ArrayPool Optimization and cleanup.

Author: electricessence

benchmarking/Program.cs

@@ -6,7 +6,6 @@
 using System;
 using System.Collections.Generic;
 using System.Diagnostics;
-using System.Linq;
 using System.Threading.Tasks;
 
 internal class Program

source/Extensions.Combinations.cs

@@ -23,11 +23,10 @@ static IEnumerable<T[]> CombinationsCore<T>(IReadOnlyList<T> source, int length,
 				if (count == 1) yield break;
 			}
 
-			var pool = ArrayPool<int>.Shared;
-			var indexes = pool.Rent(length);
+			var pool = count > 128 ? ArrayPool<int>.Shared : null;
+			var indexes = pool?.Rent(count) ?? new int[count];
 			try
 			{
-
 				for (var i = 0; i < length; i++) indexes[i] = 0;
 
 				var lastIndex = length - 1;
@@ -68,25 +67,25 @@ bool GetNext()
 			}
 			finally
 			{
-				pool.Return(indexes);
+				pool?.Return(indexes);
 			}
 		}
 
 		static IEnumerable<T[]> CombinationsCore<T>(IReadOnlyList<T> source, int length, bool distinctSet)
 		{
-			var pool = ArrayPool<T>.Shared;
-			var buffer = pool.Rent(length);
+			var pool = length > 128 ? ArrayPool<T>.Shared : null;
+			var buffer = pool?.Rent(length) ?? new T[length];
 			try
 			{
-				foreach (var b in CombinationsCore(source, length,distinctSet, buffer))
+				foreach (var b in CombinationsCore(source, length, distinctSet, buffer))
 					yield return b;
 			}
 			finally
 			{
-				pool.Return(buffer, true);
+				pool?.Return(buffer, true);
 			}
 		}
-	
+
 
 		/// <inheritdoc cref="Combinations{T}(IEnumerable{T}, int)"/>
 		/// <param name="buffer">A buffer that is filled with the values and returned as the yielded value instead of a new array.</param>
@@ -134,7 +133,7 @@ public static IEnumerable<T[]> Combinations<T>(this IEnumerable<T> elements, int
 			if (count == 0) return Enumerable.Empty<T[]>();
 
 			if (uniqueOnly) return source.Subsets(length);
-			return uniqueOnly ? source.Subsets(length) : CombinationsCore(source, length, true).Select(e=>e.AsCopy(length));
+			return uniqueOnly ? source.Subsets(length) : CombinationsCore(source, length, true).Select(e => e.AsCopy(length));
 		}
 
 		/// <inheritdoc cref="Combinations{T}(IEnumerable{T}, int)"/>
@@ -150,8 +149,8 @@ public static IEnumerable<ReadOnlyMemory<T>> CombinationsBuffered<T>(this IEnume
 
 			if (length == 0) yield break;
 
-			var pool = ArrayPool<T>.Shared;
-			var buffer = pool.Rent(length);
+			var pool = length > 128 ? ArrayPool<T>.Shared : null;
+			var buffer = pool?.Rent(length) ?? new T[length];
 			var readBuffer = new ReadOnlyMemory<T>(buffer, 0, length);
 			try
 			{
@@ -160,7 +159,7 @@ public static IEnumerable<ReadOnlyMemory<T>> CombinationsBuffered<T>(this IEnume
 			}
 			finally
 			{
-				pool.Return(buffer, true);
+				pool?.Return(buffer, true);
 			}
 		}
 
@@ -178,8 +177,8 @@ public static IEnumerable<ReadOnlyMemory<T>> CombinationsDistinctBuffered<T>(thi
 
 			if (length == 0) yield break;
 
-			var pool = ArrayPool<T>.Shared;
-			var buffer = pool.Rent(length);
+			var pool = length > 128 ? ArrayPool<T>.Shared : null;
+			var buffer = pool?.Rent(length) ?? new T[length];
 			var readBuffer = new ReadOnlyMemory<T>(buffer, 0, length);
 			try
 			{
@@ -188,7 +187,7 @@ public static IEnumerable<ReadOnlyMemory<T>> CombinationsDistinctBuffered<T>(thi
 			}
 			finally
 			{
-				pool.Return(buffer, true);
+				pool?.Return(buffer, true);
 			}
 		}
 

source/Extensions.Permutations.cs

@@ -77,8 +77,8 @@ public static IEnumerable<ReadOnlyMemory<T>> PermutationsBuffered<T>(this IReadO
 			var count = elements.Count;
 			if (count == 0) yield break;
 
