refactor: replace rmm::device_scalar with cudf::detail::device_scalar - #23618
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vyasr wants to merge 2 commits into
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refactor: replace rmm::device_scalar with cudf::detail::device_scalar#23618vyasr wants to merge 2 commits into
vyasr wants to merge 2 commits into
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Introduce a self-contained cudf::detail::device_scalar<T> wrapper (size-1 rmm::device_uvector storage) and migrate all libcudf source, tests, and libcudf_streaming to use it. Updates the scalar hierarchy ctor signatures from rmm::device_scalar<T> to cudf::detail::device_scalar<T> (public API change), refreshes DEVELOPER_GUIDE.md guidance. This completes plan drop-rmm-device-scalar.md. A follow-up change removes the final rmm::device_scalar usage in compute_single_pass_aggs.cuh.
Replace the exemption rmm::device_scalar<cuda::std::atomic_flag> in compute_single_pass_aggs.cuh with rmm::device_uvector<cuda::std::atomic_flag> of size 1 — semantically identical (device_scalar is a size-1 device_uvector under the hood) but eliminates the last direct rmm::device_scalar reference from libcudf source. atomic_flag cannot use cudf::detail::device_scalar because it is not trivially copyable, but device_uvector has no such requirement. Completes plan drop-final-rmm-device-scalar-usage.md.
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bdice
reviewed
Aug 11, 2026
| [[nodiscard]] T const* data() const noexcept { return _storage.data(); } | ||
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| rmm::device_uvector<T> _storage; |
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Should we just go straight to cuda::buffer here?
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I chose not to, I'd prefer to do all the cuda::buffer switches concurrently so that reviewers can see the type in action in multiple places at once for comparison.
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Description
Replaces libcudf's direct
rmm::device_scalarusage withcudf::detail::device_scalar, which now owns size-1rmm::device_uvectorstorage directly. Also removes the finalrmm::device_scalar<cuda::std::atomic_flag>use in groupby hash aggregation by using a size-1rmm::device_uvectorinstead. The developer guide is updated accordingly.Checklist