Add C api callbacks for getting and setting solutions #779
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📝 WalkthroughWalkthroughAdds optional user_data propagation to MIP solution callbacks across C, C++, and Python layers. Introduces new C API MIP callback registration functions, extends callback interfaces and invocation sites to accept a user_data pointer, and updates tests and bindings to pass and validate this pointer. Changes
Estimated code review effort🎯 3 (Moderate) | ⏱️ ~25 minutes 🚥 Pre-merge checks | ✅ 2 | ❌ 1❌ Failed checks (1 warning)
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🚧 Files skipped from review as they are similar to previous changes (1)
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Actionable comments posted: 6
🤖 Fix all issues with AI agents
In `@cpp/include/cuopt/linear_programming/cuopt_c.h`:
- Around line 706-728: The Doxygen for cuOptSetMipGetSolutionCallback and
cuOptSetMipSetSolutionCallback is missing documentation for the new user_data
parameter; update both comment blocks to add a `@param`[in] user_data description
(e.g., "User-defined pointer passed through to the callback") and mention that
it will be forwarded to the respective
cuOptMipGetSolutionCallback/cuOptMipSetSolutionCallback when invoked so the
public API documents the parameter contract.
In `@cpp/include/cuopt/linear_programming/mip/solver_settings.hpp`:
- Around line 37-41: Update the Doxygen block for set_mip_callback to document
the new user_data parameter: add a brief `@param` description for user_data
explaining it is an opaque pointer passed to the callback (e.g., "pointer to
user-defined data forwarded to the callback"), and ensure the existing `@param`
for callback remains accurate; modify the comment above the function declaration
in solver_settings.hpp (the set_mip_callback declaration) so the public API docs
enumerate both callback and user_data.
In `@cpp/include/cuopt/linear_programming/utilities/internals.hpp`:
- Around line 34-36: Add brief Doxygen comments above the public accessor
methods set_user_data and get_user_data describing their purpose: annotate
set_user_data with "Store user-defined context data for callback invocation."
and get_user_data with "Retrieve user-defined context data passed to callbacks."
Place these comments immediately above the corresponding method declarations in
internals.hpp so the public solver callback interface methods are documented per
the header-file documentation guideline.
In `@cpp/src/mip/diversity/diversity_manager.cu`:
- Around line 446-450: There is an unconditional exit(0) that aborts the solver
flow and prevents LP solution handling; remove the exit(0) invocation so
execution continues into the subsequent LP handling (the if
(ls.lp_optimal_exists) block) after calling clamp_within_var_bounds, ensuring
normal callback and MIP behavior; search for the symbols
clamp_within_var_bounds, exit(0), and ls.lp_optimal_exists to locate and delete
the exit call so control can proceed.
In `@cpp/src/mip/solver_settings.cu`:
- Around line 27-31: The set_mip_callback function currently pushes a nullptr
into mip_callbacks_ because it only guards the set_user_data call; update
mip_solver_settings_t<i_t, f_t>::set_mip_callback to first check if callback is
nullptr and if so do not push it (either return early or ignore the call),
otherwise call callback->set_user_data(user_data) and then push_back(callback)
so mip_callbacks_ never contains null entries; this ensures later dereferences
of entries in mip_callbacks_ (e.g., where callbacks are invoked) are safe.
In `@python/cuopt/cuopt/linear_programming/internals/internals.pyx`:
- Around line 70-76: The runtime AttributeError happens because _user_data is
assigned dynamically in the cdef classes; declare the attribute in both callback
extension types (e.g., in the class body of GetSolutionCallback and
SetSolutionCallback) as a Cython Python-object attribute like "cdef object
_user_data" (or "cdef public object _user_data" if you need external access),
then keep the existing __init__ assignment and the get_user_data_ptr cast that
uses self._user_data; ensure the declaration appears in both classes so lines
assigning/reading _user_data no longer raise.
🧹 Nitpick comments (1)
cpp/include/cuopt/linear_programming/solver_settings.hpp (1)
84-85: Documentuser_dataownership/lifetime in the public API.Adding a brief Doxygen note will clarify that the pointer must remain valid for the duration of callback usage and that it’s passed through verbatim.
✍️ Suggested doc addition
- void set_mip_callback(internals::base_solution_callback_t* callback = nullptr, - void* user_data = nullptr); + /** + * Register a MIP solution callback. + * `@param` callback Callback instance (must outlive solver usage). + * `@param` user_data Opaque pointer passed back to the callback; must remain valid + * while the callback can be invoked. + */ + void set_mip_callback(internals::base_solution_callback_t* callback = nullptr, + void* user_data = nullptr);As per coding guidelines, public headers should keep docs in sync with API changes.
