fix(client): hold the GPU variant alternatives behind an opaque pointer by ramakrishnap-nv · Pull Request #1940 · NVIDIA/cuopt

ramakrishnap-nv · 2026-09-18T17:38:46Z

libcuopt_client.so carried an undefined rmm::device_buffer::~device_buffer() and a DT_NEEDED on librmm for a branch it can never take: two client translation units assign to linear_programming_ret_t and mip_ret_t, and a std::variant destructor has to handle every alternative, so both paid for the GPU one despite only ever producing the CPU alternative.

The GPU alternatives are now opaque types held through a unique_ptr whose deleter is a function pointer carried in the object, so a CPU-only translation unit destroys the variant without naming a symbol — needing neither rmm nor an edge to cuopt_mathopt.

Two notes against the issue: symbol 1 was already gone, and its suggested CPU-only return type is blocked by to_python_lp_ret() being virtual over the shared struct.

Closes #1890

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📝 Walkthrough

Walkthrough

Changes

GPU solution results now use opaque pointer holders with callback deleters. PDLP conversion, stream handling, Python bindings, build targets, and symbol checks use the new model. cuopt_client no longer links RMM directly.

GPU solution ownership

Layer / File(s)	Summary
Opaque GPU solution types `cpp/include/cuopt/mathematical_optimization/utilities/cython_types.hpp`, `cpp/include/cuopt/mathematical_optimization/utilities/cython_types_gpu.hpp`	The interface defines forward-declared LP and MIP GPU types with callback-based deleters. GPU-specific definitions retain RMM-backed storage.
GPU conversion and access `cpp/src/pdlp/solution_conversion.cu`, `cpp/src/pdlp/utilities/cython_solve.cu`, `python/cuopt/cuopt/linear_programming/solver/solver.pxd`, `cpp/include/cuopt/mathematical_optimization/optimization_problem_solution.hpp`, `cpp/include/cuopt/mathematical_optimization/optimization_problem_solution_interface.hpp`	PDLP conversion creates the new pointer holders. Stream reassociation and Cython helpers access the wrapped GPU solutions. Documentation describes the new result alternatives.
Leaf linking and validation `cpp/CMakeLists.txt`, `python/cuopt/cuopt/grpc/client/CMakeLists.txt`, `ci/check_symbols.sh`, `conda/recipes/libcuopt/recipe.yaml`	`cuopt_client` no longer links RMM directly. The Cython extension links RMM explicitly. Symbol checks enforce leaf-library constraints.

Priority: ➖ Normal

Estimated code review effort: 3 (Moderate) | ~25 minutes

Change: Bug fix · Severity of issue fixed: Medium

🚥 Pre-merge checks | ✅ 4 | ❌ 1

❌ Failed checks (1 warning)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 25.00% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 12 functions across 7 files. (2 skipped: …	Write docstrings for the functions missing them to satisfy the coverage threshold.

✅ Passed checks (4 passed)

Check name	Status	Explanation
Title check	✅ Passed	The title clearly and concisely describes the main change: GPU variant alternatives are held behind opaque pointers in the client.
Description check	✅ Passed	The description directly explains the client dependency issue, the opaque-pointer solution, and the intended removal of unnecessary GPU-related dependencies.
Linked Issues check	✅ Passed	Issue `#1890` requires `libcuopt_client.so` to have no undefined `rmm`, `raft`, or CUDA symbols, no GPU-stack `DT_NEEDED` entries, and no dependency on another cuOpt library. The client return types now…
Out of Scope Changes check	✅ Passed	The changed C++ types, GPU factories, Cython extraction, link configuration, symbol validation, recipe update, and documentation all support Issue `#1890`. These changes preserve GPU result ownership wh…

Full details: Docstring Coverage

Explanation

Docstring coverage is 25.00% which is insufficient. The required threshold is 80.00%. Docstring coverage is scoped to functions touched by this diff. Analyzed 12 functions across 7 files. (2 skipped: 2 unsupported.)

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Actionable comments posted: 2

🧹 Nitpick comments (1)

cpp/include/cuopt/mathematical_optimization/utilities/cython_types.hpp (1)
45-46: 📐 Maintainability & Code Quality | 🔵 Trivial | ⚡ Quick win

Add Doxygen documentation for the new public GPU holder API.

cpp/include/cuopt/mathematical_optimization/utilities/cython_types.hpp#L45-L46: document the deleter’s ownership contract, null state, and thread-safety.

cpp/include/cuopt/mathematical_optimization/utilities/cython_types_gpu.hpp#L27-L59: document the storage types, deleters, factories, ownership transfer, and GPU requirements.

