RecyclableList.Contains reworked for performance improvements. 69% vs List.Contains

Recyclable.Collections.Benchmarks/RecyclableCollectionsBenchmarks.List.cs

@@ -111,5 +111,17 @@ namespace Recyclable.Collections.Benchmarks
 			var data = TestObjectsAsList;
 			DoNothing(data.Count);
 		}
+
+		[Benchmark(Baseline = true)]
+		public void List_Contains()
+		{
+			var data = TestObjects;
+			var list = TestObjectsAsList;
+			var dataCount = 100_000;
+			for (var i = 0; i < dataCount; i++)
+			{
+				DoNothing(list.Contains(data[i]));
+			}
+		}
 	}
 }

Recyclable.Collections.Benchmarks/RecyclableCollectionsBenchmarks.RecyclableList.cs

@@ -4,21 +4,21 @@ namespace Recyclable.Collections.Benchmarks
 {
 	public partial class RecyclableCollectionsBenchmarks : BenchmarkBase
 	{
-		[Benchmark]
+		//[Benchmark]
 		public void RecyclableList_Create()
 		{
 			using var list = new RecyclableList<object>();
 			DoNothing(list);
 		}
 
-		[Benchmark]
+		//[Benchmark]
 		public void RecyclableList_Create_WithCapacity()
 		{
 			using var list = new RecyclableList<object>(minBlockSize: 102_400, expectedItemsCount: TestObjectCount);
 			DoNothing(list);
 		}
 
-		[Benchmark]
+		//[Benchmark]
 		public void RecyclableList_Add()
 		{
 			var data = TestObjects;
@@ -30,7 +30,7 @@ namespace Recyclable.Collections.Benchmarks
 			}
 		}
 
-		[Benchmark]
+		//[Benchmark]
 		public void RecyclableList_Add_WithCapacity()
 		{
 			var data = TestObjects;
@@ -77,5 +77,17 @@ namespace Recyclable.Collections.Benchmarks
 			var data = _testRecyclableList;
 			DoNothing(data.LongCount);
 		}
+
+		[Benchmark]
+		public void RecyclableList_Contains()
+		{
+			var data = TestObjects;
+			var list = TestObjectsAsRecyclableList;
+			var dataCount = 100_000;
+			for (var i = 0; i < dataCount; i++)
+			{
+				DoNothing(list.Contains(data[i]));
+			}
+		}
 	}
 }

Recyclable.Collections/RecyclableList.cs

@@ -433,7 +433,7 @@ namespace Recyclable.Collections
 					}
 				}
 
-				_longCount = targetBlockIdx * blockSize + targetItemIdx;
+				_longCount = (targetBlockIdx * blockSize) + targetItemIdx;
 				_lastBlockIndex = targetBlockIdx;
 				_nextItemIndex = targetItemIdx;
 				return;
@@ -510,6 +510,7 @@ namespace Recyclable.Collections
 			_longCount = 0;
 		}
 
+		[MethodImpl(MethodImplOptions.AggressiveInlining)]
 		public bool Contains(T item)
 		{
 			if (_longCount == 0)
@@ -517,101 +518,215 @@ namespace Recyclable.Collections
 				return false;
 			}
 
-			int midPoint = _blockSize / 2;
-			int lastBlockIndex = _lastBlockIndex;
-			int itemIndex0 = 0;
-			int itemIndex1 = midPoint;
+			int blockSize = _blockSize;
+			int itemIndex = 0;
 			int blockIndex = 0;
+			int lastBlockIndex = 0;
 
 			Span<T[]> memoryBlocksSpan = new(_memoryBlocks);
 			Span<T> blockArraySpan = new(memoryBlocksSpan[blockIndex]);
 			if (item != null)
 			{
-				while (blockIndex <= lastBlockIndex)
+				while (blockIndex < lastBlockIndex)
 				{
-					if (item.Equals(blockArraySpan[itemIndex0++]))
+					if (item.Equals(blockArraySpan[itemIndex]))
 					{
 						return true;
 					}
 
-					if (item.Equals(blockArraySpan[itemIndex1++]))
+					if (itemIndex + 1 < blockSize && item.Equals(blockArraySpan[itemIndex + 1]))
+					{
+						return true;
+					}
+					
+					if (itemIndex + 2 < blockSize && item.Equals(blockArraySpan[itemIndex + 2]))
+					{
+						return true;
+					}
+					
+					if (itemIndex + 3 < blockSize && item.Equals(blockArraySpan[itemIndex + 3]))
 					{
 						return true;
 					}
 
