CODEWITHSUNDEEP
c#parallel-processingtask-parallel-library
Harry Boy
Harry Boy

Reputation: 4745

How to split work over multiple cores/processors

I want to create a small test that carries out some calculations to see how fast a processor will finish it in. For example I want to get the CPU info of a machine and then run a test like so:

public static double SumRootN(int root)
    {
        double result = 0;
        for (int i = 1; i < 10000000; i++)
        {
            result += Math.Exp(Math.Log(i) / root);
        }
        return result;
    }

    private void buttonStart_Click(object sender, EventArgs e)
    {
        labelPhysicalProcessors.Text = "";
        labelProcessorName.Text = "";
        labelLogicalProcessors.Text = "";
        labelCores.Text = "";

        this.Cursor = Cursors.WaitCursor;

        string physicalProcessors = String.Empty;
        string processorName = String.Empty;
        string logicalProcessors = String.Empty;
        string coreCount = String.Empty;

        foreach (var item in new System.Management.ManagementObjectSearcher("Select * from Win32_ComputerSystem").Get())
        {
            physicalProcessors = item["NumberOfProcessors"].ToString();
            logicalProcessors = item["NumberOfLogicalProcessors"].ToString();
        }


        foreach (var item in new System.Management.ManagementObjectSearcher("Select * from Win32_Processor").Get())
        {
            coreCount = item["NumberOfCores"].ToString();
            processorName = item["Name"].ToString();
        }

        labelPhysicalProcessors.Text = physicalProcessors;
        labelProcessorName.Text = processorName;
        labelLogicalProcessors.Text = logicalProcessors;
        labelCores.Text = coreCount;

        var watch = Stopwatch.StartNew();


        Parallel.For(2, 20, (i) =>
        {
            var result = SumRootN(i);
            //Console.WriteLine("root {0} : {1} ", i, result);
        });


        labelTime.Text = watch.ElapsedMilliseconds.ToString() + " ms";


        this.Cursor = Cursors.Arrow;

    }

This produces: enter image description here

I want to take advantage of the number of cores and logical processors on the CPU. How can I do this in C# i.e. if a machie has more cores then I want to split the work up onto each core so a machine with more cores and logical procesors will run the test faster.

Upvotes: 1

Views: 1602

Answers (1)

usr
usr

Reputation: 171178

If you're building a benchmark you should control threading tightly. Start N threads manually where N is Environment.ProcessorCount. Don't even use the Task facility because it gives you less fairness guarantees.

You might want to increase the thread priority to reduce context switching induced timing jitter.

Upvotes: 1

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