How to find the Number of CPU Cores via NET C

Question

Is there a way via  NET C  to find out the number of CPU cores   PS This is a straight code question  not a  Should I use multi-threading   question   -

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It s rather interesting to see how  NET get this internally to say the least    It s as  simple  as below   namespace System Threading       using System      using System Runtime CompilerServices       internal static class PlatformHelper               private const int PROCESSOR COUNT REFRESH INTERVAL MS   0x7530          private static volatile int s lastProcessorCountRefreshTicks          private static volatile int s processorCount           internal static bool IsSingleProcessor                       get                               return  ProcessorCount    1                                    internal static int ProcessorCount                       get                               int tickCount   Environment TickCount                  int num2   s processorCount                  if   num2    0       tickCount - s lastProcessorCountRefreshTicks   gt   0x7530                                         s processorCount   num2   Environment ProcessorCount                      s lastProcessorCountRefreshTicks   tickCount                                    return num2

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From  NET Framework source  You can also get it with PInvoke on Kernel32 dll  The following code is coming more or less from SystemInfo cs from System Web source located here    StructLayout LayoutKind Sequential  Pack   1   public struct SYSTEM INFO     public ushort wProcessorArchitecture    public ushort wReserved    public uint dwPageSize    public IntPtr lpMinimumApplicationAddress    public IntPtr lpMaximumApplicationAddress    public IntPtr dwActiveProcessorMask    public uint dwNumberOfProcessors    public uint dwProcessorType    public uint dwAllocationGranularity    public ushort wProcessorLevel    public ushort wProcessorRevision     internal static class SystemInfo        static int  trueNumberOfProcessors      internal static readonly IntPtr INVALID HANDLE VALUE   new IntPtr -1             DllImport  kernel32 dll   CharSet   CharSet Unicode       internal static extern void GetSystemInfo out SYSTEM INFO si         DllImport  kernel32 dll        internal static extern int GetProcessAffinityMask IntPtr handle  out IntPtr processAffinityMask  out IntPtr systemAffinityMask        internal static int GetNumProcessCPUs               if  SystemInfo  trueNumberOfProcessors    0                  SYSTEM INFO si          GetSystemInfo out si           if   int  si dwNumberOfProcessors    1                      SystemInfo  trueNumberOfProcessors   1                    else                     IntPtr processAffinityMask            IntPtr systemAffinityMask            if  GetProcessAffinityMask INVALID HANDLE VALUE  out processAffinityMask  out systemAffinityMask     0                          SystemInfo  trueNumberOfProcessors   1                        else                         int num1   0              if  IntPtr Size    4                              uint num2    uint   int  processAffinityMask                while   int  num2    0                                  if    int  num2  amp  1     1                      num1                  num2  gt  gt   1                                            else                             ulong num2    ulong   long  processAffinityMask                while   long  num2    0L                                  if    long  num2  amp  1L     1L                      num1                  num2  gt  gt   1                                            SystemInfo  trueNumberOfProcessors   num1                                      return SystemInfo  trueNumberOfProcessors

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The following program prints the logical and physical cores of a windows machine    define STRICT  include  stdafx h   include  lt windows h gt   include  lt stdio h gt   include  lt omp h gt   template lt typename T gt  T  AdvanceBytes T  p  SIZE T cb     return reinterpret cast lt T  gt  reinterpret cast lt BYTE   gt  p    cb      class EnumLogicalProcessorInformation   public   EnumLogicalProcessorInformation LOGICAL PROCESSOR RELATIONSHIP Relationship      m pinfoBase nullptr   m pinfoCurrent nullptr   m cbRemaining 0       DWORD cb   0    if  GetLogicalProcessorInformationEx Relationship                                         nullptr   amp cb   return    if  GetLastError      ERROR INSUFFICIENT BUFFER  return     m pinfoBase      reinterpret cast lt SYSTEM LOGICAL PROCESSOR INFORMATION EX   gt                                        LocalAlloc LMEM FIXED  cb      if   m pinfoBase  return     if   GetLogicalProcessorInformationEx Relationship                                           m pinfoBase   amp cb   return     m pinfoCurrent   m pinfoBase    m cbRemaining   cb        EnumLogicalProcessorInformation     LocalFree m pinfoBase       void MoveNext        if  m pinfoCurrent       m cbRemaining -  m pinfoCurrent- gt Size     if  m cbRemaining        m pinfoCurrent   AdvanceBytes m pinfoCurrent                                    m pinfoCurrent- gt Size        else       m pinfoCurrent   nullptr                SYSTEM LOGICAL PROCESSOR INFORMATION EX  Current                                              return m pinfoCurrent    private   SYSTEM LOGICAL PROCESSOR INFORMATION EX  m pinfoBase   SYSTEM LOGICAL PROCESSOR INFORMATION EX  m pinfoCurrent   DWORD m cbRemaining       int   cdecl main int argc  char   argv      int numLogicalCore   0    int numPhysicalCore   0     for  EnumLogicalProcessorInformation enumInfo RelationProcessorCore         auto pinfo   enumInfo Current    enumInfo MoveNext               int numThreadPerCore    pinfo- gt Processor Flags    LTP PC SMT    2   1           std  cout  lt  lt   thread per core    lt  lt  numThreadPerCore  lt  lt  std  endl        numLogicalCore    numThreadPerCore        numPhysicalCore    1         printf   Number of physical core    d   Number of Logical core    d  n   numPhysicalCore  numLogicalCore      char c   getchar       just to wait on to see the results in the command prompt     return 0        I tested with Intel Xeon four cores with hyper threading and here is the result Number of physical core   4   Number of Logical core   8

