Collection resize benchmark

collection-resize-benchmark.cs

#LINQPad optimize+
void Main()
{
	var summary = BenchmarkRunner.Run<HashSetPerformance>();
}

[MemoryDiagnoser]
public class HashSetPerformance
{
	[Params(100, 1000, 10000, 100_000)]
	public int CollectionSize;
	
	[Benchmark]
	public void SizeDefined()
	{
		int itemsCount = CollectionSize;

		HashSet<int> set = new HashSet<int>(itemsCount);
		foreach (var i in Enumerable.Range(0, itemsCount))
		{
			set.Add(i);
		}
	}

	[Benchmark]
	public void SizeDefinedWithEnsureCapacity()
	{
		int itemsCount = CollectionSize;

		HashSet<int> set = new HashSet<int>();
		set.EnsureCapacity(itemsCount);
		foreach (var i in Enumerable.Range(0, itemsCount))
		{
			set.Add(i);
		}
	}


	[Benchmark]
	public void SizeNotDefined()
	{
		int itemsCount = CollectionSize;

		HashSet<int> set = new HashSet<int>();
		foreach (var i in Enumerable.Range(0, itemsCount))
		{
			set.Add(i);
		}
	}
}