2D array vs 1D array performance in C#

Unity Engine
,
1

Is there performance difference between using 2D and 1D arrays?

I remember someone saying 1D arrays had better performance, but am not sure if it was true.

Has anyone done any tests, or know anything?

2

It’s true. 1D array > jagged array > 2D array.

–Eric

3

any stats on actual performance increase?

4

A 1D array is only a little faster than a jagged array, but both are somewhat faster than a 2D array. It’s easy enough to run a few benchmarks to see for yourself. Not worth worrying about unless you’re constantly accessing the array a lot, though; a 2D array is the simplest method for using a multi-D array so you should use that unless there’s a good reason otherwise.

–Eric

5

It depends on how many operations you are performing. In the below example, I’m setting the values of the array 2500 times. Size of the array is (1000 * 1000 * 3). The 1D array took 40 seconds and the 3D array took 1:39 mins.

var startTime = DateTime.Now;
Test1D(new byte[1000 * 1000 * 3]);
Console.WriteLine("Total Time taken 1d = " + (DateTime.Now - startTime));

startTime = DateTime.Now;
Test3D(new byte[1000,1000,3], 1000, 1000);
Console.WriteLine("Total Time taken 3D = " + (DateTime.Now - startTime));

public static void Test1D(byte[ ] array)
{
for (int c = 0; c < 2500; c++)
{
for (int i = 0; i < array.Length; i++)
{
array = 10;
}
}
}
public static void Test3D(byte[,] array, int w, int h)
{
for (int c = 0; c < 2500; c++)
{
for (int i = 0; i < h; i++)
{
for (int j = 0; j < w; j++)
{
array[i, j, 0] = 10;
array[i, j, 1] = 10;
array[i, j, 2] = 10;
}
}
}
}

6

Please use code tags when posting code.

–Eric