-			var pool = ArrayPool<T>.Shared;
-			var buffer = pool.Rent(count);
+			var pool = count > 128 ? ArrayPool<T>.Shared : null;
+			var buffer = pool?.Rent(count) ?? new T[count];
 			var readBuffer = new ReadOnlyMemory<T>(buffer, 0, count);
 			try
 			{
@@ -87,7 +87,7 @@ public static IEnumerable<ReadOnlyMemory<T>> PermutationsBuffered<T>(this IReadO
 			}
 			finally
 			{
-				pool.Return(buffer, true);
+				pool?.Return(buffer, true);
 			}
 		}
 

source/Extensions.Stream.cs

@@ -16,9 +16,8 @@ public static void CopyTo(this Stream source, Stream target, int bufferSize = 40
 			if (target is null)
 				throw new ArgumentNullException(nameof(target));
 
-			var pool = ArrayPool<byte>.Shared;
-			var bytes = pool.Rent(bufferSize);
-
+			var pool = bufferSize > 128 ? ArrayPool<byte>.Shared : null;
+			var bytes = pool?.Rent(bufferSize) ?? new byte[bufferSize];
 			try
 			{
 				int cnt;
@@ -27,7 +26,7 @@ public static void CopyTo(this Stream source, Stream target, int bufferSize = 40
 			}
 			finally
 			{
-				pool.Return(bytes, clearBufferAfter);
+				pool?.Return(bytes, clearBufferAfter);
 			}
 		}
 	}

source/Extensions.Subsets.cs

@@ -34,7 +34,7 @@ public static IEnumerable<T[]> Subsets<T>(this IReadOnlyList<T> source, int coun
 			}
 
 			var diff = source.Count - count;
-			var pool = count>128 ? ArrayPool<int>.Shared : null;
+			var pool = count > 128 ? ArrayPool<int>.Shared : null;
 			var indices = pool?.Rent(count) ?? new int[count];
 			try
 			{

source/LazyList.cs

@@ -3,7 +3,6 @@
  * Partly based on: http://www.fallingcanbedeadly.com/posts/crazy-extention-methods-tolazylist/
  */
 
-using Open.Disposable;
 using Open.Threading;
 using System;
 using System.Collections.Generic;
@@ -44,7 +43,7 @@ protected override void OnDispose()
 		/// <inheritdoc/>
 		public override int IndexOf(T item)
 		{
-			const string MESSAGE = MARKED_ENDLESS+" Use an enumerator, then Take(x).IndexOf().";
+			const string MESSAGE = MARKED_ENDLESS + " Use an enumerator, then Take(x).IndexOf().";
 			if (IsEndless) throw new InvalidOperationException(MESSAGE);
 
 			return base.IndexOf(item);

source/Subsets.cs

@@ -68,8 +68,8 @@ public static IEnumerable<int[]> Indexes(int sourceLength, int subsetLength, int
 		/// <remarks>Values are yielded as read only memory buffer that should not be retained as its array is returned to pool afterwards.</remarks>
 		public static IEnumerable<ReadOnlyMemory<int>> IndexesBuffered(int sourceLength, int subsetLength)
 		{
-			var pool = ArrayPool<int>.Shared;
-			var buffer = pool.Rent(subsetLength);
+			var pool = subsetLength > 128 ? ArrayPool<int>.Shared : null;
+			var buffer = pool?.Rent(subsetLength) ?? new int[subsetLength];
 			var readBuffer = new ReadOnlyMemory<int>(buffer, 0, subsetLength);
 			try
 			{
@@ -78,7 +78,7 @@ public static IEnumerable<ReadOnlyMemory<int>> IndexesBuffered(int sourceLength,
 			}
 			finally
 			{
-				pool.Return(buffer, true);
+				pool?.Return(buffer, true);
 			}
 		}
 

source/Synchronized/ReadWriteSynchronizedCollectionWrapper.cs

@@ -84,7 +84,7 @@ public override Span<T> CopyTo(Span<T> span)
 			using var read = Sync.ReadLock();
 			return InternalSource.CopyToSpan(span);
 		}
-			
+
 		#endregion
 
 		#region Dispose

testing/Open.Collections.Tests/LazyListTests.cs

@@ -1,8 +1,5 @@
 using System;
-using System.Collections.Generic;
 using System.Linq;
-using System.Text;
-using System.Threading.Tasks;
 using Xunit;
 
 namespace Open.Collections.Tests

testing/Open.Collections.Tests/SubsetTests.cs

@@ -129,7 +129,7 @@ public void TestSubset4_3()
 		[InlineData(16, 4)]
 		public void LargerProgressiveCheck(int size, int count)
 		{
-			
+
 			var FullSet = Enumerable.Range(1, size).ToImmutableArray();
 			var buffer = new int[count];
 			var s1 = FullSet.Subsets(count, buffer).ToImmutableArray();