viiccwen opened a new pull request, #916:
URL: https://github.com/apache/mahout/pull/916
### Purpose of PR
This PR implements GPU-accelerated L2 norm calculation for single float32
vectors, which is a foundational component for supporting float32 CUDA tensor
encoding in QDP.
## Changes
### CUDA Kernels (`qdp/qdp-kernels/src/amplitude.cu`)
- Added `warp_reduce_sum_f32()` helper function for efficient warp-level
reduction using shuffle instructions
- Added `block_reduce_sum_f32()` helper function for block-level reduction
using shared memory
- Added `l2_norm_kernel_f32()` kernel that:
- Uses `float2` vectorized loads for 64-bit memory transactions
- Processes 2 elements per thread for optimal memory bandwidth
- Uses warp/block reduction for efficient sum accumulation
- Supports arbitrary input lengths (handles odd lengths correctly)
- Added `finalize_inv_norm_kernel_f32()` kernel to convert accumulated
sum-of-squares to inverse norm using `rsqrtf()`
- Added `launch_l2_norm_f32()` launch function with proper grid size
calculation and error handling
### Rust Bindings (`qdp/qdp-kernels/src/lib.rs`)
- Added `launch_l2_norm_f32` function declaration.
- Added dummy implementation for non-Linux platforms (returns error code 999)
### Tests (`qdp/qdp-kernels/tests/amplitude_encode.rs`)
- Added `test_l2_norm_single_kernel_f32()` test case
- Test verifies correctness against CPU calculation
### Related Issues or PRs
closes #915
### Changes Made
<!-- Please mark one with an "x" -->
- [ ] Bug fix
- [x] New feature
- [ ] Refactoring
- [ ] Documentation
- [x] Test
- [ ] CI/CD pipeline
- [ ] Other
### Breaking Changes
<!-- Does this PR introduce a breaking change? -->
- [ ] Yes
- [x] No
### Checklist
<!-- Please mark each item with an "x" when complete -->
<!-- If not all items are complete, please open this as a **Draft PR**.
Once all requirements are met, mark as ready for review. -->
- [x] Added or updated unit tests for all changes
- [ ] Added or updated documentation for all changes
- [x] Successfully built and ran all unit tests or manual tests locally
- [x] PR title follows "MAHOUT-XXX: Brief Description" format (if related to
an issue)
- [x] Code follows ASF guidelines
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