How to Determine the Number of Physical, Logical, and Available CPU Cores in .NET/C#?

Use .NET/C# to detect the number of CPU cores

With the increasing popularity of multi-processing, it is crucial to determine the number of CPU cores for optimal performance. In .NET/C#, there are several ways to access this information:

Physical Processor

The number of physical processors can be retrieved using the following code:

foreach (var item in new System.Management.ManagementObjectSearcher("Select * from Win32_ComputerSystem").Get())
{
    Console.WriteLine("物理处理器数量：{0}", item["NumberOfProcessors"]);
}

Kernel

To determine the number of cores, execute the following code:

int coreCount = 0;
foreach (var item in new System.Management.ManagementObjectSearcher("Select * from Win32_Processor").Get())
{
    coreCount += int.Parse(item["NumberOfCores"].ToString());
}
Console.WriteLine("内核数量：{0}", coreCount);

Logical Processor

The number of logical processors (often called hyperthreads) can be obtained using either of the following codes:

Console.WriteLine("逻辑处理器数量：{0}", Environment.ProcessorCount);

foreach (var item in new System.Management.ManagementObjectSearcher("Select * from Win32_ComputerSystem").Get())
{
    Console.WriteLine("逻辑处理器数量：{0}", item["NumberOfLogicalProcessors"]);
}

Excluded Processors

In some Windows configurations, specific processors may be excluded from detection. To do this you can use the Windows API call found in setupapi.dll:

static void Main(string[] args)
{
    int deviceCount = 0;
    IntPtr deviceList = IntPtr.Zero;

    try
    {
        deviceList = SetupDiGetClassDevs(ref processorGuid, "ACPI", IntPtr.Zero, (int)DIGCF.PRESENT);
        for (int deviceNumber = 0; ; deviceNumber++)
        {
            SP_DEVINFO_DATA deviceInfo = new SP_DEVINFO_DATA();
            deviceInfo.cbSize = Marshal.SizeOf(deviceInfo);

            if (!SetupDiEnumDeviceInfo(deviceList, deviceNumber, ref deviceInfo))
            {
                deviceCount = deviceNumber;
                break;
            }
        }
    }
    finally
    {
        if (deviceList != IntPtr.Zero) { SetupDiDestroyDeviceInfoList(deviceList); }
    }
    Console.WriteLine("内核数量：{0}", deviceCount);
}

[DllImport("setupapi.dll", SetLastError = true)]
private static extern IntPtr SetupDiGetClassDevs(ref Guid ClassGuid,
    [MarshalAs(UnmanagedType.LPStr)]String enumerator,
    IntPtr hwndParent,
    Int32 Flags);

[DllImport("setupapi.dll", SetLastError = true)]
private static extern Int32 SetupDiDestroyDeviceInfoList(IntPtr DeviceInfoSet);

[DllImport("setupapi.dll", SetLastError = true)]
private static extern bool SetupDiEnumDeviceInfo(IntPtr DeviceInfoSet,
    Int32 MemberIndex,
    ref SP_DEVINFO_DATA DeviceInterfaceData);

[StructLayout(LayoutKind.Sequential)]
private struct SP_DEVINFO_DATA
{
    public int cbSize;
    public Guid ClassGuid;
    public uint DevInst;
    public IntPtr Reserved;
}

private enum DIGCF
{
    DEFAULT = 0x1,
    PRESENT = 0x2,
    ALLCLASSES = 0x4,
    PROFILE = 0x8,
    DEVICEINTERFACE = 0x10,
}

private static readonly Guid processorGuid = new Guid("{4d36e968-e325-11ce-bfc1-08002be10318}");

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