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YACLib
Yet Another Concurrency Library
Table of Contents
About YACLib
YACLib is a lightweight C++ library for concurrent and parallel task execution, that is striving to satisfy the following properties:
- Zero cost abstractions
- Easy to use
- Easy to build
- Good test coverage
For more details check our design document and documentation.
Getting started
For quick start just paste this code in your CMakeLists.txt file.
include(FetchContent)
FetchContent_Declare(yaclib
GIT_REPOSITORY https://github.com/YACLib/YACLib.git
GIT_TAG main
)
FetchContent_MakeAvailable(yaclib)
link_libraries(yaclib)For more details check install guide.
Examples
Here are short examples of using some features from YACLib, for details check documentation.
Asynchronous pipeline
auto tp = yaclib::MakeThreadPool(/*threads=*/4);
yaclib::Run(*tp, [] {
return 42;
}).Then([](int r) {
return r * 2;
}).Then([](int r) {
return r + 1;
}).Then([](int r) {
return std::to_string(r);
}).Detach([](std::string r) {
std::cout << "Pipeline result: <" << r << ">" << std::endl;
});
};Thread Pool
auto tp = yaclib::MakeThreadPool(/*threads=*/4);
Submit(*tp, [] {
// some computations...
});
Submit(*tp, [] {
// some computations...
});
tp->Stop();
tp->Wait();Strand, Serial Executor, Async Mutex
auto tp = yaclib::MakeThreadPool(4);
// decorated thread pool by serializing tasks:
auto strand = yaclib::MakeStrand(tp);
size_t counter = 0;
auto tp2 = yaclib::MakeThreadPool(4);
for (std::size_t i = 0; i < 100; ++i) {
Submit(*tp2, [&] {
Submit(*strand, [&] {
++counter; // no data race!
});
});
}WhenAll
auto tp = yaclib::MakeThreadPool(/*threads=*/4);
std::vector<yaclib::Future<int>> fs;
// Run parallel computations
for (std::size_t i = 0; i < 5; ++i) {
fs.push_back(yaclib::Run(*tp, [i]() -> int {
return random() * i;
}));
}
// Will be ready when all futures are ready
yaclib::Future<std::vector<int>> all = WhenAll(fs.begin(), fs.size());
std::vector<int> unique_ints = std::move(all).Then([](std::vector<int> ints) {
ints.erase(std::unique(ints.begin(), ints.end()), ints.end());
return ints;
}).Get().Ok();WhenAny
auto tp = yaclib::MakeThreadPool(/*threads=*/4);
std::vector<yaclib::Future<int>> fs;
// Run parallel computations
for (std::size_t i = 0; i < 5; ++i) {
fs.push_back(yaclib::Run(*tp, [i] {
// connect with one of the database shard
return i;
}));
}
// Will be ready when any future is ready
WhenAny(fs.begin(), fs.size()).Detach([](int i) {
// some work with database
});Future unwrapping
Sometimes it is necessary to return from one async function the result of the other. It would be possible with the wait on this result. But this would cause blocking thread while waiting for the task to complete.
This problem can be solved using future unwrapping: when an async function returns a Future object, instead of setting its result to the Future object, the inner Future will "replace" the outer Future. This means that the outer Future will complete when the inner Future finishes and will acquire the result of the inner Future.
auto tp_output = yaclib::MakeThreadPool(/*threads=*/1);
auto tp_compute = yaclib::MakeThreadPool(/*threads=CPU cores*/);
auto future = yaclib::Run(*tp_output, [] {
std::cout << "Outer task" << std::endl;
return yaclib::Run(*tp_compute, [] { return 42; });
}).Then(/*tp_compute*/ [](int result) {
result *= 13;
return yaclib::Run(*tp_output, [result] {
return std::cout << "Result = " << result << std::endl;
});
});Timed wait
auto tp = yaclib:MakeThreadPool(/*threads=*/4);
yaclib::Future<int> f1 = yaclib::Run(*tp, [] { return 42; });
yaclib::Future<double> f2 = yaclib::Run(*tp, [] { return 15.0; });
WaitFor(10ms, f1, f2); // or Wait / WaitUntil
if (f1.Ready()) {
Process(std::as_const(f1).Get());
yaclib::util::Result<int> res1 = std::as_const(f1).Get();
assert(f1.Valid()); // f1 valid here
}
if (f2.Ready()) {
Process(std::move(f2).Get());
assert(!f2.Valid()); // f2 invalid here
}Exception recovering
auto tp = yaclib::MakeThreadPool(/*threads=*/4);
auto f = yaclib::Run(*tp, [] {
if (random() % 2) {
throw std::runtime_error{"1"};
}
return 42;
}).Then([](int y) {
if (random() % 2) {
throw std::runtime_error{"2"};
}
return y + 15;
}).Then([](int z) { // Will not run if we have any error
return z * 2;
}).Then([](std::exception_ptr e) { // Recover from error codes
try {
std::rethrow_exception(e);
} catch (const std::runtime_error& e) {
std::cout << e.what() << std::endl;
}
return 10; // Some default value
});
int x = std::move(f).Get().Value();Error recovering
auto tp = yaclib::MakeThreadPool(/*threads=*/4);
auto f = yaclib::Run<std::error_code>(tp, [] {
if (random() % 2) {
return std::make_error_code(1);
}
return 42;
}).Then([](int y) {
if (random() % 2) {
return std::make_error_code(2);
}
return y + 15;
}).Then([](int z) { // Will not run if we have any error
return z * 2;
}).Then([](std::error_code ec) { // Recover from error codes
std::cout << ec.value() << std::endl;
return 10; // Some default value
});
int x = std::move(f).Get().Value();Use Result for smart recovering
auto tp = yaclib::MakeThreadPool(/*threads=*/4);
auto f = yaclib::Run(*tp, [] {
if (random() % 2) {
return std::make_error_code(1);
}
return 42;
}).Then([](int y) {
if (random() % 2) {
throw std::runtime_error{"2"};
}
return y + 15;
}).Then([](yaclib::util::Result<int> z) {
if (!z) {
return 10; // Some default value
}
return z.Value();
});
int x = std::move(f).Get().Value();Requirements
YACLib is a static library, that uses CMake as a build system and requires a compiler with C++17 or newer.
If the library doesn't compile on some compiler satisfying this condition, please create an issue. Pull requests with fixes are welcome!
We can also try to support older standards. If you are interested in it, check this discussion.
We test following configurations:
| OS\Compiler | Linux | Windows | macOS | Android |
|---|---|---|---|---|
| GCC | ||||
| Clang | ||||
| AppleClang | — | — | — | |
| MSVC | — | — | — |
Releases
YACLib follows the Abseil Live at Head philosophy (update to the latest commit from the main branch as often as possible).
So we recommend using the latest commit in the main branch in your projects.
However, we realize this philosophy doesn't work for every project, so we also provide Releases.
Contributing
We are always open for issues and pull requests. For more details you can check following links:
Contacts
You can contact us by our emails:
Or join our Discord Server
License
YACLib is made available under MIT License. See LICENSE file for details.
We would be glad if you let us know that you're using our library.
