[Union] use visitor to improve performance.

Author: reegeek

Documents/BenchmarksResults/Union.md

@@ -16,8 +16,8 @@ Intel Core i7-7700 CPU 3.60GHz (Kaby Lake), 1 CPU, 8 logical and 4 physical core
 ```
 |                            Method |     Mean |   Error |  StdDev | Ratio |   Gen 0 |   Gen 1 |   Gen 2 | Allocated |
 |---------------------------------- |---------:|--------:|--------:|------:|--------:|--------:|--------:|----------:|
-|                              Linq | 424.0 μs | 8.27 μs | 7.74 μs |  1.00 | 90.8203 | 90.8203 | 90.8203 |  524824 B |
-|                        StructLinq | 184.9 μs | 2.72 μs | 2.42 μs |  0.44 |       - |       - |       - |      64 B |
-|               StructLinqZeroAlloc | 184.4 μs | 1.89 μs | 1.58 μs |  0.43 |       - |       - |       - |         - |
-|    StructLinqZeroAllocAndComparer | 149.1 μs | 0.82 μs | 0.69 μs |  0.35 |       - |       - |       - |         - |
-| StructLinqZeroAllocAndComparerSum | 132.7 μs | 0.41 μs | 0.37 μs |  0.31 |       - |       - |       - |         - |
+|                              Linq | 430.9 μs | 3.74 μs | 3.12 μs |  1.00 | 90.8203 | 90.8203 | 90.8203 |  524824 B |
+|                        StructLinq | 182.4 μs | 3.57 μs | 3.34 μs |  0.42 |       - |       - |       - |      64 B |
+|               StructLinqZeroAlloc | 187.4 μs | 3.61 μs | 3.71 μs |  0.43 |       - |       - |       - |         - |
+|    StructLinqZeroAllocAndComparer | 152.3 μs | 2.96 μs | 3.40 μs |  0.36 |       - |       - |       - |         - |
+| StructLinqZeroAllocAndComparerSum | 109.8 μs | 2.19 μs | 3.48 μs |  0.25 |       - |       - |       - |         - |

src/StructLinq.Tests/UnionTests.cs

@@ -30,5 +30,17 @@ public void SameAsSystem()
             var value = array1.ToStructEnumerable().Union(array2.ToStructEnumerable()).ToArray();
             Assert.Equal(expected, value);
         }
+
+        [Fact]
+        public void SameAsSystemEnumerable()
+        {
+            var array1 = new int[] { 1, 1, 2, 3, 4, 4, 5 };
+            var array2 = new int[] { 4, 5, 6, 6, 7, 8, 9 };
+
+            var expected = array1.Union(array2);
+            var value = array1.ToStructEnumerable().Union(array2.ToStructEnumerable()).ToEnumerable();
+            Assert.Equal(expected, value);
+        }
+
     }
 }

src/StructLinq/Distinct/DistinctEnumerable.cs

@@ -1,6 +1,7 @@
 using System.Buffers;
 using System.Collections.Generic;
 using System.Runtime.CompilerServices;
+using StructLinq.Utils;
 using StructLinq.Utils.Collections;
 
 namespace StructLinq.Distinct
@@ -38,36 +39,11 @@ public DistinctEnumerator<T, TEnumerator, TComparer> GetEnumerator()
         public VisitStatus Visit<TVisitor>(ref TVisitor visitor)
             where TVisitor : IVisitor<T>
         {
-            var distinctVisitor = new DistinctVisitor<TVisitor>(capacity, bucketPool, slotPool, comparer, ref visitor);
+            var distinctVisitor = new DistinctVisitor<T, TComparer, TVisitor>(capacity, bucketPool, slotPool, comparer, ref visitor);
             var visitStatus = enumerable.Visit(ref distinctVisitor);
-            visitor = distinctVisitor.visitor;
+            visitor = distinctVisitor.Visitor;
             distinctVisitor.Dispose();
             return visitStatus;
         }
-
-        private struct DistinctVisitor<TVisitor> : IVisitor<T>
-            where TVisitor : IVisitor<T>
-        {
-            public TVisitor visitor;
-            private PooledSet<T, TComparer> set;
-
-            public DistinctVisitor(int capacity, ArrayPool<int> bucketPool, ArrayPool<Slot<T>> slotPool, TComparer comparer, ref TVisitor visitor)
-            {
-                this.visitor = visitor;
-                set = new PooledSet<T, TComparer>(capacity, bucketPool, slotPool, comparer);
-            }
-
-            [MethodImpl(MethodImplOptions.AggressiveInlining)]
-            public bool Visit(T input)
-            {
-                return !set.AddIfNotPresent(input) || visitor.Visit(input);
-            }
-
-            [MethodImpl(MethodImplOptions.AggressiveInlining)]
-            public void Dispose()
-            {
-                set.Dispose();
-            }
-        }
     }
 }

src/StructLinq/Union/UnionEnumerable.cs

@@ -1,6 +1,7 @@
 using System.Buffers;
 using System.Collections.Generic;
 using System.Runtime.CompilerServices;
+using StructLinq.Utils;
 using StructLinq.Utils.Collections;
 
 namespace StructLinq.Union
@@ -44,13 +45,15 @@ public UnionEnumerator<T, TEnumerator1, TEnumerator2, TComparer> GetEnumerator()
         public VisitStatus Visit<TVisitor>(ref TVisitor visitor)
             where TVisitor : IVisitor<T>
         {
-            foreach (var input in this)
+            var distinctVisitor = new DistinctVisitor<T, TComparer, TVisitor>(capacity, bucketPool, slotPool, comparer, ref visitor);
+            var visitStatus = enumerable1.Visit(ref distinctVisitor);
+            if (visitStatus != VisitStatus.VisitorFinished)
             {
-                if (!visitor.Visit(input))
-                    return VisitStatus.VisitorFinished;
+                visitStatus = enumerable2.Visit(ref distinctVisitor);
             }
-
-            return VisitStatus.EnumeratorFinished;
+            visitor = distinctVisitor.Visitor;
+            distinctVisitor.Dispose();
+            return visitStatus;
         }
     }
 }

src/StructLinq/Utils/DistinctVisitor.cs

@@ -0,0 +1,33 @@
+using System.Buffers;
+using System.Collections.Generic;
+using System.Runtime.CompilerServices;
+using StructLinq.Utils.Collections;
+
+namespace StructLinq.Utils
+{
+    internal struct DistinctVisitor<T, TComparer, TVisitor> : IVisitor<T>
+        where TComparer : IEqualityComparer<T>
+        where TVisitor : IVisitor<T>
+    {
+        public TVisitor Visitor;
+        private PooledSet<T, TComparer> set;
+
+        public DistinctVisitor(int capacity, ArrayPool<int> bucketPool, ArrayPool<Slot<T>> slotPool, TComparer comparer, ref TVisitor visitor)
+        {
+            this.Visitor = visitor;
+            set = new PooledSet<T, TComparer>(capacity, bucketPool, slotPool, comparer);
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public bool Visit(T input)
+        {
+            return !set.AddIfNotPresent(input) || Visitor.Visit(input);
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        public void Dispose()
+        {
+            set.Dispose();
+        }
+    }
+}