Task Parallel is unstable, using 100% CPU at times

Question

I\'m currently testing out Parallel for C#. Generally it works fine, and using parallel is faster than the normal foreach loops. However, at times (like 1 out of 5 times), my

Answer 1

I had a similar problem. I am using octa-core I5 processor with 16GB RAM, Parallel.Foreach was hitting 100% CPU, after making a minor code change CPU utilization came down to under 20%. This is my sample code.

static void Main(string[] args)
    {
        List values = Enumerable.Range(1, 100000000).ToList();
        long sum = 0;

        Parallel.ForEach(values,
            new ParallelOptions { MaxDegreeOfParallelism = Environment.ProcessorCount },
            x =>
            AddValues(x, ref sum)
            );
        Console.WriteLine(sum);
    }

    private static long AddValues(int x, ref long sum)
    {
        PerformanceCounter cpuCounter = new PerformanceCounter("Processor", "% Processor Time", "_Total");
        CheckCPUUsageAndSleepThread(cpuCounter);

        int y = x * 5;            
        for (int i=0;i 80) //Check if CPU utilization crosses 80%  
        {
            Thread.Sleep(1);
        }
    }

When CPU utilization crosses 80% I pause for 1 millisecond. This solved my problem. If you have a situation where you need to go with parallel.foreach loop, You could try calling this function, else you can try above solutions

CheckCPUUsageAndSleepThread()

I hope it helps.

PS: To simulate 100% CPU usage comment Thread.Sleep(1)