[Interest] QThreadPool wait until all queued threads are finished

[Federico Ferri]

Why don't you use a QSemaphore?

You instantiate it with n=0 (the default constructor).

Call sem.acquire(xxx.size()) to wait for all tasks to complete, amnd call
sem.release(1) after each task completes.

Best regards,
Federico Ferri

On Tue, Aug 17, 2021 at 9:03 PM Scott Bloom <scott at towel42.com> wrote:

> Here is the problem Im having.  I have background task, that is small
> enough to use a lambda on a given string.
>
>
>
> std::list< yyy > xxx;
>
> for( auto && ii : xxx )
>
> {
>      QThreadPool::globalInstance()->start(
>
>         [ii]()
>
>         {
>
>             doSomething( ii );
>
>         } );
>
> }
>
>
>
> Works great for this… However, I want the application waiting until all
> threads are completed before exiting the tool.
>
>
>
> while (QThreadPool::globalInstance()->activeThreadCount())
>
> {
>
>         QThreadPool::globalInstance()->waitForDone(100);
>
>         qApp->processEvents();
>
> }
>
>
>
> Should work.  Wait 100ms, and continue.
>
>
>
> However, the problem Im having, is activeThreadCount does not take into
> account queued threads.
>
>
>
> Is there a better way?  The length of the xxx can be in the millions, and
> is recursive.
>
>
> Scott
>
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>
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