-project-automation Bot moved this to Todo in CCCL Oct 13, 2026

cccl-authenticator-app Bot moved this from Todo to In Review in CCCL Oct 13, 2026

Merge branch 'main' into stf/locality-domain-tests-single-domain

3d72e6d

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Merge branch 'main' into stf/locality-domain-tests-single-domain

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pciolkosz added 2 commits October 14, 2026 13:20

Merge branch 'main' into stf/locality-domain-tests-single-domain

9905a71

Merge branch 'main' into stf/locality-domain-tests-single-domain

0cb1ede

Jacobfaib approved these changes Oct 15, 2026

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caugonnet merged commit 8406f5a into NVIDIA:main Oct 15, 2026
100 of 102 checks passed

github-project-automation Bot moved this from In Review to Done in CCCL Oct 15, 2026

		the fake-topology override) accept and ignore the method: the domain is the
		device.

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