Main merge release/26.06 05

[ramakrishnap-nv]

For #1317

[coderabbitai]

Caution

Review failed

Pull request was closed or merged during review

📝 Walkthrough

Walkthrough

This PR adds an objective-step lattice feature for MIP optimization and refactors gRPC code generation from hand-written mappers to a declarative YAML registry with auto-generated .inc includes. The objective-step feature enables the solver to snap optimization problems onto objective lattices; the gRPC changes centralize type mappings and reduce hand-written boilerplate.

Changes

Objective Step Lattice Feature

Layer / File(s)	Summary
Objective Step Type System & Constants cpp/src/dual_simplex/user_problem.hpp, cpp/include/cuopt/linear_programming/mip/solver_settings.hpp, cpp/include/cuopt/linear_programming/constants.h	Introduces objective_step_t<f_t> struct with step_size and bias fields, extends user_problem_t and mip_solver_settings_t with objective step storage, and adds CUOPT_MIP_OBJECTIVE_STEP parameter constant.
Rational Utilities & Lattice Propagation cpp/src/cuts/rational.hpp, cpp/src/cuts/objective_step.hpp, cpp/src/cuts/objective_step.cpp, cpp/src/cuts/CMakeLists.txt	Implements continued-fraction rational approximation, rational128_t type with GCD operations, and core propagate_lattice() function that discovers per-variable lattice steps via equality/inequality constraint analysis; includes template instantiations for double and float.
Objective Step Integration in MIP & B&B cpp/src/dual_simplex/presolve.hpp, cpp/src/dual_simplex/presolve.cpp, cpp/src/mip_heuristics/problem/problem.cuh, cpp/src/mip_heuristics/problem/problem.cu, cpp/src/mip_heuristics/solver.cu, cpp/src/branch_and_bound/branch_and_bound.cpp, cpp/src/math_optimization/solver_settings.cu, cpp/src/cuts/cuts.cpp	Adds objective_step member to lp_problem_t and problem_t classes; implements compute_objective_step() with fast lattice-known and slow propagation paths; updates branch-and-bound update_tree_impl and solve_node_lp to use objective-step lattice for lower-bound and LP cut-off calculations; registers parameter in solver settings with min/max bounds; consolidates rational-approximation logic from cuts.cpp to rational.hpp.
Host-Oriented Accessor for Quadratic Objective cpp/include/cuopt/linear_programming/cpu_optimization_problem.hpp	Adds get_quadratic_objective_*_host() override methods that expose CPU-resident quadratic objective data.

gRPC Code Generation Refactoring

Layer / File(s)	Summary
Build Infrastructure & Verification build.sh, ci/test_cpp.sh, ci/verify_grpc_codegen.sh, cpp/CMakeLists.txt	Adds codegen build target to delete and regenerate gRPC outputs; creates verify_grpc_codegen.sh script that compares generated temp output against committed artifacts and reports mismatches/orphans; integrates verification as CI test gate; updates CMakeLists to explicitly path generated proto directory and generate separate cuopt_remote_data.proto step.
Field Registry, Proto Splitting & Dependencies cpp/src/grpc/codegen/field_registry.yaml, cpp/src/grpc/cuopt_remote.proto, cpp/src/grpc/cuopt_remote_service.proto, conda/environments/*.yaml, dependencies.yaml	Introduces comprehensive 917-line YAML field registry defining enums, LP/MIP solutions, solver settings, and optimization problem schemas with field mappings, optional/sentinel markers, and code-generation directives; splits data-bearing types into generated cuopt_remote_data.proto; keeps protocol-level messages in cuopt_remote.proto; adds ResultArrayDescriptor and ChunkedResultHeader to generated data proto; updates conda and dependencies.yaml to include ruamel.yaml>=0.18 for YAML processing.
gRPC Code Generation & Interface Documentation cpp/src/grpc/GRPC_CODE_GENERATION.md, cpp/src/grpc/GRPC_INTERFACE.md	Documents registry schema, enum/message/settings definitions, field allocation strategy, and how generated .inc files are consumed by mappers; specifies chunked transfer protocol flow, automatic size-based routing, and error handling for large problem/result handling.
gRPC Mapper Refactoring to Generated Includes cpp/src/grpc/grpc_problem_mapper.cpp, cpp/src/grpc/grpc_settings_mapper.cpp, cpp/src/grpc/grpc_solution_mapper.cpp	Replaces large hand-written implementations of map_problem_to_proto, map_proto_to_problem, settings mappers, and solution mappers with generated .inc include blocks; consolidates chunking/byte-conversion helpers under anonymous namespaces; adds explicit post-decode sanitization for PDLP/MIP enum ranges and iteration_limit overflow protection; changes bytes_to_typed to throw std::invalid_argument on misaligned payload.
gRPC Solution Mapper Header & Helper Updates cpp/src/grpc/grpc_solution_mapper.hpp, cpp/src/grpc/server/grpc_field_element_size.hpp, cpp/src/grpc/server/grpc_incumbent_proto.hpp	Removes termination-status protobuf conversion declarations; adds chunked-result support declarations for size estimation, header population, array collection, and solution reconstruction; replaces hand-written ArrayFieldId element-size switch with generated include; updates path reference in incumbent proto comment.

