Senders - A Standard Model for Asynchronous Execution in C++

stdexec is an experimental reference implementation of the Senders model of asynchronous programming proposed by P2300 - std::execution for adoption into the C++ Standard.

Purpose of this Repository:

1. Provide a proof-of-concept implementation of the design proposed in P2300.
2. Provide early access to developers looking to experiment with the Sender model.
3. Colloborate with those interested in participating or contributing to the design of P2300 (contributions welcome!).

Disclaimer

stdexec is experimental in nature and subject to change without warning. The authors and NVIDIA do not guarantee that this code is fit for any purpose whatsoever.

Example

Below is a simple program that parallelizes some compute intensive work by executing it on a thread pool.

#include <stdexec/execution.hpp>
#include <exec/static_thread_pool.hpp>
#include <vector>
#include <print> // from C++23

extern int compute(int);

int main()
{
    // Declare a pool of 8 worker threads:
    exec::static_thread_pool pool(8);

    // Get a handle to the thread pool:
    auto sched = pool.get_scheduler();

    // Describe some work:
    auto fun = [](int i) { return compute(i); };
    auto work = stdexec::when_all(
        stdexec::on(sched, stdexec::just(0) | stdexec::then(fun)),
        stdexec::on(sched, stdexec::just(1) | stdexec::then(fun)),
        stdexec::on(sched, stdexec::just(2) | stdexec::then(fun))
    );

    // Launch the work and wait for the result:
    auto [i, j, k] = stdexec::sync_wait(std::move(work)).value();

    // Print the results:
    std::print("{}, {}, {}", i, j, k);
}

Structure

This library is header-only, so all the source code can be found in the include/ directory. The physical and logical structure of the code can be summarized by the following table:

Kind	Path	Namespace
Things approved for the C++ standard	<stdexec/...>	::stdexec
Generic additions and extensions	<exec/...>	::exec
Vendor-specific extensions and customizations	<(vendor)exec/...>	::(vendor)exec

Building

The following tools are needed:

• CMake
• One of the following supported C++ compilers:
  • GCC 11+
  • clang 12+
  • nvc++ 22.11

Perform the following actions:

# Configure the project
cmake -S . -B build -G<gen>
# Build the project
cmake --build build

Here, <gen> can be Ninja, "Unix Makefiles", XCode, "Visual Studio 15 Win64", etc.

Specifying the compiler

You can set the C++ compiler via -D CMAKE_CXX_COMPILER:

# Use GCC:
cmake -S . -B build/g++ -DCMAKE_CXX_COMPILER=$(which g++)
cmake --build build/g++

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

Specifying the stdlib

If you want to use libc++ with clang instead of libstdc++, you can specify the standard library as follows:

# Do the actual build
cmake -S . -B build/clang++ -G<gen> \
    -DCMAKE_CXX_FLAGS=-stdlib=libc++ \
    -DCMAKE_CXX_COMPILER=$(which clang++)

cmake --build build/clang++