This is the mail archive of the
libstdc++@gcc.gnu.org
mailing list for the libstdc++ project.
Re: implementation of std::thread::hardware_concurrency()
- From: niXman <i dot nixman at gmail dot com>
- To: gcc-patches at gcc dot gnu dot org, libstdc++ at gcc dot gnu dot org
- Date: Tue, 1 Nov 2011 15:33:01 +0400
- Subject: Re: implementation of std::thread::hardware_concurrency()
- References: <CAMPTgK2Fph+jQBtKQ+nHa7+BMdUCu=zT3dWaUO0pc7z=Xg8mWg@mail.gmail.com> <0223B132-51E6-4B54-8C2D-0EC690A5E9E0@oracle.com>
Rechecked.
diff --git a/libstdc++-v3/src/thread.cc b/libstdc++-v3/src/thread.cc
index 09e7fc5..6feda4d 100644
--- a/libstdc++-v3/src/thread.cc
+++ b/libstdc++-v3/src/thread.cc
@@ -112,10 +112,20 @@ _GLIBCXX_BEGIN_NAMESPACE_VERSION
unsigned int
thread::hardware_concurrency() noexcept
{
- int __n = _GLIBCXX_NPROCS;
- if (__n < 0)
- __n = 0;
- return __n;
+ int count=0;
+#if defined(PTW32_VERSION) || \
+ (defined(__MINGW64_VERSION_MAJOR) && defined(_POSIX_THREADS)) || \
+ defined(__hpux)
+ count=pthread_num_processors_np();
+#elif defined(__APPLE__) || defined(__FreeBSD__)
+ size_t size=sizeof(count);
+ sysctlbyname("hw.ncpu", &count, &size, NULL, 0);
+#elif defined(_SC_NPROCESSORS_ONLN)
+ count=sysconf(_SC_NPROCESSORS_ONLN);
+#elif defined(_GLIBCXX_USE_GET_NPROCS)
+ count=_GLIBCXX_NPROCS;
+#endif
+ return (count>0)?count:0;
}
_GLIBCXX_END_NAMESPACE_VERSION
2011/11/1 Paolo Carlini <pcarlini@gmail.com>:
> Hi,
>
>> This is patch is implement the std::thread::hardware_concurrency().
>> Tested on pthreads-win32/winpthreads on windows OS, and on Linux/FreeBSD.
>
> Please send library patches to the library mailing list too. Also, always parch mainline first: actually in the latter the function is alread implemented, maybe something is missing for win32, please check, rediff, and resend.
>
> Thanks
> Paolo