A.md

100 000 records

Creating test data (100000 records)... DONE
    Elapsed....: 00:00:00.0340276
    # per µs...: 2,94
    µs per #...: 0,34

Creating subset (1000 records... DONE
    Elapsed....: 00:00:00.0003953
    # per µs...: 2,53
    µs per #...: 0,40

TEST 1: Filtering with subset as Array... DONE
    Elapsed....: 00:00:00.4449301
    # per µs...: 0,22
    µs per #...: 4,45

TEST 2: Filtering with subset as List... DONE
    Elapsed....: 00:00:00.7225637
    # per µs...: 0,14
    µs per #...: 7,23

TEST 3: Filtering with subset as Dictionary... DONE
    Elapsed....: 00:00:00.0027382
    # per µs...: 36,52
    µs per #...: 0,03

TEST 4: Filtering with subset as HashSet... DONE
    Elapsed....: 00:00:00.0029626
    # per µs...: 33,75
    µs per #...: 0,03

100 records

Creating test data (100 records)... DONE
    Elapsed....: 00:00:00.0002003
    # per µs...: 0,50
    µs per #...: 2,00

Creating subset (1 records... DONE
    Elapsed....: 00:00:00.0001631
    # per µs...: 0,01
    µs per #...: 163,10

TEST 1: Filtering with subset as Array... DONE
    Elapsed....: 00:00:00.0002622
    # per µs...: 0,38
    µs per #...: 2,62

TEST 2: Filtering with subset as List... DONE
    Elapsed....: 00:00:00.0002215
    # per µs...: 0,45
    µs per #...: 2,22

TEST 3: Filtering with subset as Dictionary... DONE
    Elapsed....: 00:00:00.0002141
    # per µs...: 0,47
    µs per #...: 2,14

TEST 4: Filtering with subset as HashSet... DONE
    Elapsed....: 00:00:00.0002229
    # per µs...: 0,45
    µs per #...: 2,23

FilterBenchmark.cs

void Main()
{
	var ids = new Guid[100000];
	Run($"Creating test data ({ids.Length} records)", ids.Length, () => {		
		for (var i=0; i < ids.Length; i++) {
			ids[i] = Guid.NewGuid();
		}
	});
	
	var rnd = new Random();
	var subset = new Guid[(int)(ids.Length * 0.01)]; // 1% of total
	var idsIndexes = new HashSet<int>();
	Run($"Creating subset ({subset.Length} records", subset.Length, () => {		
		for (var i=0; i < subset.Length; i++) {
			while (true) {
				var index = rnd.Next(0, ids.Length);
				if (!idsIndexes.Add(index)) continue;
				subset[i] = ids[index];
				break;
			}
		}
	});

	Run($"TEST 1: Filtering with subset as Array", ids.Length, () => ids.Where(id => subset.Contains(id)).ToList());
	var subsetList = subset.ToList();
	Run($"TEST 2: Filtering with subset as List", ids.Length, () => ids.Where(id => subsetList.Contains(id)).ToList());
	var subsetDictionary = subset.ToDictionary(id => id, id => true);
	Run($"TEST 3: Filtering with subset as Dictionary", ids.Length, () => ids.Where(id => subsetDictionary.ContainsKey(id)).ToList());
	var subsetHashSet = new HashSet<Guid>(subset);
	Run($"TEST 4: Filtering with subset as HashSet", ids.Length, () => ids.Where(id => subsetHashSet.Contains(id)).ToList());
}

void Run(string prompt, int records, Action action)
{
	Console.Write($"{prompt}... ");
	var sw = Stopwatch.StartNew();
	action();
	sw.Stop();
	Console.WriteLine("DONE");
	Console.WriteLine($"    Elapsed....: {sw.Elapsed}");
	Console.WriteLine($"    # per µs...: {records / (sw.Elapsed.TotalMilliseconds * 1000):N}");
	Console.WriteLine($"    µs per #...: {(sw.Elapsed.TotalMilliseconds * 1000) / records:N}");
	Console.WriteLine();
}