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I was looking for the same thing but I don t want to install any nuget or servicepack  so I found this solution  it is pretty simple and straight forward   using this discussion  I thought it would be so easy to run that WMIC command and get that value  here is the C  code  You only need to use System Management namespace  and couple more standard namespaces for process and so on    string fileName   Path Combine Environment SystemDirectory   wbem    wmic exe    string arguments     cpu get NumberOfCores    Process process   new Process       StartInfo                 FileName   fileName          Arguments   arguments          UseShellExecute   false          CreateNoWindow   true          RedirectStandardOutput   true          RedirectStandardError   true           process Start     StreamReader output   process StandardOutput  Console WriteLine output ReadToEnd       process WaitForExit    int exitCode   process ExitCode  process Close

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Environment ProcessorCount    Documentation

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The the easyest way   Environment ProcessorCount Exemple from Environment ProcessorCount Property  using System   class Sample        public static void Main                  Console WriteLine  The number of processors                  on this computer is  0                  Environment ProcessorCount

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Environment ProcessorCount should give you the number of cores on the local machine

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WMI queries are slow  so try to Select only the desired members instead of using Select      The following query takes 3 4s   foreach  var item in new System Management ManagementObjectSearcher  Select   from Win32 Processor   Get      While this one takes 0 122s   foreach  var item in new System Management ManagementObjectSearcher  Select NumberOfCores from Win32 Processor   Get

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There are many answers here already  but some have heavy upvotes and are incorrect  The  NET Environment ProcessorCount WILL return incorrect values and can fail critically if your system WMI is configured incorrectly  If you want a RELIABLE way to count the cores  the only way is Win32 API  Here is a C   snippet   include  lt Windows h gt   include  lt vector gt   int num physical cores         static int num cores                    DWORD bytes   0          GetLogicalProcessorInformation nullptr   amp bytes           std  vector lt SYSTEM LOGICAL PROCESSOR INFORMATION gt  coreInfo bytes   sizeof SYSTEM LOGICAL PROCESSOR INFORMATION            GetLogicalProcessorInformation coreInfo data     amp bytes            int cores   0          for  auto amp  info   coreInfo                        if  info Relationship    RelationProcessorCore                    cores                    return cores  gt  0   cores   1               return num cores     And since this is a  NET C  Question  here s the ported version   StructLayout LayoutKind Sequential   struct CACHE DESCRIPTOR       public byte Level      public byte Associativity      public ushort LineSize      public uint Size      public uint Type      StructLayout LayoutKind Explicit   struct SYSTEM LOGICAL PROCESSOR INFORMATION UNION        FieldOffset 0   public byte ProcessorCore       FieldOffset 0   public uint NumaNode       FieldOffset 0   public CACHE DESCRIPTOR Cache       FieldOffset 0   private UInt64 Reserved1       FieldOffset 8   private UInt64 Reserved2     public enum LOGICAL PROCESSOR RELATIONSHIP       RelationProcessorCore      RelationNumaNode      RelationCache      RelationProcessorPackage      RelationGroup      RelationAll   0xffff    struct SYSTEM LOGICAL PROCESSOR INFORMATION       public UIntPtr ProcessorMask      public LOGICAL PROCESSOR RELATIONSHIP Relationship      public SYSTEM LOGICAL PROCESSOR INFORMATION UNION ProcessorInformation      DllImport  quot kernel32 dll quot    static extern unsafe bool GetLogicalProcessorInformation SYSTEM LOGICAL PROCESSOR INFORMATION  buffer  out int bufferSize    static unsafe int GetProcessorCoreCount         GetLogicalProcessorInformation null  out int bufferSize       int numEntries   bufferSize   sizeof SYSTEM LOGICAL PROCESSOR INFORMATION       var coreInfo   new SYSTEM LOGICAL PROCESSOR INFORMATION numEntries        fixed  SYSTEM LOGICAL PROCESSOR INFORMATION  pCoreInfo   coreInfo                GetLogicalProcessorInformation pCoreInfo  out bufferSize           int cores   0          for  int i   0  i  lt  numEntries    i                        ref SYSTEM LOGICAL PROCESSOR INFORMATION info   ref pCoreInfo i               if  info Relationship    LOGICAL PROCESSOR RELATIONSHIP RelationProcessorCore                    cores                    return cores  gt  0   cores   1           public static readonly int NumPhysicalCores   GetProcessorCoreCount

