cpu.cpp

#include <unistd.h>
#include <iostream>
#include <thread>

int getNumberOfCPUs(void)
{
    unsigned concurentThreadsSupported = std::thread::hardware_concurrency();
    // std::cout << "Thread: " << concurentThreadsSupported << std::endl;
#if defined _WIN32
    SYSTEM_INFO sysinfo;
#if (defined(_M_ARM) || defined(_M_ARM64) || defined(_M_X64) || defined(WINRT)) && _WIN32_WINNT >= 0x501
    GetNativeSystemInfo( &sysinfo );
#else
    GetSystemInfo( &sysinfo );
#endif

    return (int)sysinfo.dwNumberOfProcessors;
#elif defined __ANDROID__
    static int ncpus = getNumberOfCPUsImpl();
    return ncpus;
#elif defined __linux__ || defined __GLIBC__ || defined __HAIKU__ || defined __EMSCRIPTEN__
    // return (int)sysconf( _SC_NPROCESSORS_ONLN );
    cpu_set_t cpu_set;
    sched_getaffinity(0, sizeof(cpu_set), &cpu_set);
    // std::cout << "CPU: " <<  CPU_COUNT(&cpu_set) << std::endl;
    return CPU_COUNT(&cpu_set);
#elif defined __APPLE__
    int numCPU=0;
    int mib[4];
    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;
    }

    return (int)numCPU;
#else
    return 1;
#endif
}