Sze Howe Koh schreef op 17-3-2015 om 16:15: > Hi, > > On 17 March 2015 at 23:06, Syam Krishnan <sya...@gmail.com> wrote: >> On 03/17/2015 08:03 PM, André Somers wrote: >>> Might I suggest a third method? Use QtConcurrent::run(yourFunction) >>> instead. >> The documentation on QtConcurrent::run() says >> "Note that the function may not run immediately; the function will only >> be run when a thread is available." > These threads are part of the global thread pool. The documentation > means, *if you are currently using all available threads in the pool*, > then QtConcurrent::run() will wait until one of those threads finish > before running. However, since you only want one instance running at a > time, then it's not a problem -- your function will run immediately. Well, in any multi-threaded programming, you basicaly have no control over when something runs. That's up to the OS, not you. It will usually be "soonish", but... >> That is not acceptable to me. I am looking for the simplest solution >> that has the least overhead. > QtConcurrent::run() is the simplest solution available. > > QtConcurrent uses QThreadPool internally. One of the reasons > QThreadPool was created was to reduce the overhead of starting new > threads. Indeed. And that makes it quite a light solution. > >> And I should have mentioned that only one instance of do_something() >> must be executing at any time. >> I am using QAtomicInt to control calls to this function. So when a >> second event is raised, it will check if >> the thread is already executing. If it is, it will wait till the thread >> execution is complete. > Yes, that is compatible with QtConcurrent::run(). In fact, it is easier. Simply check the state of the future. No need for a QAtomicInt who's value is not self-evident. No need to really wait for the value/state to change either: you can attach a QFutureWatcher and get a notification when the future is finished. That way, you don't waste cycles bussy-waiting for another thread.
André _______________________________________________ Interest mailing list Interest@qt-project.org http://lists.qt-project.org/mailman/listinfo/interest