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📒 Files selected for processing (16)
cpp/include/cuopt/linear_programming/cuopt_c.hcpp/include/cuopt/linear_programming/mip/solver_settings.hppcpp/include/cuopt/linear_programming/solver_settings.hppcpp/include/cuopt/linear_programming/utilities/callbacks_implems.hppcpp/include/cuopt/linear_programming/utilities/internals.hppcpp/src/linear_programming/cuopt_c.cppcpp/src/math_optimization/solver_settings.cucpp/src/mip/diversity/diversity_manager.cucpp/src/mip/diversity/population.cucpp/src/mip/solver_settings.cucpp/tests/linear_programming/c_api_tests/c_api_test.ccpp/tests/mip/incumbent_callback_test.cupython/cuopt/cuopt/linear_programming/internals/internals.pyxpython/cuopt/cuopt/linear_programming/solver/solver.pxdpython/cuopt/cuopt/linear_programming/solver/solver_wrapper.pyxpython/cuopt/cuopt/linear_programming/solver_settings/solver_settings.py
🚧 Files skipped from review as they are similar to previous changes (1)
- cpp/src/linear_programming/cuopt_c.cpp
🧰 Additional context used
📓 Path-based instructions (8)
**/*.{cu,cuh,cpp,hpp,h}
📄 CodeRabbit inference engine (.github/.coderabbit_review_guide.md)
**/*.{cu,cuh,cpp,hpp,h}: Track GPU device memory allocations and deallocations to prevent memory leaks; ensure cudaMalloc/cudaFree balance and cleanup of streams/events
Validate algorithm correctness in optimization logic: simplex pivots, branch-and-bound decisions, routing heuristics, and constraint/objective handling must produce correct results
Check numerical stability: prevent overflow/underflow, precision loss, division by zero/near-zero, and use epsilon comparisons for floating-point equality checks
Validate correct initialization of variable bounds, constraint coefficients, and algorithm state before solving; ensure reset when transitioning between algorithm phases (presolve, simplex, diving, crossover)
Ensure variables and constraints are accessed from the correct problem context (original vs presolve vs folded vs postsolve); verify index mapping consistency across problem transformations
For concurrent CUDA operations (barriers, async operations), explicitly create and manage dedicated streams instead of reusing the default stream; document stream lifecycle
Eliminate unnecessary host-device synchronization (cudaDeviceSynchronize) in hot paths that blocks GPU pipeline; use streams and events for async execution
Assess algorithmic complexity for large-scale problems (millions of variables/constraints); ensure O(n log n) or better complexity, not O(n²) or worse
Verify correct problem size checks before expensive GPU/CPU operations; prevent resource exhaustion on oversized problems
Identify assertions with overly strict numerical tolerances that fail on legitimate degenerate/edge cases (near-zero pivots, singular matrices, empty problems)
Ensure race conditions are absent in multi-GPU code and multi-threaded server implementations; verify proper synchronization of shared state
Refactor code duplication in solver components (3+ occurrences) into shared utilities; for GPU kernels, use templated device functions to avoid duplication
Check that hard-coded GPU de...
Files:
cpp/include/cuopt/linear_programming/cuopt_c.hcpp/include/cuopt/linear_programming/solver_settings.hppcpp/src/math_optimization/solver_settings.cucpp/src/mip/solver_settings.cucpp/tests/mip/incumbent_callback_test.cucpp/include/cuopt/linear_programming/mip/solver_settings.hppcpp/src/mip/diversity/population.cucpp/include/cuopt/linear_programming/utilities/callbacks_implems.hppcpp/src/mip/diversity/diversity_manager.cucpp/include/cuopt/linear_programming/utilities/internals.hpp
**/*.{h,hpp,py}
📄 CodeRabbit inference engine (.github/.coderabbit_review_guide.md)
Verify C API does not break ABI stability (no struct layout changes, field reordering); maintain backward compatibility in Python and server APIs with deprecation warnings
Files:
cpp/include/cuopt/linear_programming/cuopt_c.hcpp/include/cuopt/linear_programming/solver_settings.hpppython/cuopt/cuopt/linear_programming/solver_settings/solver_settings.pycpp/include/cuopt/linear_programming/mip/solver_settings.hppcpp/include/cuopt/linear_programming/utilities/callbacks_implems.hppcpp/include/cuopt/linear_programming/utilities/internals.hpp
**/*.{cpp,hpp,h}
📄 CodeRabbit inference engine (.github/.coderabbit_review_guide.md)
**/*.{cpp,hpp,h}: Check for unclosed file handles when reading MPS/QPS problem files; ensure RAII patterns or proper cleanup in exception paths
Validate input sanitization to prevent buffer overflows and resource exhaustion attacks; avoid unsafe deserialization of problem files