As per path instructions, “New public functions/classes need Doxygen-style documentation.”
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In `@cpp/include/cuopt/mathematical_optimization/utilities/cython_types.hpp`
around lines 45 - 46,
cpp/include/cuopt/mathematical_optimization/utilities/cython_types.hpp lines
45-46: Add Doxygen documentation to gpu_holder_deleter_t describing its
ownership contract, null state, and thread-safety.
cpp/include/cuopt/mathematical_optimization/utilities/cython_types_gpu.hpp lines
27-59: Add Doxygen documentation for the public storage types, deleters, factory
functions, ownership transfer behavior, and GPU requirements.
Source: Path instructions

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Inline comments:
In `@cpp/CMakeLists.txt`:
- Around line 839-843: Extend the binary validation around ci/check_symbols.sh
to inspect libcuopt_client.so’s undefined symbols and DT_NEEDED entries, rather
than excluding undefined symbols. Fail the check when it detects rmm, raft,
CUDA, librmm.so, or any other cuOpt library dependency, and ensure the
validation runs for libcuopt_client.so.

In `@cpp/include/cuopt/mathematical_optimization/utilities/cython_types_gpu.hpp`:
- Line 19: Add the standard <utility> header alongside the existing includes in
the header containing the std::move calls, so those uses are declared directly
rather than relying on transitive includes.

---

Nitpick comments:
In `@cpp/include/cuopt/mathematical_optimization/utilities/cython_types.hpp`:
- Around line 45-46:
cpp/include/cuopt/mathematical_optimization/utilities/cython_types.hpp lines
45-46: Add Doxygen documentation to gpu_holder_deleter_t describing its
ownership contract, null state, and thread-safety.
cpp/include/cuopt/mathematical_optimization/utilities/cython_types_gpu.hpp lines
27-59: Add Doxygen documentation for the public storage types, deleters, factory
functions, ownership transfer behavior, and GPU requirements.

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📒 Files selected for processing (7)

cpp/CMakeLists.txt
cpp/include/cuopt/mathematical_optimization/utilities/cython_types.hpp
cpp/include/cuopt/mathematical_optimization/utilities/cython_types_gpu.hpp
cpp/src/pdlp/solution_conversion.cu
cpp/src/pdlp/utilities/cython_solve.cu
python/cuopt/cuopt/grpc/client/CMakeLists.txt
python/cuopt/cuopt/linear_programming/solver/solver.pxd

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github-actions · 2026-09-18T19:19:36Z

CI Test Summary

✅ All 32 test job(s) passed.

ramakrishnap-nv · 2026-09-18T19:30:23Z

/ok to test e5c0081

ramakrishnap-nv · 2026-09-18T19:49:13Z

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Inline comments:
In `@ci/check_symbols.sh`:
- Around line 153-163: Expand the undefined-symbol grep expression in the
--require-leaf validation to match symbols beginning with __cuda, while
preserving the existing rmm, raft, cuda, and cu patterns. Expand the DT_NEEDED
expression to also match libnvrtc and libnvJitLink so these CUDA dependencies
are rejected.

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ci/check_symbols.sh
conda/recipes/libcuopt/recipe.yaml
cpp/CMakeLists.txt
cpp/include/cuopt/mathematical_optimization/utilities/cython_types.hpp
cpp/include/cuopt/mathematical_optimization/utilities/cython_types_gpu.hpp
cpp/src/pdlp/solution_conversion.cu
cpp/src/pdlp/utilities/cython_solve.cu
python/cuopt/cuopt/grpc/client/CMakeLists.txt
python/cuopt/cuopt/linear_programming/solver/solver.pxd

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libcuopt_client.so carried an undefined rmm::device_buffer::~device_buffer() and a DT_NEEDED on librmm for a branch it can never take. Two client translation units assign to linear_programming_ret_t and mip_ret_t, and a std::variant destructor has to handle every alternative, so both paid for the GPU one despite only ever producing the CPU alternative. The GPU alternatives are now opaque types held through a unique_ptr whose deleter is a function pointer carried in the object, so a CPU-only translation unit destroying the variant calls through that pointer instead of naming a symbol. It therefore needs neither rmm nor an edge to cuopt_mathopt, which naming the deleter would have created. Definitions live in cython_types_gpu.hpp, included only where CUDA is available. Symbol 1 in the issue, cuda_stream_view's constructor, was already gone. The issue's suggested CPU-only return type is harder than it reads: to_python_lp_ret() is virtual and returns the shared struct, binding the GPU and CPU solution classes to one signature. This leaves it alone. The gRPC Cython extension now links rmm itself, since Cython emits catch handlers for rmm's exception types that it had resolved through the client. Verified: no undefined rmm/raft/cuda symbols, no librmm in DT_NEEDED, still no DT_NEEDED on another cuOpt library, C++ suite 129/129, Python suite 175 passed / 20 skipped. Closes #1890 Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