-					if (itemIndex0 == midPoint)
+					if (itemIndex + 4 < blockSize && item.Equals(blockArraySpan[itemIndex + 4]))
+					{
+						return true;
+					}
+
+					if (itemIndex + 5 < blockSize && item.Equals(blockArraySpan[itemIndex + 5]))
+					{
+						return true;
+					}
+
+					if (itemIndex + 6 < blockSize && item.Equals(blockArraySpan[itemIndex + 6]))
+					{
+						return true;
+					}
+
+					if (itemIndex + 7 < blockSize && item.Equals(blockArraySpan[itemIndex + 7]))
+					{
+						return true;
+					}
+
+					itemIndex += 8;
+					if (itemIndex >= blockSize)
 					{
 						blockIndex++;
-						if (blockIndex == lastBlockIndex)
-						{
-							int nextItemIndex = _nextItemIndex;
-							if (nextItemIndex == 0)
-							{
-								return false;
-							}
-
-							midPoint = (nextItemIndex / 2) + (nextItemIndex % 2);
-						}
-
 						blockArraySpan = new(memoryBlocksSpan[blockIndex]);
-						itemIndex0 = 0;
-						itemIndex1 = midPoint;
+						itemIndex = 0;
 					}
 				}
+
+				blockArraySpan = new(memoryBlocksSpan[lastBlockIndex]);
+				var nextItemIndex = _nextItemIndex;
+				while (itemIndex < nextItemIndex)
+				{
+					if (item.Equals(blockArraySpan[itemIndex]))
+					{
+						return true;
+					}
+
+					if (itemIndex + 1 < nextItemIndex && item.Equals(blockArraySpan[itemIndex + 1]))
+					{
+						return true;
+					}
+
+					if (itemIndex + 2 < nextItemIndex && item.Equals(blockArraySpan[itemIndex + 2]))
+					{
+						return true;
+					}
+
+					if (itemIndex + 3 < nextItemIndex && item.Equals(blockArraySpan[itemIndex + 3]))
+					{
+						return true;
+					}
+
+					if (itemIndex + 4 < nextItemIndex && item.Equals(blockArraySpan[itemIndex + 4]))
+					{
+						return true;
+					}
+
+					if (itemIndex + 5 < nextItemIndex && item.Equals(blockArraySpan[itemIndex + 5]))
+					{
+						return true;
+					}
+
+					if (itemIndex + 6 < nextItemIndex && item.Equals(blockArraySpan[itemIndex + 6]))
+					{
+						return true;
+					}
+
+					if (itemIndex + 7 < nextItemIndex && item.Equals(blockArraySpan[itemIndex + 7]))
+					{
+						return true;
+					}
+
+					itemIndex += 8;
+				}
 			}
 			else
 			{
 				while (blockIndex < lastBlockIndex)
 				{
-					if (blockArraySpan[itemIndex0++] == null)
+					if (blockArraySpan[itemIndex] == null)
 					{
 						return true;
 					}
 
-					if (blockArraySpan[itemIndex1++] == null)
+					if (itemIndex + 1 < blockSize && blockArraySpan[itemIndex + 1] == null)
 					{
 						return true;
 					}
 