Prevent thread-unsafe use of global and static variables; use proper mutex/synchronization in server code accessing shared solver state
Files:
cpp/include/cuopt/linear_programming/cuopt_c.hcpp/include/cuopt/linear_programming/solver_settings.hppcpp/include/cuopt/linear_programming/mip/solver_settings.hppcpp/include/cuopt/linear_programming/utilities/callbacks_implems.hppcpp/include/cuopt/linear_programming/utilities/internals.hpp
**/*.{cu,cpp,hpp,h}
📄 CodeRabbit inference engine (.github/.coderabbit_review_guide.md)
Avoid inappropriate use of exceptions in performance-critical GPU operation paths; prefer error codes or CUDA error checking for latency-sensitive code
Files:
cpp/include/cuopt/linear_programming/cuopt_c.hcpp/include/cuopt/linear_programming/solver_settings.hppcpp/src/math_optimization/solver_settings.cucpp/src/mip/solver_settings.cucpp/tests/mip/incumbent_callback_test.cucpp/include/cuopt/linear_programming/mip/solver_settings.hppcpp/src/mip/diversity/population.cucpp/include/cuopt/linear_programming/utilities/callbacks_implems.hppcpp/src/mip/diversity/diversity_manager.cucpp/include/cuopt/linear_programming/utilities/internals.hpp
cpp/include/cuopt/**/*
⚙️ CodeRabbit configuration file
cpp/include/cuopt/**/*: For public header files (C++ API):
- Check if new public functions/classes have documentation comments (Doxygen format)
- Flag API changes that may need corresponding docs/ updates
- Verify parameter descriptions match actual types/behavior
- Suggest documenting thread-safety, GPU requirements, and numerical behavior
- For breaking changes, recommend updating docs and migration guides
Files:
cpp/include/cuopt/linear_programming/cuopt_c.hcpp/include/cuopt/linear_programming/solver_settings.hppcpp/include/cuopt/linear_programming/mip/solver_settings.hppcpp/include/cuopt/linear_programming/utilities/callbacks_implems.hppcpp/include/cuopt/linear_programming/utilities/internals.hpp
**/*.{cu,cuh}
📄 CodeRabbit inference engine (.github/.coderabbit_review_guide.md)
**/*.{cu,cuh}: Every CUDA kernel launch and memory operation must have error checking with CUDA_CHECK or equivalent verification
Avoid reinventing functionality already available in Thrust, CCCL, or RMM libraries; prefer standard library utilities over custom implementations
Files:
cpp/src/math_optimization/solver_settings.cucpp/src/mip/solver_settings.cucpp/tests/mip/incumbent_callback_test.cucpp/src/mip/diversity/population.cucpp/src/mip/diversity/diversity_manager.cu
**/*.cu
📄 CodeRabbit inference engine (.github/.coderabbit_review_guide.md)
**/*.cu: Verify race conditions and correctness of GPU kernel shared memory, atomics, and warp-level operations
Detect inefficient GPU kernel launches with low occupancy or poor memory access patterns; optimize for coalesced memory access and minimize warp divergence in hot paths
Files:
cpp/src/math_optimization/solver_settings.cucpp/src/mip/solver_settings.cucpp/tests/mip/incumbent_callback_test.cucpp/src/mip/diversity/population.cucpp/src/mip/diversity/diversity_manager.cu
**/*test*.{cpp,cu,py}
📄 CodeRabbit inference engine (.github/.coderabbit_review_guide.md)
**/*test*.{cpp,cu,py}: Write tests validating numerical correctness of optimization results (not just 'runs without error'); test degenerate cases (infeasible, unbounded, empty, singleton problems)
Ensure test isolation: prevent GPU state, cached memory, and global variables from leaking between test cases; verify each test independently initializes its environment
Add tests for algorithm phase transitions: verify correct initialization of bounds and state when transitioning from presolve to simplex to diving to crossover
Add tests for problem transformations: verify correctness of original→transformed→postsolve mappings and index consistency across problem representations
Test with free variables, singleton problems, and extreme problem dimensions near resource limits to validate edge case handling
Files:
cpp/tests/mip/incumbent_callback_test.cu
🧠 Learnings (23)
📚 Learning: 2025-10-22T14:25:22.899Z
Learnt from: aliceb-nv
Repo: NVIDIA/cuopt PR: 527
File: cpp/src/mip/diversity/lns/rins.cu:167-175
Timestamp: 2025-10-22T14:25:22.899Z
Learning: In MIP (Mixed Integer Programming) problems in the cuOPT codebase, `n_integer_vars == 0` is impossible by definition—MIP problems must have at least one integer variable. If there are no integer variables, it would be a pure Linear Programming (LP) problem, not a MIP problem.