gRPC Tests & Test Infrastructure

Layer / File(s)	Summary
Test CMakeLists & Parameter Support cpp/tests/linear_programming/grpc/CMakeLists.txt, python/cuopt/cuopt/tests/linear_programming/test_lp_solver.py	Adds generated proto codegen directory to gRPC test include paths; extends _non_default_solver_param_value to handle mip_objective_step by toggling between 0/1.
gRPC Mapper Roundtrip & Presence Tests cpp/tests/linear_programming/grpc/grpc_client_test.cpp	Expands MIPSettingsAllFields to set/verify symmetry and heuristic parameters; adds MIPSettingsSymmetryClampsOutOfRange test for enum boundary handling; extends PDLPSettingsAllFields with additional solver config fields; introduces optional-field presence tests verifying C++ defaults are preserved when proto fields are omitted; adds comprehensive "default proto preserves C++ defaults" sanity tests for both PDLP and MIP settings.
Proto Serialization Test Updates cpp/tests/linear_programming/grpc/grpc_pipe_serialization_test.cpp	Updates problem-category constant usage from fully-qualified cuopt::remote::LP/MIP to unqualified enum; changes MIP error-message field from set_mip_error_message() to set_error_message().

---

Estimated code review effort

🎯 4 (Complex) | ⏱️ ~60 minutes

---

Possibly related PRs

• NVIDIA/cuopt#1239: Parallel implementation of the objective step feature end-to-end for MIP optimization.
• NVIDIA/cuopt#1103: Modifies branch-and-bound solve_node_lp cutoff logic; overlaps with objective-step lower-bound/cutoff changes in this PR.
• NVIDIA/cuopt#1107: Earlier gRPC code-generation boilerplate setup; directly related to this PR's codegen verification and registry-driven refactoring.

---

Suggested labels

mip, grpc, code-generation

---

Suggested reviewers

• Iroy30
• chris-maes
• tmckayus

🚥 Pre-merge checks | ✅ 3 | ❌ 2

❌ Failed checks (1 warning, 1 inconclusive)

Check name	Status	Explanation	Resolution
Docstring Coverage	⚠️ Warning	Docstring coverage is 12.05% which is insufficient. The required threshold is 80.00%.	Write docstrings for the functions missing them to satisfy the coverage threshold.
Title check	❓ Inconclusive	The title 'Main merge release/26.06 05' is vague and generic, using non-descriptive terms that don't clearly convey the main changes in the changeset.	Revise the title to clearly summarize the primary changes, such as 'Add objective step tightening and gRPC code generation from YAML' or similar descriptive phrasing.

✅ Passed checks (3 passed)

Check name	Status	Explanation
Description check	✅ Passed	The description references issue #1317 and the PR objectives provide clear context about the two main features: YAML-driven gRPC code generation and objective step tightening for MIP solvers.
Linked Issues check	✅ Passed	Check skipped because no linked issues were found for this pull request.
Out of Scope Changes check	✅ Passed	Check skipped because no linked issues were found for this pull request.

_{✏️ Tip: You can configure your own custom pre-merge checks in the settings.}

✨ Finishing Touches

🧪 Generate unit tests (beta)

• Create PR with unit tests

---

_{Comment @coderabbitai help to get the list of available commands and usage tips.}