ネイティブからネイティブへのコピー速度比較

NativeMem2NativeMem.cs

using System;
using System.Diagnostics;
using System.IO;
using System.Linq;
using System.Runtime.InteropServices;

namespace ConsoleApp75
{
    class Program
    {
        [DllImport("Kernel32.dll", EntryPoint = "RtlMoveMemory")]
        private static extern void CopyMemory(IntPtr Destination, IntPtr Source, [MarshalAs(UnmanagedType.U4)] int Length);

        static unsafe void Main(string[] args)
        {
            const int size = 1073741824;
            const int count = 100;

            IntPtr ptr = Marshal.AllocCoTaskMem(size);
            IntPtr ptr2 = Marshal.AllocCoTaskMem(size);
            byte[] bytes = Enumerable.Repeat((byte)128, size).ToArray();

            using (MemoryStream streamSrc = new MemoryStream(bytes))
            using (UnmanagedMemoryStream streamDst = new UnmanagedMemoryStream((byte*)ptr, size, size, FileAccess.Write))
                streamSrc.CopyTo(streamDst);

            Console.WriteLine("Performing tests on copying {0} megabytes of memory.", size / (double)1024 / 1024);

            GC.Collect();

            Stopwatch watch = new Stopwatch();
            // make sure methods are JIT’d (they probably are, since there
            // should be native images of the standard library, but just to be safe..)

            watch.Reset();
            watch.Start();

            watch.Stop();

            double averageTime = 0;

            {
                watch.Reset();
                watch.Start();
                {
                    using (UnmanagedMemoryStream streamSrc = new UnmanagedMemoryStream((byte*)ptr, size, size, FileAccess.Read))
                    using (UnmanagedMemoryStream streamDst = new UnmanagedMemoryStream((byte*)ptr2, size, size, FileAccess.Write))
                    {
                        for (int i = 0; i < count; i++)
                        {
                            streamSrc.Position = 0;
                            streamDst.Position = 0;
                            streamSrc.CopyTo(streamDst);
                        }
                    }
                }
                watch.Stop();

                averageTime = watch.ElapsedMilliseconds / (double)count;
                Console.WriteLine("Average time for Stream is {0} ms.", averageTime);
            }

            {
                watch.Reset();
                watch.Start();
                for (int i = 0; i < count; i++)
                {
                    CopyMemory(ptr2, ptr, size);
                }

                watch.Stop();

                averageTime = watch.ElapsedMilliseconds / (double)count;
                Console.WriteLine("Average time for API is {0} ms.", averageTime);
            }

            {
                watch.Reset();
                watch.Start();
                for (int i = 0; i < count; i++)
                {
                    Buffer.MemoryCopy((void*)ptr, (void*)ptr2, size, size);
                }

                watch.Stop();

                averageTime = watch.ElapsedMilliseconds / (double)count;
                Console.WriteLine("Average time for Buffer is {0} ms.", averageTime);
            }

            {
                watch.Reset();
                watch.Start();

                int* src = (int*)ptr;
                int* dest = (int*)ptr2;
                for (int j = 0; j < count; j++)
                {
                    for (int i = 0; i < size / sizeof(int); i++)
                    {
                        dest[i] = src[i];
                    }
                }

                watch.Stop();
                averageTime = watch.ElapsedMilliseconds / (double)count;
                Console.WriteLine("Average time int copy is {0} ms.", averageTime);
            }

            Marshal.FreeHGlobal(ptr);
            Marshal.FreeHGlobal(ptr2);

            Console.WriteLine("Done.");
            Console.ReadKey();
        }
    }
}