To set the affinity of CPUs using C#

Question

I have created a window application in C#.Now I want to set the CPU affinity for this application.I may have 2 processors,4 processors,8 processors or may be more than 8 processors.

I want to set the cpu affinity using input from interface.

How can i achieve this? How can it is possible to set the affinity using Environment.ProcessorCount?

Answer 1

Try this:

Process.GetCurrentProcess().ProcessorAffinity = (System.IntPtr)2;

Here's more about it.

ProcessorAffinity represents each processor as a bit. Bit 0 represents processor one, bit 1 represents processor two, and so on. The following table shows a subset of the possible ProcessorAffinity for a four-processor system.

Property value (in hexadecimal)  Valid processors

0x0001                           1
0x0002                           2
0x0003                           1 or 2
0x0004                           3
0x0005                           1 or 3
0x0007                           1, 2, or 3
0x000F                           1, 2, 3, or 4

Here's a small sample program:

//TODO: manage exceptions
class Program
{
    static void Main(string[] args)
    {
        Console.WriteLine("Total # of processors: {0}", Environment.ProcessorCount);
        Console.WriteLine("Current processor affinity: {0}", Process.GetCurrentProcess().ProcessorAffinity);
        Console.WriteLine("*********************************");
        Console.WriteLine("Insert your selected processors, separated by comma (first CPU index is 1):");
        var input = Console.ReadLine();
        Console.WriteLine("*********************************");
        var usedProcessors = input.Split(',');

        //TODO: validate input
        int newAffinity = 0;
        foreach (var item in usedProcessors)
        {
            newAffinity = newAffinity | int.Parse(item);
            Console.WriteLine("Processor #{0} was selected for affinity.", item);
        }
        Process.GetCurrentProcess().ProcessorAffinity = (System.IntPtr)newAffinity;
        Console.WriteLine("*********************************");
        Console.WriteLine("Current processor affinity is {0}", Process.GetCurrentProcess().ProcessorAffinity);
    }
}

Answer 2

The provided sample program by Alex Filipovivi seems incorrect, in that it ORs processor numbers into newAffinity without first converting them into a set bit. So if you input 3,4 to this program, you get an affinity mask of 7, which is cores 1, 2, and 3! The mask should be set to 12 (hex 0xC, binary 1100, which has bits 2 and 3 set, if bit 0 is the least significant bit).

Replacing

newAffinity = NewAffinity | int.Parse(item);

with

newAffinity = newAffinity | (1 << int.Parse(item)-1);

Is one reasonable way to do that.