Applied to files:
cpp/include/cuopt/linear_programming/cuopt_c.hcpp/tests/linear_programming/c_api_tests/c_api_test.c
📚 Learning: 2025-11-25T10:20:49.822Z
Learnt from: CR
Repo: NVIDIA/cuopt PR: 0
File: .github/.coderabbit_review_guide.md:0-0
Timestamp: 2025-11-25T10:20:49.822Z
Learning: Applies to **/*.{cu,cuh,cpp,hpp,h} : Validate algorithm correctness in optimization logic: simplex pivots, branch-and-bound decisions, routing heuristics, and constraint/objective handling must produce correct results
Applied to files:
cpp/include/cuopt/linear_programming/cuopt_c.hcpp/src/mip/diversity/diversity_manager.cucpp/tests/linear_programming/c_api_tests/c_api_test.c
📚 Learning: 2025-11-25T10:20:49.822Z
Learnt from: CR
Repo: NVIDIA/cuopt PR: 0
File: .github/.coderabbit_review_guide.md:0-0
Timestamp: 2025-11-25T10:20:49.822Z
Learning: Applies to **/*.{cu,cuh,cpp,hpp,h} : Check that hard-coded GPU device IDs and resource limits are made configurable; abstract multi-backend support for different CUDA versions
Applied to files:
cpp/include/cuopt/linear_programming/cuopt_c.hcpp/include/cuopt/linear_programming/solver_settings.hppcpp/src/math_optimization/solver_settings.cucpp/src/mip/solver_settings.cucpp/tests/mip/incumbent_callback_test.cucpp/include/cuopt/linear_programming/mip/solver_settings.hppcpp/src/mip/diversity/population.cucpp/include/cuopt/linear_programming/utilities/callbacks_implems.hppcpp/src/mip/diversity/diversity_manager.cucpp/tests/linear_programming/c_api_tests/c_api_test.c
📚 Learning: 2025-11-25T10:20:49.822Z
Learnt from: CR
Repo: NVIDIA/cuopt PR: 0
File: .github/.coderabbit_review_guide.md:0-0
Timestamp: 2025-11-25T10:20:49.822Z
Learning: Applies to **/*.{cu,cuh,cpp,hpp,h} : Track GPU device memory allocations and deallocations to prevent memory leaks; ensure cudaMalloc/cudaFree balance and cleanup of streams/events
Applied to files:
cpp/include/cuopt/linear_programming/cuopt_c.hcpp/include/cuopt/linear_programming/solver_settings.hppcpp/src/math_optimization/solver_settings.cucpp/src/mip/solver_settings.cucpp/tests/mip/incumbent_callback_test.cucpp/include/cuopt/linear_programming/mip/solver_settings.hppcpp/src/mip/diversity/population.cucpp/include/cuopt/linear_programming/utilities/callbacks_implems.hppcpp/src/mip/diversity/diversity_manager.cu
📚 Learning: 2025-11-25T10:20:49.822Z
Learnt from: CR
Repo: NVIDIA/cuopt PR: 0
File: .github/.coderabbit_review_guide.md:0-0
Timestamp: 2025-11-25T10:20:49.822Z
Learning: Applies to **/*.{cu,cuh,cpp,hpp,h} : Ensure race conditions are absent in multi-GPU code and multi-threaded server implementations; verify proper synchronization of shared state
Applied to files:
cpp/include/cuopt/linear_programming/cuopt_c.hcpp/include/cuopt/linear_programming/solver_settings.hppcpp/src/math_optimization/solver_settings.cucpp/src/mip/solver_settings.cucpp/tests/mip/incumbent_callback_test.cucpp/include/cuopt/linear_programming/mip/solver_settings.hppcpp/src/mip/diversity/population.cucpp/include/cuopt/linear_programming/utilities/callbacks_implems.hppcpp/src/mip/diversity/diversity_manager.cu
📚 Learning: 2025-11-25T10:20:49.822Z
Learnt from: CR
Repo: NVIDIA/cuopt PR: 0
File: .github/.coderabbit_review_guide.md:0-0
Timestamp: 2025-11-25T10:20:49.822Z
Learning: Applies to **/*.{cu,cpp,hpp,h} : Avoid inappropriate use of exceptions in performance-critical GPU operation paths; prefer error codes or CUDA error checking for latency-sensitive code
Applied to files:
cpp/include/cuopt/linear_programming/cuopt_c.hcpp/include/cuopt/linear_programming/solver_settings.hppcpp/src/math_optimization/solver_settings.cucpp/src/mip/solver_settings.cucpp/tests/mip/incumbent_callback_test.cucpp/include/cuopt/linear_programming/mip/solver_settings.hppcpp/src/mip/diversity/population.cucpp/include/cuopt/linear_programming/utilities/callbacks_implems.hppcpp/src/mip/diversity/diversity_manager.cu
📚 Learning: 2025-11-25T10:20:49.822Z
Learnt from: CR
Repo: NVIDIA/cuopt PR: 0
File: .github/.coderabbit_review_guide.md:0-0
Timestamp: 2025-11-25T10:20:49.822Z
Learning: Applies to **/*.{cu,cuh,cpp,hpp,h} : Refactor code duplication in solver components (3+ occurrences) into shared utilities; for GPU kernels, use templated device functions to avoid duplication
Applied to files:
cpp/include/cuopt/linear_programming/cuopt_c.hcpp/include/cuopt/linear_programming/solver_settings.hppcpp/src/math_optimization/solver_settings.cucpp/src/mip/solver_settings.cucpp/tests/mip/incumbent_callback_test.cucpp/include/cuopt/linear_programming/mip/solver_settings.hppcpp/src/mip/diversity/population.cucpp/include/cuopt/linear_programming/utilities/callbacks_implems.hppcpp/src/mip/diversity/diversity_manager.cucpp/tests/linear_programming/c_api_tests/c_api_test.c
📚 Learning: 2025-11-25T10:20:49.822Z
Learnt from: CR
Repo: NVIDIA/cuopt PR: 0
File: .github/.coderabbit_review_guide.md:0-0
Timestamp: 2025-11-25T10:20:49.822Z
Learning: Applies to **/*.{cu,cuh,cpp,hpp,h} : Verify error propagation from CUDA to user-facing APIs is complete; ensure CUDA errors are caught and mapped to meaningful user error codes
Applied to files:
