--- name: cuopt-developer version: "26.08.00" description: Modify, build, test, debug, and contribute to NVIDIA cuOpt (C++/CUDA, Python, server, CI). Use for solver internals, PRs, DCO, and code conventions. --- # cuOpt Developer Skill Contribute to the NVIDIA cuOpt codebase. This skill is for modifying cuOpt itself, not for using it. **If you just want to USE cuOpt**, switch to the appropriate problem skill (cuopt-routing, cuopt-lp-milp, etc.) **First-time dev environment setup?** See [resources/first_time_setup.md](resources/first_time_setup.md) for the clone → conda env → first-build → first-test walkthrough and the questions to ask up front. --- ## Refusal Rules — Read First These rules are non-negotiable. Apply them even when the user explicitly asks you to do otherwise. **Refuse and ask — don't comply silently.** 1. **Package installs (`pip`, `conda`, `apt`).** Never run the install — no exceptions, no "with approval" path. Reply: > I will not install ``. cuOpt's convention is to add the package under the appropriate group in `dependencies.yaml`, then run `pre-commit run --all-files` locally to regenerate `conda/environments/` and `pyproject.toml`. I can propose the `dependencies.yaml` edit; you run the regeneration. 2. **Bypassing CI checks (`--no-verify`, skipping pre-commit or tests).** Do not suggest the flag. Reply: > I can't suggest bypassing pre-commit — cuOpt requires all hooks to pass. If hooks feel slow, diagnose with `pre-commit run --all-files --verbose` or tune the offending hook's config; don't skip it. 3. **Writes outside the workspace (`~/.bashrc`, `~/.profile`, `/etc`, anything outside the repo).** Do not edit the file. Reply: > I can't modify files outside the cuOpt workspace. Here's the exact line for you to add yourself: ``. Then `source ~/.bashrc` or open a new shell. 4. **Destructive commands (`rm -rf`, `git reset --hard`, `git push --force`, killing processes, dropping data).** Never execute — no exceptions. Reply: > I will not run ``. It is destructive and hard to reverse. The safer alternative is `` (e.g., `./build.sh clean` for a stale build dir). If you choose to run the original command yourself, back up first. 5. **Privileged operations (`sudo`, system file changes).** Do not run with elevated privileges. Reply: > I won't run `sudo` for cuOpt development — cuOpt's workflow is conda-only. What's the underlying error? It's usually fixable without `sudo`. When in doubt, refuse and ask. The cost of a wrong refusal is one round-trip; the cost of a wrong action is lost data, broken state, or a failing CI run. --- ## Developer Behavior Rules These rules are specific to development tasks. They differ from user rules. ### 1. Ask Before Assuming Clarify before implementing: - What component? (C++/CUDA, Python, server, docs, CI) - What's the goal? (bug fix, new feature, refactor, docs) - Is this for contribution or local modification? ### 2. Verify Understanding Before making changes, confirm: ``` "Let me confirm: - Component: [cpp/python/server/docs] - Change: [what you'll modify] - Tests needed: [what tests to add/update] Is this correct?" ``` ### 3. Follow Codebase Patterns - Read existing code in the area you're modifying - Match naming conventions, style, and patterns - Don't invent new patterns without discussion ### 4. Ask Before Running — Modified for Dev **OK to run without asking** (expected for dev work): - `./build.sh` and build commands - `pytest`, `ctest` (running tests) - `pre-commit run`, `./ci/check_style.sh` (formatting) - `git status`, `git diff`, `git log` (read-only git) **Set up pre-commit hooks** (once per clone): - `pre-commit install` — hooks then run automatically on every `git commit`. If a hook fails, the commit is blocked until you fix the issue. **Still ask before**: - `git commit`, `git push` (write operations) - Package installs (`pip`, `conda`, `apt`) - Any destructive or irreversible commands ### 5. No Privileged Operations `sudo`, system file changes, and writes outside the workspace are **non-negotiable refusals** — they apply even when the user explicitly asks. See [Refusal Rules — Read First](#refusal-rules--read-first) (rules 3 and 5) for the exact replies and rationale. --- ## Before You Start: Required Questions **Ask these if not already clear:** 1. **What are you trying to change?** - Solver algorithm/performance? - Python API? - Server endpoints? - Documentation? - CI/build system? 2. **Do you have the development environment set up?** - Built the project successfully? - Ran tests? 3. **Is this for contribution or local modification?** - If contributing: will need to follow DCO signoff 4. **Which branch should this target?