fix: build against rmm 26.10 (use rmm's device_uvector declaration)

[maxwbuckley]

Description

Building libcuopt from source against rmm 26.10 fails to compile because cpp/src/pdlp/utilities/problem_checking.cuh hand-rolls a forward declaration of rmm::device_uvector in the plain rmm namespace:

namespace rmm {
template <typename T>
class device_uvector;
}  // namespace rmm

rmm 26.10 places device_uvector in an ABI inline namespace (rmm::RMM_ABI_NAMESPACE, see rmm/detail/export.hpp), so this hand-rolled declaration creates a second, distinct rmm::device_uvector. Every use then becomes ambiguous:

cpp/src/pdlp/utilities/problem_checking.cuh(36): error: "rmm::device_uvector" is ambiguous
cpp/src/utilities/copy_helpers.hpp(82): error: "rmm::device_uvector" is ambiguous

with cascading namespace "cuopt::raft" has no member "add_op" and thrust "this pragma must immediately precede a declaration" errors in the same translation units.

This is the only manual rmm forward declaration in the tree. cuOpt already opts out of thrust's and cub's ABI namespaces (-DTHRUST_DISABLE_ABI_NAMESPACE / -DCUB_DISABLE_NAMESPACE_MAGIC); rmm's ABI inline namespace is newer and has no such opt-out, so the plain forward declaration no longer matches rmm's real declaration.

Change

Replace the hand-rolled forward declaration with #include <rmm/device_uvector.hpp>, so rmm's own (correctly ABI-namespaced) declaration is used.

Testing

Built libcuopt (LP + MIP) from source against rmm/raft 26.10 + CCCL 3.4.0 (CUDA 13.3, GCC 14, sm_120a):

• Before: the device_uvector is ambiguous errors above.
• After: clean compile + link. solve_LP returns correct optima — afiro → -464.7531 (known optimum), and a set of small LPs match HiGHS to ≤ 1e-6 relative error — and the MIP path runs.

Fixes #1605.

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ℹ️ Recent review info

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Run ID: 60622ac7-f581-4340-8601-7e905461832b

📥 Commits

Reviewing files that changed from the base of the PR and between d47fcd6 and 2ca07f2.

📒 Files selected for processing (1)

• cpp/src/pdlp/utilities/problem_checking.cuh

🚧 Files skipped from review as they are similar to previous changes (1)

• cpp/src/pdlp/utilities/problem_checking.cuh

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📝 Walkthrough

Walkthrough

The problem-checking header now includes RMM’s official device_uvector declaration instead of defining a manual forward declaration.

Changes

RMM declaration alignment

Layer / File(s)	Summary
Use the official RMM header cpp/src/pdlp/utilities/problem_checking.cuh	Replaces the hand-rolled rmm::device_uvector forward declaration with rmm/device_uvector.hpp.

Estimated code review effort: 1 (Trivial) | ~2 minutes

Suggested reviewers: mlubin, yuwenchen95

🚥 Pre-merge checks | ✅ 5

✅ Passed checks (5 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly states the main fix: using rmm's device_uvector declaration for rmm 26.10.
Description check	✅ Passed	The description directly matches the code change and the reported build failure against rmm 26.10.
Linked Issues check	✅ Passed	The change satisfies #1605 by replacing the manual forward declaration with the official rmm header.
Out of Scope Changes check	✅ Passed	The PR is narrowly scoped to the rmm device_uvector declaration fix and adds no unrelated changes.
Docstring Coverage	✅ Passed	No functions found in the changed files to evaluate docstring coverage. Skipping docstring coverage check.

✨ Finishing Touches

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• Create PR with unit tests

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