ArrayPool

using System;
using System.Threading;
using System.Buffers;

class Program
{
#if false
    static byte[] AcquireBuffer()
    {
        return new byte[4096];
    }

    static void ReleaseBuffer(byte[] b)
    {
    }
#endif

#if false
    [ThreadStatic]
    static byte[] manualPool;

    static byte[] AcquireBuffer()
    {
        byte[] ret = manualPool;
        manualPool = null;

        if (ret == null)
            ret = new byte[4096];

        return ret;
    }

    static void ReleaseBuffer(byte[] b)
    {
        manualPool = b;
    }
#endif

#if false
    static byte[] AcquireBuffer()
    {
        return ArrayPool<byte>.Shared.Rent(4096);
    }

    static void ReleaseBuffer(byte[] b)
    {
        ArrayPool<byte>.Shared.Return(b);
    }
#endif

    static int Workitem()
    {
        byte[] b = AcquireBuffer();

        for (int i = 0; i < 4096; i++)
            b[i] = (byte)i;

        int sum = 0;
        for (int i = 0; i < 4096; i++)
            sum += b[i];

        ReleaseBuffer(b);

        return sum;
    }

    static void Work()
    {
        for (int i = 0; i < 1000000; i++)
        {
            Workitem();
        }
    }

    static void Main(string[] args)
    {
        int start = Environment.TickCount;

        Thread[] threads = new Thread[Environment.ProcessorCount];

        for (int i = 0; i < threads.Length; i++)
            (threads[i] = new Thread(Work)).Start();

        for (int i = 0; i < threads.Length; i++)
            threads[i].Join();

        int end = Environment.TickCount;
        Console.WriteLine("Time: " + (end - start));
    }
}