gistfile1.cs

    public static class TestingClass
	{
		static void Main()
		{
			StringBuilder sb = new StringBuilder("WhereSelect,Select\n");
			Random rnd = new Random();
			const int total = 10000;
			const int onePercent = 100;
			var startList = Enumerable.Range(1, total).Select(i => new MyClass { Value = rnd.Next(0, 10) }).Batch(onePercent).ToList();
			int selectSumTally = 0;
			int whereSelectSumTally = 0;
			int tieTally = 0;
			Console.WriteLine("How much do you want to be the disambiguation percentage?");
			decimal percentToTieFor = decimal.Parse(Console.ReadLine() ?? "1.0");
			Console.WriteLine("File path for csv?");
			string filePath = Console.ReadLine();
			Console.WriteLine("Starting benchmarking.");
			for (int i = 0; i <= 100; i++)
			{
				int i1 = i;
				var testList =
					startList
						.SelectMany((o, inx) => (inx < i1) ? o.Select(mc => ChangeVal(mc, true)) : o.Select(mc => ChangeVal(mc, false)))
						.ToList();
				var selectSum = TimeSpan.FromTicks(0);
				var whereSelectSum = TimeSpan.FromTicks(0);
				for (int n = 0; n < 100; n++)
					selectSum += SelectSumTest(testList);
				GC_CompleteCollect();
				for (int n = 0; n < 100; n++)
					whereSelectSum += WhereSelectSumTest(testList);
				if (whereSelectSum.Ticks.IsWithin(percentToTieFor, selectSum.Ticks))
					tieTally += 1;
				else if (whereSelectSum.Ticks < selectSum.Ticks)
					whereSelectSumTally += 1;
				else
					selectSumTally += 1;
				sb.AppendFormat("{0},{1}\n", whereSelectSum.Ticks, selectSum.Ticks);
				//uncomment to see which iteration it's at
				//Console.WriteLine("Iteration {0} done.", i);
			}
			File.WriteAllText(filePath ?? "", sb.ToString());
			Console.WriteLine("Ties: {0}", tieTally);
			Console.WriteLine("Where + Select: {0}", whereSelectSumTally);
			Console.WriteLine("Select: {0}", selectSumTally);
			Console.ReadKey(true);
		}

		private static TimeSpan SelectSumTest(IEnumerable<MyClass> testEnumerable)
		{
			GC_CompleteCollect();
			Stopwatch sw = Stopwatch.StartNew();
			var result = testEnumerable.Select(mc => mc.IsValid ? mc.Value : 0).Sum();
			sw.Stop();
			GC_CompleteCollect();
			return sw.Elapsed;
		}
		private static TimeSpan WhereSelectSumTest(IEnumerable<MyClass> testEnumerable)
		{
			GC_CompleteCollect();
			Stopwatch sw = Stopwatch.StartNew();
			var result = testEnumerable.Where(mc => mc.IsValid).Select(mc => mc.Value).Sum();
			sw.Stop();
			GC_CompleteCollect();
			return sw.Elapsed;
		}
		private static void GC_CompleteCollect()
		{
			GC.Collect();
			GC.WaitForPendingFinalizers();
			GC.Collect();
		}
		private static MyClass ChangeVal(MyClass mc, bool b)
		{
			mc.IsValid = b;
			return mc;
		}
	}

	public class MyClass
	{
		public int Value { get; set; }
		public bool IsValid { get; set; }
	}

	public static class Extensions
	{
		public static IEnumerable<IEnumerable<T>> Batch<T>(this IEnumerable<T> source, int size)
		{
			Debug.Assert(source != null);
			Debug.Assert(size > 0);
			T[] bucket = null;
			var count = 0;

			foreach (var item in source)
			{
				if (bucket == null)
				{
					bucket = new T[size];
				}

				bucket[count++] = item;

				// The bucket is fully buffered before it's yielded
				if (count != size)
				{
					continue;
				}

				// Select is necessary so bucket contents are streamed too
				yield return bucket.Select(x => x);

				bucket = null;
				count = 0;
			}

			// Return the last bucket with all remaining elements
			if (bucket != null && count > 0)
			{
				yield return bucket.Take(count);
			}
		}

		public static bool IsWithin(this long val, decimal percent, long of)
		{
			var sorted = new[] { val, of }.OrderBy(l => l).ToArray();
			return sorted[1] - (sorted[1] * (percent / 100)) <= sorted[0];
		}
	}