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A function can also hold a promise object directly and do other processing first (including starting other asynchronous tasks), delaying awaiting the promise until its result is needed. Functions with promises also have promise aggregation methods that allow the program to await multiple promises at once or in some special pattern (such as C#'s ...
As an example of the first possibility, in C++11, a thread that needs the value of a future can block until it is available by calling the wait() or get() member functions. A timeout can also be specified on the wait using the wait_for() or wait_until() member functions to avoid indefinite blocking.
When one thread starts executing the critical section (serialized segment of the program) the other thread should wait until the first thread finishes. If proper synchronization techniques [ 1 ] are not applied, it may cause a race condition where the values of variables may be unpredictable and vary depending on the timings of context switches ...
An algorithm is lock-free if, when the program threads are run for a sufficiently long time, at least one of the threads makes progress (for some sensible definition of progress). All wait-free algorithms are lock-free. In particular, if one thread is suspended, then a lock-free algorithm guarantees that the remaining threads can still make ...
The V operation is the inverse: it makes a resource available again after the process has finished using it. One important property of semaphore S is that its value cannot be changed except by using the V and P operations. A simple way to understand wait (P) and signal (V) operations is: wait: Decrements the value of the semaphore variable by 1.
minimizing wait time (time from work becoming ready until the first point it begins execution); minimizing latency or response time (time from work becoming ready until it is finished in case of batch activity, [ 1 ] [ 2 ] [ 3 ] or until the system responds and hands the first output to the user in case of interactive activity); [ 4 ]
For example, concurrent processes can be executed on one core by interleaving the execution steps of each process via time-sharing slices: only one process runs at a time, and if it does not complete during its time slice, it is paused, another process begins or resumes, and then later the original process is resumed. In this way, multiple ...
One benefit of a thread pool over creating a new thread for each task is that thread creation and destruction overhead is restricted to the initial creation of the pool, which may result in better performance and better system stability. Creating and destroying a thread and its associated resources can be an expensive process in terms of time.