---
id: pr-cccl-cub-8080
repo: NVIDIA/cccl
pr: 8080
title: Implement `is_root_rank` and `is_part_of` queries for groups
author: davebayer
date: '2026-03-19'
url: https://github.com/NVIDIA/cccl/pull/8080
source_category: upstream-code
architectures:
- sm100
tags:
- reduction
techniques: []
hardware_features: []
kernel_types:
- reduction
languages: []
captured_at: '2026-05-16'
status: merged
merge_sha: 77e72d5edba1611e8d7f4b26267fc68a0f371e49
inclusion_reason: Search-matched CUDA kernel optimization PR; materialize diff/source before synthesis.
changed_paths:
- cudax/test/hierarchy/group.cu
- libcudacxx/include/cuda/__hierarchy/hierarchy_level_base.h
- libcudacxx/include/cuda/__hierarchy/native_hierarchy_level_base.h
artifact_dir: evidence/pull-bundles/cccl-cub/gh-8080
head_ref_oid: 0e90f6cce64839829d4032bda8814e01e43c88c7
---
# Implement `is_root_rank` and `is_part_of` queries for groups

- Repository: `NVIDIA/cccl`
- PR: [8080](https://github.com/NVIDIA/cccl/pull/8080)
- 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

- `cudax/test/hierarchy/group.cu`
- `libcudacxx/include/cuda/__hierarchy/hierarchy_level_base.h`
- `libcudacxx/include/cuda/__hierarchy/native_hierarchy_level_base.h`

## Evidence Bundle

`evidence/pull-bundles/cccl-cub/gh-8080`