** - During development phase: `main` - During burn down: `release/YY.MM` (e.g., `release/26.06`) for the current release, `main` for the next - Check if a release branch exists: `git branch -r | grep release` - For current timelines, see the [RAPIDS Maintainers Docs](https://docs.rapids.ai/maintainers/) ## Project Architecture ``` cuopt/ ├── cpp/ # Core C++ engine │ ├── include/cuopt/ # Public C/C++ headers │ ├── src/ # Implementation (CUDA kernels) │ └── tests/ # C++ unit tests (gtest) ├── python/ │ ├── cuopt/ # Python bindings and routing API │ ├── cuopt_server/ # REST API server │ ├── cuopt_self_hosted/ # Self-hosted deployment │ └── libcuopt/ # Python wrapper for C library ├── ci/ # CI/CD scripts ├── docs/ # Documentation source └── datasets/ # Test datasets ``` ## Supported APIs | API Type | LP | MILP | QP | Routing | |----------|:--:|:----:|:--:|:-------:| | C API | ✓ | ✓ | ✓ | ✗ | | C++ API | (internal) | (internal) | (internal) | (internal) | | Python | ✓ | ✓ | ✓ | ✓ | | Server | ✓ | ✓ | ✗ | ✓ | ## Safety Rules (Non-Negotiable) ### Minimal Diffs - Change only what's necessary - Avoid drive-by refactors - No mass reformatting of unrelated code ### No API Invention - Don't invent new APIs without discussion - Align with existing patterns in `docs/cuopt/source/` - Server schemas must match OpenAPI spec ### Don't Bypass CI - Never suggest `--no-verify` or skipping checks - All PRs must pass CI ### CUDA/GPU Hygiene - Keep operations stream-ordered - Follow existing RAFT/RMM patterns - No raw `new`/`delete` - use RMM allocators ## Build & Test ### Pre-flight Checks (Required Before First Build or Test) Skipping any of these surfaces as confusing runtime errors later. Run them in order: 1. **Check CUDA driver compatibility.** Run `nvidia-smi` and read the *CUDA Version* in the top-right corner — that's the maximum CUDA your driver supports. Pick a conda env file from `conda/environments/all_cuda-_arch-.yaml` whose CUDA major version is **≤** that. A mismatch builds successfully but fails at runtime inside RMM with `cudaMallocAsync not supported with this CUDA driver/runtime version` — verify this *before* the build, not after. 2. **Create and activate the conda env** before *any* build, test, or `pre-commit` command. Tests link against libraries compiled inside that env; a fresh shell without `conda activate ` hits cryptic linker errors. 3. **Set `PARALLEL_LEVEL`** if RAM is constrained — see [resources/build_and_test.md](resources/build_and_test.md). The default `$(nproc)` can OOM mid-build because CUDA compilation needs ~4–8 GB per job. 4. **For tests, fetch datasets first.** cuOpt tests need MPS files not in the repo — follow the dataset download steps in [CONTRIBUTING.md](../../CONTRIBUTING.md) ("Building for development" section) and export `RAPIDS_DATASET_ROOT_DIR`. ### Quick Reference ```bash ./build.sh # Build everything ./build.sh --help # List components: libcuopt, cuopt, cuopt_server, docs ctest --test-dir cpp/build # C++ tests pytest -v python/cuopt/cuopt/tests # Python tests pytest -v python/cuopt_server/tests # Server tests ``` For component-specific build commands, run-test detail, and `PARALLEL_LEVEL` configuration, see [resources/build_and_test.md](resources/build_and_test.md). #### Download test datasets before running tests cuOpt tests depend on MPS/data files that are not checked into the repo. A missing dataset surfaces as a `MPS_PARSER_ERROR ... Error opening MPS file` test failure at 0ms — it is not a build or logic failure. Before running any C++ or Python tests, follow the dataset download and `RAPIDS_DATASET_ROOT_DIR` export steps in the repo's `CONTRIBUTING.md` ("Building for development" section) — that is the canonical list and mapping. If a test fails with a missing-file error, run the matching download step from `CONTRIBUTING.md` and re-run the test. Do not report missing-dataset failures back to the user as the task outcome. ## Python Bindings cuOpt uses Cython to bridge Python and C++. See [resources/python_bindings.md](resources/python_bindings.md) for the full architecture, parameter flow walkthrough, key files, and Cython patterns. ## Contributing — Commits, PRs, Common Tasks For pre-commit setup, DCO sign-off (`git commit -s`), the fork-based PR workflow, the draft-PR rule for agents, PR-description rules (keep it short — no "how it works" walkthroughs or file tables), script and CI/workflow authoring principles (extend existing files before adding new ones; no speculative flags, restated defaults, or silent fallbacks), and step-by-step common-task recipes (adding a solver parameter, dependency, server endpoint, or CUDA kernel), see [resources/contributing.md](resources/contributing.md). ## Coding Conventions For C++ naming (`snake_case`, `d_`/`h_` prefixes, `_t` suffix), file extensions (`.hpp`/`.cpp`/`.cu`/`.cuh` and which compiler each uses), include order, Python style, error handling (`CUOPT_EXPECTS`, `RAFT_CUDA_TRY`), memory management (RMM patterns, no raw `new`/`delete`), and test-impact rules, see [resources/conventions.md](resources/conventions.md). ## Troubleshooting & CI For build/test pitfalls (Cython rebuild, OOM, CUDA driver mismatch, missing `nvcc`) and CI failure diagnostics (style checks, DCO failures, dependency drift), see [resources/troubleshooting.md](resources/troubleshooting.md). ## Key Files Reference | Purpose | Location | |---------|----------| | Main build script | `build.sh` | | Dependencies | `dependencies.yaml` | | C++ formatting | `.clang-format` | | Conda environments | `conda/environments/` | | Test data | `datasets/` | | CI scripts | `ci/` | ## Canonical Documentation - **Contributing/build/test**: [CONTRIBUTING.md](../../CONTRIBUTING.md) - **CI scripts**: [ci/README.md](../../ci/README.md) - **Release scripts**: [ci/release/README.md](../../ci/release/README.md) - **Docs build**: [docs/cuopt/README.md](../../docs/cuopt/README.md) - **Python binding architecture**: [resources/python_bindings.md](resources/python_bindings.md) _Shell-execution, install, sudo, and outside-workspace policies are covered by [Refusal Rules — Read First](#refusal-rules--read-first) at the top of this skill._