Is there an implementation of std :: async that uses the thread pool?

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The standard function std::async:

The template function async runs the function f asynchronously (potentially in a separate thread which may be part of a thread pool) and returns a std::future that will eventually hold the result of that function call.

There is two launch polices std::launch::async and std::launch::deferred. In my compiler's (GCC 6.2) standard library impelmentation, the first one always creates a new thread and the second one does lazy evaluation on the calling thread. By default std::launch::deferred is used.

Is there some implementation which uses thread pool with size equal to the hardware threads available when std::launch::async is specified to avoid creating two many threads when std::async is used in recursive algorithm?


Microsoft's compiler and C++ runtime that it ships with Visual Studio does.