How to split an array into chunks of specific size? [closed]

Answer 1

You can use List.GetRange:

for(var i = 0; i < source.Count; i += chunkSize)
{
    List items = source.GetRange(i, Math.Min(chunkSize, source.Count - i));
}

Although not at fast as Array.Copy, I think it looks cleaner:

var list = Enumerable.Range(0, 723748).ToList();

var stopwatch = new Stopwatch();

for (int n = 0; n < 5; n++)
{
    stopwatch.Reset();
    stopwatch.Start();
    for(int i = 0; i < list.Count; i += 100)
    {
        List c = list.GetRange(i, Math.Min(100, list.Count - i));
    }
    stopwatch.Stop();
    Console.WriteLine("List.GetRange: " + stopwatch.ElapsedMilliseconds.ToString());

    stopwatch.Reset();
    stopwatch.Start();
    for (int i = 0; i < list.Count; i += 100)
    {
        List c = list.Skip(i).Take(100).ToList();
    }
    stopwatch.Stop();
    Console.WriteLine("Skip/Take: " + stopwatch.ElapsedMilliseconds.ToString());

    stopwatch.Reset();
    stopwatch.Start();
    var test = list.ToArray();
    for (int i = 0; i < list.Count; i += 100)
    {
        int length = Math.Min(100, list.Count - i);
        int[] c = new int[length];
        Array.Copy(test, i, c, 0, length);
    }
    stopwatch.Stop();
    Console.WriteLine("Array.Copy: " + stopwatch.ElapsedMilliseconds.ToString());

    stopwatch.Reset();
    stopwatch.Start();
    List> chunks = list
        .Select((s, i) => new { Value = s, Index = i })
        .GroupBy(x => x.Index / 100)
        .Select(grp => grp.Select(x => x.Value).ToList())
        .ToList();
    stopwatch.Stop();
    Console.WriteLine("LINQ: " + stopwatch.ElapsedMilliseconds.ToString());
}

Results in milliseconds:

List.GetRange: 1
Skip/Take: 9820
Array.Copy: 1
LINQ: 161

List.GetRange: 9
Skip/Take: 9237
Array.Copy: 1
LINQ: 148

List.GetRange: 5
Skip/Take: 9470
Array.Copy: 1
LINQ: 186

List.GetRange: 0
Skip/Take: 9498
Array.Copy: 1
LINQ: 110

List.GetRange: 8
Skip/Take: 9717
Array.Copy: 1
LINQ: 148