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One option would be to read the data from the registry  MSDN Article On The Topic  http   msdn microsoft com en-us library microsoft win32 registry localmachine v vs 71  aspx   The processors  I believe can be located here  HKEY LOCAL MACHINE HARDWARE DESCRIPTION System CentralProcessor      private void determineNumberOfProcessCores                 RegistryKey rk   Registry LocalMachine          String   subKeys   rk OpenSubKey  HARDWARE   OpenSubKey  DESCRIPTION   OpenSubKey  System   OpenSubKey  CentralProcessor   GetSubKeyNames             textBox1 Text    Total number of cores     subKeys Length ToString            I am reasonably sure the registry entry will be there on most systems   Though I would throw my  0 02 in

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There are several different pieces of information relating to processors that you could get     Number of physical processors Number of cores Number of logical processors    These can all be different  in the case of a machine with 2 dual-core hyper-threading-enabled processors  there are 2 physical processors  4 cores  and 8 logical processors   The number of logical processors is available through the Environment class  but the other information is only available through WMI  and you may have to install some hotfixes or service packs to get it on some systems    Make sure to add a reference in your project to System Management dll In  NET Core  this is available  for Windows only  as a NuGet package   Physical Processors   foreach  var item in new System Management ManagementObjectSearcher  Select   from Win32 ComputerSystem   Get          Console WriteLine  Number Of Physical Processors   0     item  NumberOfProcessors         Cores   int coreCount   0  foreach  var item in new System Management ManagementObjectSearcher  Select   from Win32 Processor   Get          coreCount    int Parse item  NumberOfCores   ToString       Console WriteLine  Number Of Cores   0    coreCount     Logical Processors   Console WriteLine  Number Of Logical Processors   0    Environment ProcessorCount     OR  foreach  var item in new System Management ManagementObjectSearcher  Select   from Win32 ComputerSystem   Get          Console WriteLine  Number Of Logical Processors   0    item  NumberOfLogicalProcessors         Processors excluded from Windows   You can also use Windows API calls in setupapi dll to discover processors that have been excluded from Windows  e g  through boot settings  and aren t detectable using the above means  The code below gives the total number of logical processors  I haven t been able to figure out how to differentiate physical from logical processors  that exist  including those that have been excluded from Windows   static void Main string   args        int deviceCount   0      IntPtr deviceList   IntPtr Zero         GUID for processor classid     Guid processorGuid   new Guid   50127dc3-0f36-415e-a6cc-4cb3be910b65          try                  get a list of all processor devices         deviceList   SetupDiGetClassDevs ref processorGuid   ACPI   IntPtr Zero   int DIGCF PRESENT              attempt to process each item in the list         for  int deviceNumber   0    deviceNumber                          SP DEVINFO DATA deviceInfo   new SP DEVINFO DATA                deviceInfo cbSize   Marshal SizeOf deviceInfo                   attempt to read the device info from the list  if this fails  we re at the end of the list             if   SetupDiEnumDeviceInfo deviceList  deviceNumber  ref deviceInfo                                 deviceCount   deviceNumber                  break                                    finally               if  deviceList    IntPtr Zero    SetupDiDestroyDeviceInfoList deviceList               Console WriteLine  Number of cores   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

[c#] How to find the Number of CPU Cores via .NET/C#?

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