cpp/include/cuopt/linear_programming/cuopt_c.hcpp/include/cuopt/linear_programming/solver_settings.hppcpp/src/math_optimization/solver_settings.cucpp/src/mip/solver_settings.cucpp/tests/mip/incumbent_callback_test.cucpp/include/cuopt/linear_programming/mip/solver_settings.hppcpp/src/mip/diversity/population.cucpp/include/cuopt/linear_programming/utilities/callbacks_implems.hppcpp/src/mip/diversity/diversity_manager.cucpp/tests/linear_programming/c_api_tests/c_api_test.c
📚 Learning: 2025-11-25T10:20:49.822Z
Learnt from: CR
Repo: NVIDIA/cuopt PR: 0
File: .github/.coderabbit_review_guide.md:0-0
Timestamp: 2025-11-25T10:20:49.822Z
Learning: Applies to **/*.cu : Verify race conditions and correctness of GPU kernel shared memory, atomics, and warp-level operations
Applied to files:
cpp/include/cuopt/linear_programming/cuopt_c.hcpp/include/cuopt/linear_programming/solver_settings.hppcpp/src/math_optimization/solver_settings.cucpp/src/mip/solver_settings.cucpp/tests/mip/incumbent_callback_test.cucpp/include/cuopt/linear_programming/mip/solver_settings.hppcpp/src/mip/diversity/population.cucpp/include/cuopt/linear_programming/utilities/callbacks_implems.hppcpp/src/mip/diversity/diversity_manager.cu
📚 Learning: 2025-11-25T10:20:49.822Z
Learnt from: CR
Repo: NVIDIA/cuopt PR: 0
File: .github/.coderabbit_review_guide.md:0-0
Timestamp: 2025-11-25T10:20:49.822Z
Learning: Applies to **/*.{cu,cuh,cpp,hpp,h} : Verify correct problem size checks before expensive GPU/CPU operations; prevent resource exhaustion on oversized problems
Applied to files:
cpp/include/cuopt/linear_programming/cuopt_c.hcpp/include/cuopt/linear_programming/solver_settings.hppcpp/src/math_optimization/solver_settings.cucpp/src/mip/solver_settings.cucpp/tests/mip/incumbent_callback_test.cucpp/include/cuopt/linear_programming/mip/solver_settings.hppcpp/include/cuopt/linear_programming/utilities/callbacks_implems.hppcpp/src/mip/diversity/diversity_manager.cucpp/tests/linear_programming/c_api_tests/c_api_test.c
📚 Learning: 2025-11-25T10:20:49.822Z
Learnt from: CR
Repo: NVIDIA/cuopt PR: 0
File: .github/.coderabbit_review_guide.md:0-0
Timestamp: 2025-11-25T10:20:49.822Z
Learning: Applies to **/*.{cu,cuh,cpp,hpp,h} : Eliminate unnecessary host-device synchronization (cudaDeviceSynchronize) in hot paths that blocks GPU pipeline; use streams and events for async execution
Applied to files:
cpp/include/cuopt/linear_programming/cuopt_c.hcpp/src/math_optimization/solver_settings.cucpp/tests/mip/incumbent_callback_test.cucpp/src/mip/diversity/population.cucpp/include/cuopt/linear_programming/utilities/callbacks_implems.hppcpp/src/mip/diversity/diversity_manager.cu
📚 Learning: 2025-11-25T10:20:49.822Z
Learnt from: CR
Repo: NVIDIA/cuopt PR: 0
File: .github/.coderabbit_review_guide.md:0-0
Timestamp: 2025-11-25T10:20:49.822Z
Learning: Applies to **/*.{cu,cuh,cpp,hpp,h} : For concurrent CUDA operations (barriers, async operations), explicitly create and manage dedicated streams instead of reusing the default stream; document stream lifecycle
Applied to files:
cpp/include/cuopt/linear_programming/cuopt_c.hcpp/include/cuopt/linear_programming/solver_settings.hppcpp/src/math_optimization/solver_settings.cucpp/src/mip/solver_settings.cucpp/tests/mip/incumbent_callback_test.cucpp/include/cuopt/linear_programming/mip/solver_settings.hppcpp/src/mip/diversity/population.cucpp/include/cuopt/linear_programming/utilities/callbacks_implems.hpp
📚 Learning: 2025-11-25T10:20:49.822Z
Learnt from: CR
Repo: NVIDIA/cuopt PR: 0
File: .github/.coderabbit_review_guide.md:0-0
Timestamp: 2025-11-25T10:20:49.822Z
Learning: Applies to **/*test*.{cpp,cu,py} : Ensure test isolation: prevent GPU state, cached memory, and global variables from leaking between test cases; verify each test independently initializes its environment
Applied to files:
cpp/include/cuopt/linear_programming/solver_settings.hppcpp/src/mip/solver_settings.cucpp/include/cuopt/linear_programming/mip/solver_settings.hppcpp/src/mip/diversity/population.cucpp/src/mip/diversity/diversity_manager.cucpp/tests/linear_programming/c_api_tests/c_api_test.c
📚 Learning: 2025-11-25T10:20:49.822Z
Learnt from: CR
Repo: NVIDIA/cuopt PR: 0
File: .github/.coderabbit_review_guide.md:0-0
Timestamp: 2025-11-25T10:20:49.822Z
Learning: Applies to **/*.{cu,cuh,cpp,hpp,h} : Validate correct initialization of variable bounds, constraint coefficients, and algorithm state before solving; ensure reset when transitioning between algorithm phases (presolve, simplex, diving, crossover)
Applied to files:
cpp/src/mip/diversity/diversity_manager.cucpp/tests/linear_programming/c_api_tests/c_api_test.c
📚 Learning: 2026-01-15T20:41:51.616Z
Learnt from: chris-maes
Repo: NVIDIA/cuopt PR: 697
File: cpp/src/dual_simplex/diving_heuristics.cpp:200-228
Timestamp: 2026-01-15T20:41:51.616Z
Learning: In cpp/src/dual_simplex/diving_heuristics.cpp, the calculate_variable_locks function incorrectly indexes lp_problem.lower[nz_row] and lp_problem.upper[nz_row] where nz_row is a row index (0 to num_rows-1), but lower and upper are variable bounds of size num_cols indexed by column. This causes semantic errors and potential out-of-bounds access when num_rows > num_cols. Since lp_problem_t constraints are always equalities (A*x = rhs) after presolve, lock counting should treat each nonzero as contributing equally to both up_lock and down_lock, rather than checking constraint bounds.
