implementation of std::thread::hardware_concurrency()

[Iain Sandoe]

On 7 Nov 2011, at 13:45, Jonathan Wakely wrote:

> This provides a working thread::hardware_concurrency on platforms that
> support pthread_num_processors_np or the "hw.ncpu" sysctl, but by
> testing for the features in configure rather than hardcoding OS macro
> tests in thread.cc

if the system supports run-time User-controllable core-count then this  
will not account for that.


>
>        * acinclude.m4 (GLIBCXX_CHECK_SC_NPROC_ONLN): Define.
>        (GLIBCXX_CHECK_PTHREADS_NUM_PROCESSORS_NP): Define.
>        (GLIBCXX_CHECK_SYSCTL_HW_NCPU): Define.
>        * configure.ac: Use new checks.
>        * configure: Regenerate.
>        * config.h.in: Regenerate.
>        * src/thread.cc: Check new config macros.
>        * testsuite/lib/libstdc++.exp: Likewise.
>
> Tested x86_64-linux and x86_64-netbsd5.1, committed to trunk
> <nprocs.patch>