andrewmusselman opened a new pull request, #1321:
URL: https://github.com/apache/mahout/pull/1321
Fixes Issue #1318 .
`qdp-core/build.rs` (extended; it already existed for protoc) now:
- probes for `nvcc` with the same logic as `qdp-kernels/build.rs`,
- emits `cargo:rustc-link-search=native=$CUDA_PATH/lib64` and
`cargo:rustc-link-lib=cudart` when found,
- emits `cargo:rustc-cfg=qdp_no_cuda` when not found, with a clear
`cargo:warning` pointing at the toolkit install,
- respects `QDP_NO_CUDA=1` for explicit forcing (matching `qdp-kernels`).
`qdp-core/src/gpu/cuda_ffi.rs` wraps the `extern "C"` block in
`#[cfg(not(qdp_no_cuda))]` and adds matching `#[cfg(qdp_no_cuda)] mod
no_cuda_stubs { ... }` with `pub(crate) unsafe fn` stubs for all 14
declared functions. Each stub returns `999` — the same sentinel
`qdp-kernels` uses for its kernel-launcher stubs — so existing caller
error paths (`if ret != 0 { return Err(...) }`) surface a clean runtime
error if anyone calls a CUDA function on a no-toolkit build, instead of
failing at link time. The whole stub module is wrapped in a single
`#[allow(non_snake_case)]` since the originals are camelCase to match
the real CUDA Runtime API.
Cross-crate behaviour after this PR:
| environment | qdp-kernels | qdp-core | result
|
|--------------------------|-------------------|------------------|-------------------------|
| toolkit installed | links cudart | links cudart | normal
GPU build |
| driver only / macOS / CI | stub launchers | stub Runtime API | links;
runtime err 999 |
| `QDP_NO_CUDA=1` | stub launchers | stub Runtime API | links;
runtime err 999 |
Verified on Linux + CUDA 12.4: `cargo build --workspace --tests
--exclude qdp-python` succeeds both with and without `QDP_NO_CUDA=1`;
`make test_rust` runs full integration tests on the GPU; 12 lint
warnings introduced by the stubs are silenced.
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