>
> > 2. There is some plan to develop it?
> >
> Yes, and no. So far, no one has submitted the patches that would make this
> possible (i.e. extend the GCC win32 threading implemenation and lat
> libstdc++ use that). An alternative path would be to create a separate
> implementation of the relevant functionality in libstdc++, written directly
> on top of the Win32 API.
> Fortunately for you though, I recently (well, a couple months ago) learned
> about an implementation of the second option available here:
> https://github.com/meganz/mingw-std-threads
> The author so kindly relicensed the files under the MinGW-w64 runtime
> license, which is essentially public domain or Zlib license where public
> domain doesn't exist.
> I'm curious as to how good that implementation would perform for you!
> Ruben
Thanks Ruben for taking time to answer me.
I have workaround this issue defining my own mutex based on CRITICAL
SECTIONS, here is the implementation:
https://github.com/official-stockfish/Stockfish/blob/master/src/thread_win32.h
I have redefined Mutex instead of std::mutex and defined also my own
condition variable but, with a small loss of speed, would be possible to
use std::condition_variable_any instead. There is no need to replace
std::thread.
With the above implementation I have fully fixed the speed loss.
It all boils down to the mutex implementation that is (by far) sub-optimal,
as I have found googling around:
/// STL thread library used by mingw and gcc when cross compiling for
Windows
/// relies on libwinpthread. Currently libwinpthread implements mutexes
directly
/// on top of Windows semaphores. Semaphores, being kernel objects, require
kernel
/// mode transition in order to lock or unlock, which is very slow compared
to
/// interlocked operations.
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