On 02.07.2013 23:55, Óscar Fuentes wrote:
Nico and Howard,
Nico Rieck <[email protected]> writes:
On 02.07.2013 19:53, Howard Hinnant wrote:
+#elif defined(_WIN32)
+ SYSTEM_INFO info;
+ GetSystemInfo(&info);
+ return info.dwNumberOfProcessors;
#else // defined(CTL_HW) && defined(HW_NCPU)
I'm not that familiar with the implementation for the other platforms,
but this snippet returns the number of logical processors. In my local
Windows port I use the number of cores, as I think that's more
appropriate. This is also what MSVCRT does on Windows.
As per my interpretation of the standard, returning the number of
logical processors is the right thing.
I checked VS2013 on a hyperthreaded machine and
std::thread::hardware_concurrency does just that. Same for
boost::thread::hardware_concurrency.
Did they change that? VS2012 uses GetLogicalProcessorInformation/Ex for
Vista/7+, and GetSystemInfo below. Boost seems to use the latter.
And if people use this to (for example) determine the amount of threads
to spawn, number of cores makes more sense to me.
-Nico
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