Applied to files:
cpp/src/mip/diversity/diversity_manager.cu
📚 Learning: 2025-12-04T20:09:09.264Z
Learnt from: chris-maes
Repo: NVIDIA/cuopt PR: 602
File: cpp/src/linear_programming/solve.cu:732-742
Timestamp: 2025-12-04T20:09:09.264Z
Learning: In cpp/src/linear_programming/solve.cu, the barrier solver does not currently return INFEASIBLE or UNBOUNDED status. It only returns OPTIMAL, TIME_LIMIT, NUMERICAL_ISSUES, or CONCURRENT_LIMIT.
Applied to files:
cpp/src/mip/diversity/diversity_manager.cucpp/tests/linear_programming/c_api_tests/c_api_test.c
📚 Learning: 2025-11-25T10:20:49.822Z
Learnt from: CR
Repo: NVIDIA/cuopt PR: 0
File: .github/.coderabbit_review_guide.md:0-0
Timestamp: 2025-11-25T10:20:49.822Z
Learning: Applies to **/*test*.{cpp,cu,py} : Add tests for algorithm phase transitions: verify correct initialization of bounds and state when transitioning from presolve to simplex to diving to crossover
Applied to files:
cpp/tests/linear_programming/c_api_tests/c_api_test.c
📚 Learning: 2025-11-25T10:20:49.822Z
Learnt from: CR
Repo: NVIDIA/cuopt PR: 0
File: .github/.coderabbit_review_guide.md:0-0
Timestamp: 2025-11-25T10:20:49.822Z
Learning: Applies to **/*test*.{cpp,cu,py} : Add tests for problem transformations: verify correctness of original→transformed→postsolve mappings and index consistency across problem representations
Applied to files:
cpp/tests/linear_programming/c_api_tests/c_api_test.c
📚 Learning: 2025-11-25T10:20:49.822Z
Learnt from: CR
Repo: NVIDIA/cuopt PR: 0
File: .github/.coderabbit_review_guide.md:0-0
Timestamp: 2025-11-25T10:20:49.822Z
Learning: Applies to **/*test*.{cpp,cu,py} : Test with free variables, singleton problems, and extreme problem dimensions near resource limits to validate edge case handling
Applied to files:
cpp/tests/linear_programming/c_api_tests/c_api_test.c
📚 Learning: 2025-11-25T10:20:49.822Z
Learnt from: CR
Repo: NVIDIA/cuopt PR: 0
File: .github/.coderabbit_review_guide.md:0-0
Timestamp: 2025-11-25T10:20:49.822Z
Learning: Applies to **/*test*.{cpp,cu,py} : Write tests validating numerical correctness of optimization results (not just 'runs without error'); test degenerate cases (infeasible, unbounded, empty, singleton problems)
Applied to files:
cpp/tests/linear_programming/c_api_tests/c_api_test.c
📚 Learning: 2025-11-25T10:20:49.822Z
Learnt from: CR
Repo: NVIDIA/cuopt PR: 0
File: .github/.coderabbit_review_guide.md:0-0
Timestamp: 2025-11-25T10:20:49.822Z
Learning: Applies to **/*.{cu,cuh,cpp,hpp,h} : Ensure variables and constraints are accessed from the correct problem context (original vs presolve vs folded vs postsolve); verify index mapping consistency across problem transformations
Applied to files:
cpp/tests/linear_programming/c_api_tests/c_api_test.c
📚 Learning: 2025-12-06T00:22:48.638Z
Learnt from: chris-maes
Repo: NVIDIA/cuopt PR: 500
File: cpp/tests/linear_programming/c_api_tests/c_api_test.c:1033-1048
Timestamp: 2025-12-06T00:22:48.638Z
Learning: In cuOPT's quadratic programming API, when a user provides a quadratic objective matrix Q via set_quadratic_objective_matrix or the C API functions cuOptCreateQuadraticProblem/cuOptCreateQuadraticRangedProblem, the API internally computes Q_symmetric = Q + Q^T and the barrier solver uses 0.5 * x^T * Q_symmetric * x. From the user's perspective, the convention is x^T Q x. For a diagonal Q with values [q1, q2, ...], the resulting quadratic terms are q1*x1^2 + q2*x2^2 + ...
