Can I know the number of computer cores through the program?

//return 0 if detect fails.
unsigned concurentThreadsSupported = std::thread::hardware_concurrency();

SYSTEM_INFO sysinfo;
GetSystemInfo( &sysinfo );

numCPU = sysinfo.dwNumberOfProcessors;

numCPU = sysconf( _SC_NPROCESSORS_ONLN );

int mib[4];
size_t len = sizeof(numCPU); 

/* /* set the mib for hw.ncpu */
mib[0] = CTL_HW;
mib[1] = HW_AVAILCPU; // If this doesn't work, 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;
     }
}

numCPU = mpctl(MPC_GETNUMSPUS, NULL, NULL);

numCPU = sysconf( _SC_NPROC_ONLN );

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