concurrencpp | Modern concurrency for C++ | Reactive Programming library

concurrencpp is a C++ library typically used in Programming Style, Reactive Programming applications. concurrencpp has no bugs, it has no vulnerabilities, it has a Permissive License and it has medium support. You can download it from GitHub.

concurrencpp is a task-centric library. A task is an asynchronous operation. Tasks offer a higher level of abstraction for concurrent code than traditional thread-centric approaches. Tasks can be chained together, meaning that tasks pass their asynchronous result from one to another, where the result of one task is used as if it were a parameter or an intermediate value of another ongoing task. Tasks allow applications to utilize available hardware resources better and scale much more than using raw threads, since tasks can be suspended, waiting for another task to produce a result, without blocking underlying OS-threads. Tasks bring much more productivity to developers by allowing them to focus more on business-logic and less on low-level concepts like thread management and inter-thread synchronization. While tasks specify what actions have to be executed, executors are worker-objects that specify where and how to execute tasks. Executors spare applications the managing of thread pools and task queues themselves. Executors also decouple those concepts away from application code, by providing a unified API for creating and scheduling tasks. Tasks communicate with each other using result objects. A result object is an asynchronous pipe that pass the asynchronous result of one task to another ongoing-task. Results can be awaited and resolved in a non-blocking manner. These three concepts - the task, the executor and the associated result are the building blocks of concurrencpp. Executors run tasks that communicate with each-other by sending results through result-objects. Tasks, executors and result objects work together symbiotically to produce concurrent code which is fast and clean. concurrencpp is built around the RAII concept. In order to use tasks and executors, applications create a runtime instance in the beginning of the main function. The runtime is then used to acquire existing executors and register new user-defined executors. Executors are used to create and schedule tasks to run, and they might return a result object that can be used to marshal the asynchronous result to another task that acts as its consumer. When the runtime is destroyed, it iterates over every stored executor and calls its shutdown method. Every executor then exits gracefully. Unscheduled tasks are destroyed, and attempts to create new tasks will throw an exception. In this basic example, we created a runtime object, then we acquired the thread executor from the runtime. We used submit to pass a lambda as our given callable. This lambda returns void, hence, the executor returns a result object that marshals the asynchronous result back to the caller. main calls get which blocks the main thread until the result becomes ready. If no exception was thrown, get returns void. If an exception was thrown, get re-throws it. Asynchronously, thread_executor launches a new thread of execution and runs the given lambda. It implicitly co_return void and the task is finished. main is then unblocked. In this example, we start the program by creating a runtime object. We create a vector filled with random numbers, then we acquire the thread_pool_executor from the runtime and call count_even. count_even is a coroutine that spawns more tasks and co_awaits for them to finish inside. max_concurrency_level returns the maximum amount of workers that the executor supports, In the threadpool executor case, the number of workers is calculated from the number of cores. We then partition the array to match the number of workers and send every chunk to be processed in its own task. Asynchronously, the workers count how many even numbers each chunk contains, and co_return the result. count_even sums every result by pulling the count using co_await, the final result is then co_returned. The main thread, which was blocked by calling get is unblocked and the total count is returned. main prints the number of even numbers and the program terminates gracefully.