Count Processors using C++ under Windows

Question

Using unmanaged C++ on a Windows platform, is there a simple way to detect the number of processor cores my host machine has?

Answer 1

You can use GetLogicalProcessorInformation to get the info you need.

ETA:

As mentioned in the question a commenter linked to, another (easier) way to do it would be via GetSystemInfo:

SYSTEM_INFO sysinfo;
GetSystemInfo( &sysinfo );

numCPU = sysinfo.dwNumberOfProcessors;

Seems like GetLogicalProcessorInformation would give you more detailed info, but if all you need is the number of processors, GetSystemInfo would probably work just fine.

Answer 2

I've noticed there's an environment variable NUMBER_OF_PROCESSORS on XP, but I couldn't find it on Microsoft's site. I believe this would be the easiest way, though.

Answer 3

Check out GetLogicalProcessorInformation

Answer 4

size_t getProcessorCores()
{
    DWORD process, system;
    if(GetProcessAffinityMask(GetCurrentProcess(), &process, &system))
    {
        int count = 0;
        for(int i = 0; i < 32; i++)
            if(system & (1 << i))
                count++;
        return count;
    }
    // may be we hav't PROCESS_QUERY_INFORMATION access right
    SYSTEM_INFO sysinfo;
    GetSystemInfo( &sysinfo );
    return sysinfo.dwNumberOfProcessors;
}

size_t getAvailableProcessorCores()
{
    DWORD process, system;
    if(GetProcessAffinityMask(GetCurrentProcess(), &process, &system))
    {
        int count = 0;
        for(int i = 0; i < 32; i++)
            if(process & (1 << i))
                count++;
        return count;
    }
    // may be we hav't PROCESS_QUERY_INFORMATION access right
    SYSTEM_INFO sysinfo;
    GetSystemInfo( &sysinfo );
    return sysinfo.dwNumberOfProcessors;
}