Applied to files:
cpp/tests/linear_programming/c_api_tests/c_api_test.c
📚 Learning: 2025-12-04T04:11:12.640Z
Learnt from: chris-maes
Repo: NVIDIA/cuopt PR: 500
File: cpp/src/dual_simplex/scaling.cpp:68-76
Timestamp: 2025-12-04T04:11:12.640Z
Learning: In the cuOPT dual simplex solver, CSR/CSC matrices (including the quadratic objective matrix Q) are required to have valid dimensions and indices by construction. Runtime bounds checking in performance-critical paths like matrix scaling is avoided to prevent slowdowns. Validation is performed via debug-only check_matrix() calls wrapped in `#ifdef` CHECK_MATRIX.
Applied to files:
cpp/tests/linear_programming/c_api_tests/c_api_test.c
🧬 Code graph analysis (7)
cpp/include/cuopt/linear_programming/cuopt_c.h (1)
cpp/src/linear_programming/cuopt_c.cpp (4)
cuOptSetMipGetSolutionCallback(753-764)cuOptSetMipGetSolutionCallback(753-755)cuOptSetMipSetSolutionCallback(766-777)cuOptSetMipSetSolutionCallback(766-768)
cpp/include/cuopt/linear_programming/solver_settings.hpp (2)
cpp/include/cuopt/linear_programming/mip/solver_settings.hpp (1)
callback(40-41)cpp/include/cuopt/linear_programming/utilities/internals.hpp (1)
user_data(35-35)
cpp/src/math_optimization/solver_settings.cu (5)
cpp/src/mip/solver_settings.cu (2)
set_mip_callback(27-32)set_mip_callback(27-28)python/cuopt/cuopt/linear_programming/solver_settings/solver_settings.py (1)
set_mip_callback(248-305)cpp/include/cuopt/linear_programming/mip/solver_settings.hpp (1)
callback(40-41)cpp/include/cuopt/linear_programming/solver_settings.hpp (1)
callback(84-85)cpp/include/cuopt/linear_programming/utilities/internals.hpp (1)
user_data(35-35)
cpp/src/mip/solver_settings.cu (3)
cpp/include/cuopt/linear_programming/mip/solver_settings.hpp (1)
callback(40-41)cpp/include/cuopt/linear_programming/solver_settings.hpp (1)
callback(84-85)cpp/include/cuopt/linear_programming/utilities/internals.hpp (1)
user_data(35-35)
cpp/tests/mip/incumbent_callback_test.cu (3)
cpp/include/cuopt/linear_programming/utilities/callbacks_implems.hpp (12)
data(20-29)data(20-20)data(31-39)data(31-31)data(41-56)data(41-41)data(63-72)data(63-63)data(74-82)data(74-74)data(84-99)data(84-84)cpp/include/cuopt/linear_programming/utilities/internals.hpp (3)
data(47-47)data(56-56)user_data(35-35)cpp/src/linear_programming/cuopt_c.cpp (2)
data(57-63)data(57-57)
cpp/include/cuopt/linear_programming/utilities/internals.hpp (2)
cpp/include/cuopt/linear_programming/utilities/callbacks_implems.hpp (12)
data(20-29)data(20-20)data(31-39)data(31-31)data(41-56)data(41-41)data(63-72)data(63-63)data(74-82)data(74-74)data(84-99)data(84-84)cpp/src/linear_programming/cuopt_c.cpp (4)
data(57-63)data(57-57)data(73-78)data(73-73)
cpp/tests/linear_programming/c_api_tests/c_api_test.c (1)
cpp/src/linear_programming/cuopt_c.cpp (16)
cuOptCreateProblem(140-195)cuOptCreateProblem(140-153)cuOptCreateSolverSettings(619-625)cuOptCreateSolverSettings(619-619)cuOptSetMipGetSolutionCallback(753-764)cuOptSetMipGetSolutionCallback(753-755)cuOptSetMipSetSolutionCallback(766-777)cuOptSetMipSetSolutionCallback(766-768)cuOptSolve(792-840)cuOptSolve(792-794)cuOptDestroyProblem(387-393)cuOptDestroyProblem(387-387)cuOptDestroySolverSettings(627-632)cuOptDestroySolverSettings(627-627)cuOptDestroySolution(842-861)cuOptDestroySolution(842-842)
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- GitHub Check: wheel-build-cuopt-mps-parser / 13.1.0, 3.10, arm64, rockylinux8
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- GitHub Check: wheel-build-cuopt-mps-parser / 13.1.0, 3.12, arm64, rockylinux8
- GitHub Check: wheel-build-cuopt-mps-parser / 13.1.0, 3.13, amd64, rockylinux8
- GitHub Check: wheel-build-cuopt-mps-parser / 13.1.0, 3.13, arm64, rockylinux8
- GitHub Check: wheel-build-cuopt-mps-parser / 13.1.0, 3.11, amd64, rockylinux8
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🔇 Additional comments (16)
python/cuopt/cuopt/linear_programming/solver/solver_wrapper.pyx (1)
185-198: LGTM — user_data is forwarded to the native callback.Nice, this preserves backward compatibility while wiring the user context into
set_mip_callback.python/cuopt/cuopt/linear_programming/solver_settings/solver_settings.py (1)
248-305: LGTM — user_data is preserved on the callback.This keeps the user context alive and aligns with the new callback plumbing.
