Does Array.Copy work with multidimensional arrays?

Question

This code works fine:

var newArray = new Rectangle[newHeight, newWidth];

for (int x = 0; x < newWidth; x++)
    for (int y = 0; y < newHeight; y++)
           


        

Answer 1

I had a need to consume data from a buffer and copy off to a large holding array before the next interrupt hit. Copying in a loop wasn't an option; far too slow. I didn't need the multidimensional structure of the combined data until all of the copying was done, this meant I could Buffer.BlockCopy() to a single dimension array, then copy again onto a multidimensional array to obtain the required structure. Here's some code (run it in a console) that will demonstrate the technique as well as the performance.

static class Program
{
    [STAThread]
    static void Main()
    {
        Stopwatch watch = new Stopwatch();

        const int width = 2;
        const int depth = 10 * 1000000;

        //  Create a large array of data
        Random r = new Random(100);
        int[,] data = new int[width, depth];
        for(int i = 0; i < width; i++)
        {
            for(int j = 0; j < depth; j++)
            {
                data[i, j] = r.Next();
            }
        }

        //  Block copy to a single dimension array
        watch.Start();
        int[] buffer = new int[width * depth];
        Buffer.BlockCopy(data, 0, buffer, 0, data.Length * sizeof(int));
        watch.Stop();
        Console.WriteLine("BlockCopy to flat array took {0}", watch.ElapsedMilliseconds);

        //  Block copy to multidimensional array
        int[,] data2 = new int[width, depth];
        watch.Start();
        Buffer.BlockCopy(buffer, 0, data2, 0,buffer.Length * sizeof(int));
        watch.Stop();
        Console.WriteLine("BlockCopy to 2 dimensional array took {0}", watch.ElapsedMilliseconds);


        //  Now try a loop based copy - eck!
        data2 = new int[width, depth];
        watch.Start();
        for (int i = 0; i < width; i++)
        {
            for (int j = 0; j < depth; j++)
            {
                data2[i, j] = data[i, j];
            }
        }
        watch.Stop();
        Console.WriteLine("Loop-copy to 2 dimensional array took {0} ms", watch.ElapsedMilliseconds);
    }
}

Output:

BlockCopy to flat array took 14 ms
BlockCopy to 2 dimensional array took 28 ms
Loop-copy to 2 dimensional array took 149 ms