---
id: pr-cccl-cub-7667
repo: NVIDIA/cccl
pr: 7667
title: Implement the new tuning API for `Dispatch[Streaming]ReduceByKey`
author: bernhardmgruber
date: '2026-02-27'
url: https://github.com/NVIDIA/cccl/pull/7667
source_category: upstream-code
architectures:
- sm100
tags:
- reduction
techniques: []
hardware_features: []
kernel_types:
- reduction
languages: []
captured_at: '2026-05-16'
status: merged
merge_sha: bfc82f0c26331e4b3bb1893fafdeb90890e460c7
inclusion_reason: Search-matched CUDA kernel optimization PR; materialize diff/source before synthesis.
changed_paths:
- cub/benchmarks/bench/reduce/by_key.cu
- cub/benchmarks/bench/run_length_encode/encode.cu
- cub/cub/agent/agent_reduce_by_key.cuh
- cub/cub/detail/delay_constructor.cuh
- cub/cub/device/device_reduce.cuh
- cub/cub/device/device_run_length_encode.cuh
- cub/cub/device/dispatch/dispatch_reduce_by_key.cuh
- cub/cub/device/dispatch/dispatch_streaming_reduce_by_key.cuh
- cub/cub/device/dispatch/tuning/tuning_reduce_by_key.cuh
- cub/cub/device/dispatch/tuning/tuning_rle_encode.cuh
- cub/cub/device/dispatch/tuning/tuning_rle_non_trivial_runs.cuh
- nvbench_helper/nvbench_helper/look_back_helper.cuh
artifact_dir: evidence/pull-bundles/cccl-cub/gh-7667
head_ref_oid: 87f00f775b6fa3dc594a12f5ee0484642d6ecaa1
---
# Implement the new tuning API for `Dispatch[Streaming]ReduceByKey`

- Repository: `NVIDIA/cccl`
- PR: [7667](https://github.com/NVIDIA/cccl/pull/7667)
- Decision: `Search-matched CUDA kernel optimization PR; materialize diff/source before synthesis.`
- Reason: Search-matched CUDA kernel optimization PR; materialize diff/source before synthesis.

## Changed Paths

- `cub/benchmarks/bench/reduce/by_key.cu`
- `cub/benchmarks/bench/run_length_encode/encode.cu`
- `cub/cub/agent/agent_reduce_by_key.cuh`
- `cub/cub/detail/delay_constructor.cuh`
- `cub/cub/device/device_reduce.cuh`
- `cub/cub/device/device_run_length_encode.cuh`
- `cub/cub/device/dispatch/dispatch_reduce_by_key.cuh`
- `cub/cub/device/dispatch/dispatch_streaming_reduce_by_key.cuh`
- `cub/cub/device/dispatch/tuning/tuning_reduce_by_key.cuh`
- `cub/cub/device/dispatch/tuning/tuning_rle_encode.cuh`
- `cub/cub/device/dispatch/tuning/tuning_rle_non_trivial_runs.cuh`
- `nvbench_helper/nvbench_helper/look_back_helper.cuh`

## Evidence Bundle

`evidence/pull-bundles/cccl-cub/gh-7667`
