以编程方式查找机器上的内核数

2021-12-02 00:00:00 multithreading c c++ multiplatform

有没有办法以独立于平台的方式从 C/C++ 确定一台机器有多少个内核?如果不存在这样的东西，那么按平台(Windows/*nix/Mac)确定它怎么样?

Is there a way to determine how many cores a machine has from C/C++ in a platform-independent way? If no such thing exists, what about determining it per-platform (Windows/*nix/Mac)?

推荐答案

C++11

#include <thread>

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

参考:std::thread::hardware_concurrency

在 C++11 之前的 C++ 中，没有可移植的方式.相反，您需要使用以下一种或多种方法(由适当的 #ifdef 行保护):

In C++ prior to C++11, there's no portable way. Instead, you'll need to use one or more of the following methods (guarded by appropriate #ifdef lines):

  • Win32

SYSTEM_INFO sysinfo;
GetSystemInfo(&sysinfo);
int numCPU = sysinfo.dwNumberOfProcessors;

  • Linux、Solaris、AIX 和 Mac OS X >=10.4(即 Tiger 以上)

    int numCPU = sysconf(_SC_NPROCESSORS_ONLN);

  • FreeBSD、MacOS X、NetBSD、OpenBSD 等

    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 或 iOS)

    NSUInteger a = [[NSProcessInfo processInfo] processorCount];
NSUInteger b = [[NSProcessInfo processInfo] activeProcessorCount];

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