thread-pool

A simple, functional thread pool implementation using pure C++20.

Features

Built entirely with C++20
Enqueue tasks with or without tracking results

Integration

dp::thread-pool is a header only library. All the files needed are in include/thread_pool.

CMake

ThreadPool defines two CMake targets:

ThreadPool::ThreadPool
dp::thread-pool

You can then use find_package():

find_package(dp::thread-pool REQUIRED)

Alternatively, you can use something like CPM which is based on CMake's Fetch_Content module.

CPMAddPackage(
    NAME thread-pool
    GITHUB_REPOSITORY DeveloperPaul123/thread-pool
    GIT_TAG #0cea9c12fb30cb677696c0dce6228594ce26171a change this to latest commit or release tag
)

Usage

Simple example:

// create a thread pool with a specified number of threads.
dp::thread_pool pool(4);

// add tasks, in this case without caring about results of individual tasks
pool.enqueue_detach([](int value) { /*...your task...*/ }, 34);
pool.enqueue_detach([](int value) { /*...your task...*/ }, 37);
pool.enqueue_detach([](int value) { /*...your task...*/ }, 38);
// and so on..

You can see other examples in the /examples folder.

Benchmarks

See the ./benchmark folder for the benchmark code. The benchmarks are set up to compare matrix multiplication using the dp::thread_pool versus std::async. A summary of the comparisons is below. Benchmarks were run using the windows-release CMake preset (see CMakePresets.json).

Machine Specs

AMD Ryzen 7 1800X (16 X 3593 MHz CPUs)
CPU Caches:
- L1 Data 32 KiB (x8)
- L1 Instruction 64 KiB (x8)
- L2 Unified 512 KiB (x8)
- L3 Unified 8192 KiB (x2)
32 GB RAM

Summary of Results

Matrix sizes are all square (MxM). Each multiplication is (MxM) * (MxM) where * refers to a matrix multiplication operation. Times recorded were the best of at least 3 runs.

Matrix Size	Number of multiplications	`std::async` time (ms)	`dp::thread_pool` time (ms)
8	25,000	77.9	65.3
64	5,000	100	65.2
256	250	295	59.2
512	75	713	60.4
1024	10	1160	55.8

Building

This project has been built with:

Visual Studio 2022
Clang 10.+ (via WSL on Windows)
GCC 11.+ (vis WSL on Windows)
CMake 3.21+

To build, run:

cmake -S . -B build
cmake --build build

Build Options

Option	Description	Default
`TP_BUILD_TESTS`	Turn on to build unit tests. Required for formatting build targets.	ON
`TP_BUILD_EXAMPLES`	Turn on to build examples	ON

Run clang-format

Use the following commands from the project's root directory to check and fix C++ and CMake source style. This requires clang-format, cmake-format and pyyaml to be installed on the current system. To use this feature you must turn on TP_BUILD_TESTS.

# view changes
cmake --build build/test --target format

# apply changes
cmake --build build/test --target fix-format

See Format.cmake for details.

Build the documentation

The documentation is automatically built and published whenever a GitHub Release is created. To manually build documentation, call the following command.

cmake -S documentation -B build/doc
cmake --build build/doc --target GenerateDocs
# view the docs
open build/doc/doxygen/html/index.html

To build the documentation locally, you will need Doxygen and Graphviz on your system.

Contributing

Contributions are very welcome. Please see contribution guidelines for more info.

License

The project is licensed under the MIT license. See LICENSE for more details.

Author

_{@DeveloperPaul123}

Flig / thread-pool