How Can I Determine the Number of CPU Cores in My .NET/C# Application?

Determine the number of CPU cores in .NET/C#

Understanding the number of available CPU cores is critical to optimizing resource utilization for .NET/C# applications. This article explores several ways to retrieve this information, allowing developers to make informed decisions about multithreading and performance optimization.

Physical Processors, Cores and Logical Processors

It is important to differentiate between the number of physical processors, cores, and logical processors. A physical processor represents the actual hardware unit, while a core is a single execution unit within the processor. A logical processor is a virtualized representation of a core, allowing the operating system to schedule threads more efficiently by presenting them as separate entities.

Retrieve the number of cores

In .NET/C#, there are several ways to retrieve the number of CPU cores.

Logical processor (Environment class)

The Environment class provides access to the number of logical processors:

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

Core (WMI)

Using WMI (Windows Management Instrumentation) you can retrieve the 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("核心数量：{0}", coreCount);

Physical Processor (WMI)

In .NET Core you can get the number of physical processors using WMI:

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"]);
}

Excluded Processors in Windows (Windows API)

Windows API call in setupapi.dll allows discovery of excluded processors in Windows:

static void Main(string[] args)
{
    int deviceCount = 0;
    IntPtr deviceList = IntPtr.Zero;
    // 处理器类ID的GUID
    Guid processorGuid = new Guid("{50127dc3-0f36-415e-a6cc-4cb3be910b65}");
    ...
    Console.WriteLine("核心数量：{0}", deviceCount);
}

Summary

This article demonstrates several methods of retrieving the number of CPU cores in .NET/C#. By understanding these techniques, developers can optimize resource utilization, balance thread workloads, and improve application performance.

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