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