cpp/src/math_optimization/solver_settings.cu (2)
3-3: No review comment needed.
385-388: LGTM: user_data is forwarded to MIP settings.Clean passthrough that aligns with the new callback API.
cpp/include/cuopt/linear_programming/solver_settings.hpp (1)
3-3: No review comment needed.cpp/src/mip/solver_settings.cu (1)
3-3: No review comment needed.python/cuopt/cuopt/linear_programming/solver/solver.pxd (2)
1-1: No review comment needed.
80-82: LGTM: Cython declaration matches the updated C++ API.The user_data parameter is correctly surfaced here.
cpp/src/mip/diversity/population.cu (2)
3-3: No review comment needed.
302-303: LGTM: user_data is forwarded to both GET and SET callbacks.This keeps the callback context intact through the MIP solution pipeline.
Also applies to: 324-326
python/cuopt/cuopt/linear_programming/internals/internals.pyx (1)
24-32: Signature alignment with native callbacks looks correct.cpp/tests/mip/incumbent_callback_test.cu (2)
43-45: LGTM for the updated set_solution signature.
68-70: LGTM for the updated get_solution signature.cpp/tests/linear_programming/c_api_tests/c_api_test.c (2)
12-12: No issues with the CUDA runtime include.
135-296: Good callback test coverage and cleanup flow.cpp/include/cuopt/linear_programming/utilities/callbacks_implems.hpp (1)
41-55: Backward-compatible user_data handling looks good.Also applies to: 84-98
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Actionable comments posted: 2
🤖 Fix all issues with AI agents
In `@python/cuopt/cuopt/linear_programming/internals/internals.pyx`:
- Around line 86-97: The _user_data attribute and get_user_data_ptr() are
duplicated and lack a setter in GetSolutionCallback/SetSolutionCallback; move
_user_data, its initialization and the get_user_data_ptr() implementation into
the PyCallback base class (add initialization in PyCallback.__init__ and expose
a setter there), remove the duplicated _user_data and get_user_data_ptr() from
GetSolutionCallback and SetSolutionCallback, and ensure subclasses call
super().__init__() (or otherwise inherit) so the native_callback.pyCallbackClass
assignment in their __init__ still references the correct self.
- Around line 66-77: The Cython cdef attribute _user_data is currently C-level
only so Python assigns a shadow attribute (making user_data passed to
set_mip_callback ignored); expose it to Python by adding a Python-accessible
property or declaring it cdef public (e.g., provide a user_data property with
getter/setter that stores the C-level _user_data and returns/accepts a Python
object) in the cdef class (adjust __init__ to use the new property if needed),
ensure get_user_data_ptr() reads the same backing field, and update caller sites
(solver_settings.set_mip_callback and the analogous SetSolutionCallback usage)
to set callback.user_data = user_data instead of callback._user_data = user_data
so the Python-assigned value is visible to get_user_data_ptr().
🧹 Nitpick comments (1)
python/cuopt/cuopt/linear_programming/internals/internals.pyx (1)
72-77: Document the lifetime contract for the returned pointer.The returned
uintptr_tis a borrowed reference — noPy_INCREFis performed. The pointer remains valid only whileself(the callback object) is alive. If C code caches this pointer beyond the callback's lifetime, it risks use-after-free.Consider adding a docstring clarifying that the caller must keep the callback object alive while using the pointer:
cpdef uintptr_t get_user_data_ptr(self): """Return raw pointer to user_data. Valid only while this callback is alive."""
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📒 Files selected for processing (2)
python/cuopt/cuopt/linear_programming/internals/internals.pyxpython/cuopt/cuopt/linear_programming/solver/solver_wrapper.pyx
🚧 Files skipped from review as they are similar to previous changes (1)
- python/cuopt/cuopt/linear_programming/solver/solver_wrapper.pyx
🔇 Additional comments (2)
python/cuopt/cuopt/linear_programming/internals/internals.pyx (2)
11-11: LGTM!Using
cpython.ref cimport PyObjectis the idiomatic Cython approach, cleaner than a manual extern declaration.
21-29: LGTM!The extern declarations correctly extend the callback signatures to include the
user_dataparameter, enabling per-callback user context propagation.
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1 participant
This PR adds callbacks to C API. Users can now use C API to implement get_solution and set_solution callbacks.
Summary by CodeRabbit
New Features
Tests
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