As far as I can see from the source, if you call QtConcurrent::blockingMap it will block but not use the current thread. If the current thread was allocated by QThreadPool this means cpu utilisation will be reduced.

Is there a reason for this behaviour or any way to avoid it?

I would like to launch a number of concurrent tasks, which may themselves include sections of code parallelised with QtConcurrent. If there are insufficient threads available, these sections should run serially but ideally all cores would be fully used.

Any ideas or recommendations?

thanks.