c++ - 以编程方式查找机器上的内核数

Question

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内核？如果不存在这样的东西，如何确定每个平台(Windows/*nix/Mac)？

Answer 1

C++11

#include <thread>

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

引用:std::thread::hardware_concurrency

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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):

• Win32

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

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

  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];