check_symbols.sh answers a different question: it inspects exported symbols and filters undefined ones away, never reading DT_NEEDED, so a change reintroducing rmm, raft, CUDA or another component would pass it unnoticed. check_client_is_leaf.sh asserts all three, and the recipe runs it for libcuopt_client.so. Confirmed it detects rather than merely passes: it fails on libcuopt_mathopt.so for all three reasons, which legitimately has them. cython_types_gpu.hpp uses std::move, so it includes <utility> directly. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

Every library goes through check_symbols.sh, so the client's extra condition belongs there behind --require-leaf rather than in a second script invoked only for it. Argument parsing now takes any combination of flags and rejects unknown ones. Verified all four invocations: the three current ones pass, and mathopt with --require-leaf fails on all three conditions, so the check detects rather than merely passes. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

The leaf check grepped demangled undefined symbols with ^(rmm|raft)::, which misses 'typeinfo for rmm::...' and 'vtable for rmm::...'. That is not hypothetical: dropping rmm::rmm from cuopt_client surfaced exactly 'undefined symbol: typeinfo for rmm::bad_alloc' in the gRPC extension, and the anchored pattern matched 1 of its 3 undefined rmm symbols. Unanchored it matches all three. gpu_holder_deleter_t asserts instead of silently leaking when a holder has a live pointer and no deleter, which only a construction bug can produce. Also refreshes comments still naming gpu_solutions_t / gpu_buffer, and notes why the factories use plain new/delete rather than an RMM resource. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

…vJitLink The undefined-symbol pattern missed __cudaRegisterFatBinary, which any CUDA translation unit emits, and the DT_NEEDED pattern missed libnvrtc and libnvJitLink. A client carrying either would have passed. Client still passes and mathopt still fails on all three conditions. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

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⚠️ Outside diff range comments (1)

🟠 Major · Remove the explicit librmm runtime requirement. · recipe.yaml:141

conda/recipes/libcuopt/recipe.yaml:141
🗄️ Data Integrity & Integration | 🟠 Major | ⚡ Quick win

Remove the explicit librmm runtime requirement.

--require-leaf verifies that libcuopt_client.so does not need RMM. However, this explicit requirement still installs librmm with every libcuopt-client package. ignore_run_exports cannot remove an explicitly declared runtime dependency.

Remove this entry after confirming that the installed client package does not expose a runtime RMM requirement. This completes the leaf-package contract stated by this PR.
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In `@conda/recipes/libcuopt/recipe.yaml` at line 141, Remove the explicit librmm
runtime dependency from the recipe’s requirements, preserving the remaining
package requirements and the leaf-package contract for libcuopt-client.

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Outside diff comments:
In `@conda/recipes/libcuopt/recipe.yaml`:
- Line 141: Remove the explicit librmm runtime dependency from the recipe’s
requirements, preserving the remaining package requirements and the leaf-package
contract for libcuopt-client.

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The client's public headers pull in nvtx, whose inline init calls dlopen/dlsym, so a consumer compiling them needs -ldl on its own link line. rmm::rmm supplied that transitively until #1890 dropped it, and ${CMAKE_DL_LIBS} was PRIVATE, so the arm64 conda-cpp-build failed linking GRPC_ROUTING_PROBLEM_MAPPER_TEST -- which names cuopt_client alone -- with undefined references to dlopen and dlsym. dl is libc rather than GPU stack, so the client stays a CUDA-free leaf: --require-leaf still passes. Co-Authored-By: Claude Opus 5 <noreply@anthropic.com>

ramakrishnap-nv requested review from a team as code owners September 18, 2026 17:38

ramakrishnap-nv requested review from Bubullzz, Iroy30, akifcorduk and jakirkham September 18, 2026 17:38

ramakrishnap-nv added improvement Improves an existing functionality non-breaking Introduces a non-breaking change labels Sep 18, 2026

ramakrishnap-nv marked this pull request as draft September 18, 2026 17:44

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ramakrishnap-nv force-pushed the fix/client-drop-rmm branch from 7cbd9cd to 443498a Compare September 18, 2026 17:54

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ramakrishnap-nv marked this pull request as ready for review September 18, 2026 20:05

ramakrishnap-nv and others added 3 commits September 18, 2026 21:53

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fix(client): hold the GPU variant alternatives behind an opaque pointer - #1940

fix(client): hold the GPU variant alternatives behind an opaque pointer#1940
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