-					if (itemIndex0 == midPoint)
+					if (itemIndex + 2 < blockSize && blockArraySpan[itemIndex + 2] == null)
+					{
+						return true;
+					}
+
+					if (itemIndex + 3 < blockSize && blockArraySpan[itemIndex + 3] == null)
+					{
+						return true;
+					}
+
+					if (itemIndex + 4 < blockSize && blockArraySpan[itemIndex + 4] == null)
+					{
+						return true;
+					}
+
+					if (itemIndex + 5 < blockSize && blockArraySpan[itemIndex + 5] == null)
+					{
+						return true;
+					}
+
+					if (itemIndex + 6 < blockSize && blockArraySpan[itemIndex + 6] == null)
+					{
+						return true;
+					}
+
+					if (itemIndex + 7 < blockSize && blockArraySpan[itemIndex + 7] == null)
+					{
+						return true;
+					}
+
+					itemIndex += 8;
+					if (itemIndex >= blockSize)
 					{
 						blockIndex++;
-						if (blockIndex == lastBlockIndex)
-						{
-							if (_nextItemIndex == 0)
-							{
-								return false;
-							}
-
-							midPoint = ((_nextItemIndex - 1) / 2) + ((_nextItemIndex - 1) % 2);
-						}
-
 						blockArraySpan = new(memoryBlocksSpan[blockIndex]);
-						itemIndex0 = 0;
-						itemIndex1 = 0;
+						itemIndex = 0;
 					}
 				}
+
+				blockArraySpan = new(memoryBlocksSpan[lastBlockIndex]);
+				var nextItemIndex = _nextItemIndex;
+				while (itemIndex < nextItemIndex)
+				{
+					if (blockArraySpan[itemIndex] == null)
+					{
+						return true;
+					}
+
+					if (itemIndex + 1 < nextItemIndex && blockArraySpan[itemIndex + 1] == null)
+					{
+						return true;
+					}
+
+					if (itemIndex + 2 < nextItemIndex && blockArraySpan[itemIndex + 2] == null)
+					{
+						return true;
+					}
+
+					if (itemIndex + 3 < nextItemIndex && blockArraySpan[itemIndex + 3] == null)
+					{
+						return true;
+					}
+
+					if (itemIndex + 4 < nextItemIndex && blockArraySpan[itemIndex + 4] == null)
+					{
+						return true;
+					}
+
+					if (itemIndex + 5 < nextItemIndex && blockArraySpan[itemIndex + 5] == null)
+					{
+						return true;
+					}
+
+					if (itemIndex + 6 < nextItemIndex && blockArraySpan[itemIndex + 6] == null)
+					{
+						return true;
+					}
+
+					if (itemIndex + 7 < nextItemIndex && blockArraySpan[itemIndex + 7] == null)
+					{
+						return true;
+					}
+
+					itemIndex += 8;
+				}
 			}
 
 			return false;
-
-			//for (memoryBlockIndex = 0; memoryBlockIndex < lastBlockIndex; memoryBlockIndex++)
-			//{
-			//	//T? found = Array.Find(memoryBlocksSpan[memoryBlockIndex], x => comparer.Equals(x, item));
-			//	//if (found != null)
-			//	//{
-			//	//	return true;
-			//	//}
-
-			//	blockArraySpan = new(memoryBlocksSpan[memoryBlockIndex]);
-			//	for (itemIndex = 0; itemIndex < mainBlockSize; itemIndex++)
-			//	{
-			//		if (comparer.Equals(blockArraySpan[itemIndex], item))
-			//		{
-			//			return true;
-			//		}
-			//	}
-			//}
 		}
 
 		public void CopyTo(T[] array, int arrayIndex) => _memoryBlocks.CopyTo(0, _blockSize, _longCount, array, arrayIndex);

Recyclable.CollectionsTests/RecyclableListTests.cs

@@ -85,6 +85,53 @@ namespace Recyclable.CollectionsTests
 			_ = list.LongCount.Should().Be(0);
 		}
 
+		[Fact]
+		public void ContainsShouldFindAllItems()
+		{
+			// Prepare
+			var testData = _testData;
+			using var list = NewRecyclableList;
+			_ = testData.Any().Should().BeTrue("we need items on the list that we can look for");
+
+			// Act
+			foreach (var item in testData)
+			{
+				// Validate
+				_ = list.Contains(item).Should().BeTrue();
+			}
+		}
+
+		[Fact]
+		public void ContainsShouldNotFindNonExistingItems()
+		{
+			// Prepare
+			var testData = _testData;
+			using var list = NewRecyclableList;
+			_ = testData.Any().Should().BeTrue("we need items on the list that we can look for");
+
+			// Act
+			foreach (var item in testData)
+			{
+				// Validate
+				_ = list.Contains(-item).Should().BeFalse();
+			}
+
+			// Validate
+			_ = list.Contains(0).Should().BeFalse();
+		}
+
+		[Fact]
+		public void ContainsShouldNotFindAnythingWhenListEmpty()
+		{
+			// Prepare
+			using var list = new RecyclableList<int>();
+
+			// Validate
+			_ = list.Contains(0).Should().BeFalse();
+			_ = list.Contains(1).Should().BeFalse();
+		}
+
+
 		[Fact]
 		public void CopyToShouldCopyAllItems()
 		{