stdexec — Senders for C++

A reference implementation of std::execution ([exec]), the C++26 model for asynchronous and parallel programming.

stdexec lets you express asynchronous work as composable, lazy sender pipelines that can run on threads, thread pools, GPUs, or any custom execution context — with structured concurrency guarantees.

[!WARNING] stdexec is experimental and tracks an evolving standard. APIs may change without notice. NVIDIA does not guarantee fitness for any particular purpose.

Table of contents

• Example
• Features
• Compiler support
• Installation
• Quick start
• GPU support
• Examples gallery
• Documentation
• Building tests and examples
• IDE support
• Resources
• Contributing
• Citation
• License

Example

Run three pieces of work concurrently on the system thread pool. Try it live on godbolt.

#include <stdexec/execution.hpp>
#include <cstdio>

namespace ex = stdexec;

int main() {
    auto sched = ex::get_parallel_scheduler();
    auto fun   = [](int i) { return i * i; };

    // Build a lazy pipeline: three squares, computed in parallel.
    auto work = ex::when_all(ex::on(sched, ex::just(0) | ex::then(fun)),
                             ex::on(sched, ex::just(1) | ex::then(fun)),
                             ex::on(sched, ex::just(2) | ex::then(fun)));

    // Launch the work and wait for the result.
    auto [i, j, k] = ex::sync_wait(std::move(work)).value();
    std::printf("%d %d %d\n", i, j, k); // prints "0 1 4"
}

Features

• C++26 reference implementation of std::execution (P2300).
• Header-only, no external dependencies.
• Composable algorithms: then, let_value, when_all, bulk, split, transfer, upon_*, ...
• Structured concurrency primitives: async_scope, task, finally, when_any, repeat_n, ...
• Pluggable schedulers: system parallel scheduler, static thread pool, Linux io_uring context, NVIDIA GPU contexts, your own.
• GPU offload via nvexec schedulers (nvc++ compiler).
• Coroutine interop: senders are awaitable; awaitables are senders.
• Generic extensions (<exec/...>) for primitives not (yet) in the standard.

Compiler support

Requires -std=c++20 or later.

[!NOTE] stdexec does not yet support NVIDIA's nvcc compiler.

Installation

Pick whichever fits your project.

CPM (recommended)

CPM fetches and configures stdexec automatically from your CMakeLists.txt:

CPMAddPackage(
  NAME stdexec
  GITHUB_REPOSITORY NVIDIA/stdexec
  GIT_TAG main  # or a specific tag
)

target_link_libraries(my_target PRIVATE STDEXEC::stdexec)

add_subdirectory

Clone alongside your project and add it as a subdirectory:

git clone https://github.com/NVIDIA/stdexec.git

add_subdirectory(stdexec)
target_link_libraries(my_target PRIVATE STDEXEC::stdexec)

Conan

A conanfile.py is provided for use with the Conan package manager.

NVIDIA HPC SDK

Starting with NVHPC SDK 22.11, stdexec is bundled with nvc++. Pass --experimental-stdpar to put stdexec headers on the include path. Add -stdpar=gpu for GPU features. See the godbolt example.

Manual include path

stdexec is header-only, so adding -I<stdexec root>/include to your compile command is sufficient. Using the CMake target is recommended because it sets the required compile flags.

Quick start

A minimal CMakeLists.txt using CPM:

cmake_minimum_required(VERSION 3.25.0)
project(stdexec_example LANGUAGES CXX)

include(CPM.cmake)  # see https://github.com/cpm-cmake/CPM.cmake#adding-cpm

CPMAddPackage(
  NAME stdexec
  GITHUB_REPOSITORY NVIDIA/stdexec
  GIT_TAG main
)

add_executable(example example.cpp)
target_link_libraries(example PRIVATE STDEXEC::stdexec)

GPU support

stdexec ships GPU schedulers in <nvexec/...> for use with nvc++ -stdpar=gpu:

Live example: https://godbolt.org/z/h7rh5qGhj

Examples gallery

The examples/ directory contains runnable programs demonstrating the library.

Documentation

📖 Full documentation: https://nvidia.github.io/stdexec

• User guide: https://nvidia.github.io/stdexec/user/ (source)
• Reference: https://nvidia.github.io/stdexec/reference/ (source)
• Developer docs: https://nvidia.github.io/stdexec/developer/ (source)
• Contributing to docs: docs/CONTRIBUTING-docs.md
• The proposal: [exec] — std::execution

The library is organized into three namespaces:

Building tests and examples

The library itself is header-only — these steps are only needed if you want to build the test suite or the examples.

cmake -S . -B build -G Ninja
cmake --build build
ctest --test-dir build

To select a specific compiler:

cmake -S . -B build/clang -DCMAKE_CXX_COMPILER=$(which clang++)
cmake --build build/clang

To use libc++ with Clang:

cmake -S . -B build/libcxx \
    -DCMAKE_CXX_COMPILER=$(which clang++) \
    -DCMAKE_CXX_FLAGS=-stdlib=libc++
cmake --build build/libcxx

IDE support

A VSCode extension is available that colorizes compiler diagnostics from stdexec, making the long template error messages much easier to read. Source and configuration: https://github.com/ericniebler/buildoutputcolorizer.

Resources

Standards papers

• P2300 — std::execution — the proposal accepted into C++26.

Talks

• Working with Asynchrony Generically: A Tour of Executors (Part 2) — comprehensive introduction.
• From Zero to Sender/Receiver in ~60 Minutes — live-coding a toy sender/receiver from scratch.
• A Unifying Abstraction for Async in C++ — concepts behind P2300.
• Structured Concurrency — what structured concurrency means and why.
• Structured Networking in C++ — what a P2300-style networking library could look like.

Articles and blog posts

• What are Senders Good For, Anyway? — wrapping a C-style async API in a sender.
• A Universal Async Abstraction for C++ — an introduction to senders.
• A Universal I/O Abstraction for C++ — senders meet io_uring.
• Executors: a Change of Perspective — on the computational completeness of senders.
• Structured Concurrency in C++ — how senders manifest structured concurrency.
• HPCWire: New C++ Sender Library Enables Portable Asynchrony.

NVIDIA

• NVIDIA HPC SDK documentation.

Contributing

Contributions are welcome. Before opening a PR, please review:

• CODE_OF_CONDUCT.md
• MAINTAINERS.md
• docs/CONTRIBUTING-docs.md for documentation contributions.

Bug reports and feature requests belong in GitHub Issues; design discussion in GitHub Discussions.

Citation

If you reference stdexec in academic work, please cite the standards proposal:

@techreport{P2300,
  author = {Niebler, Eric and Shoop, Kirk and Baker, Lewis and Dominiak, Michał and
            Evtushenko, Georgy and Teodorescu, Lucian Radu and Howes, Lee and Garland,
            Michael and Lelbach, Bryce Adelstein}
  title  = {{P2300R10}: \texttt{std::execution}},
  institution = {ISO/IEC JTC1/SC22/WG21},
  year   = {2024},
  url    = {https://wg21.link/p2300}
}

License

stdexec is licensed under the Apache License 2.0 with LLVM Exceptions. See LICENSE.txt for the full text.