How to get number of CPU's logical cores/threads in C#?

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How I can get number of logical cores in CPU?

I need this to determine how many threads I should run in my application.

Peckham answered 22/10, 2012 at 16:35 Comment(2)

It's OS-dependent, so what OS? – Tinatinamou 22/10, 2012 at 16:38

Any Windows that supports .net 3.5 – Peckham 22/10, 2012 at 16:42

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You can get number of logical processors through the Environment class
number of 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);

number of logical processors

foreach (var item in new System.Management.ManagementObjectSearcher("Select * from Win32_ComputerSystem").Get())
{
    Console.WriteLine("Number Of Logical Processors: {0}", item["NumberOfLogicalProcessors"]);
}

Environment.ProcessorCount

 using System;

 class Sample 
 {
     public static void Main() 
     {
        Console.WriteLine("The number of processors on this computer is {0}.", 
           Environment.ProcessorCount);
     }
 }

go through this link http://msdn.microsoft.com/en-us/library/system.environment.processorcount.aspx

Paramagnet answered 22/10, 2012 at 16:41 Comment(5)

I have no ManagementObjectSearcher object in System.Management. Why? – Peckham 22/10, 2012 at 16:47

@Kamil: check Assembly: System.Management (in System.Management.dll) – Paramagnet 22/10, 2012 at 16:49

@Kamil: check it is in System.ComponentModel.Component – Paramagnet 22/10, 2012 at 16:52

I tried Environment.ProcessorCount, looks OK, i have 2 cores detected on Core Duo T2500 CPU. I have to try this on quad core xeon with HT. – Peckham 22/10, 2012 at 16:57

I found and added reference to that dll. It also works, but much slower than Environment.ProcessorCount. What is the difference? I know why WMI technique works slower, but can results differ? Will Win32_ComputerSystem work on Windows 64? – Peckham 22/10, 2012 at 17:1

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Use the Environment.ProcessorCount property, it returns the number of logical cores.

Endanger answered 22/10, 2012 at 16:39 Comment(1)

Thanks @MikeT, but i had to accept answer that took author little more time. Your answer is satisfying too. – Peckham 22/10, 2012 at 17:11

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