OpenMP在许多平台(包括Visual Studio 2005)上都得到了支持，并且它提供了一种支持

int omp_get_num_procs();

函数返回调用时可用的处理器/核数。

C++11

#include <thread>

//may return 0 when not able to detect
const auto processor_count = std::thread::hardware_concurrency();

参考:std::线程::hardware_concurrency

在c++ 11之前的c++中，没有可移植的方法。相反，你需要使用以下一个或多个方法(由适当的#ifdef行保护):

Win32 SYSTEM_INFO sysinfo; GetSystemInfo(&sysinfo); int numCPU = sysinfo.dwNumberOfProcessors; Linux, Solaris, AIX and Mac OS X >=10.4 (i.e. Tiger onwards) int numCPU = sysconf(_SC_NPROCESSORS_ONLN); FreeBSD, MacOS X, NetBSD, OpenBSD, etc. int mib[4]; int numCPU; std::size_t len = sizeof(numCPU); /* set the mib for hw.ncpu */ mib[0] = CTL_HW; mib[1] = HW_AVAILCPU; // alternatively, try HW_NCPU; /* get the number of CPUs from the system */ sysctl(mib, 2, &numCPU, &len, NULL, 0); if (numCPU < 1) { mib[1] = HW_NCPU; sysctl(mib, 2, &numCPU, &len, NULL, 0); if (numCPU < 1) numCPU = 1; } HPUX int numCPU = mpctl(MPC_GETNUMSPUS, NULL, NULL); IRIX int numCPU = sysconf(_SC_NPROC_ONLN); Objective-C (Mac OS X >=10.5 or iOS) NSUInteger a = [[NSProcessInfo processInfo] processorCount]; NSUInteger b = [[NSProcessInfo processInfo] activeProcessorCount];

OS X替代方案:根据文档，前面描述的基于[[NSProcessInfo processInfo] processorCount]的解决方案仅在OS X 10.5.0上可用。对于较早版本的OS X，使用Carbon函数MPProcessors()。

如果你是一个Cocoa程序员，不要被这是Carbon这个事实吓到。你只需要将Carbon框架添加到你的Xcode项目中，MPProcessors()就可以使用了。

Note that "number of cores" might not be a particularly useful number, you might have to qualify it a bit more. How do you want to count multi-threaded CPUs such as Intel HT, IBM Power5 and Power6, and most famously, Sun's Niagara/UltraSparc T1 and T2? Or even more interesting, the MIPS 1004k with its two levels of hardware threading (supervisor AND user-level)... Not to mention what happens when you move into hypervisor-supported systems where the hardware might have tens of CPUs but your particular OS only sees a few.

最好的情况是告诉您在本地OS分区中拥有的逻辑处理单元的数量。除非您是管理程序，否则不要考虑看到真正的机器。今天这个规则唯一的例外是在x86领域，但非虚拟机的末日很快就会到来……

OpenMP在许多平台(包括Visual Studio 2005)上都得到了支持，并且它提供了一种支持

int omp_get_num_procs();

函数返回调用时可用的处理器/核数。

Windows Server 2003及以后版本允许您利用GetLogicalProcessorInformation函数

http://msdn.microsoft.com/en-us/library/ms683194.aspx