IterateArray benchmark

tests/ImageSharp.Benchmarks/General/IterateArray.cs

@@ -0,0 +1,70 @@
+namespace ImageSharp.Benchmarks.General
+{
+    using System.Numerics;
+    using System.Runtime.CompilerServices;
+
+    using BenchmarkDotNet.Attributes;
+
+    public class IterateArray
+    {
+        // Usual pinned stuff
+        private PinnedBuffer<Vector4> buffer;
+
+        // An array that's not pinned by intent!
+        private Vector4[] array;
+        
+        [Params(64, 1024)]
+        public int Length { get; set; }
+
+        [Setup]
+        public void Setup()
+        {
+            this.buffer = new PinnedBuffer<Vector4>(this.Length);
+            this.array = new Vector4[this.Length];
+        }
+
+        [Benchmark(Baseline = true)]
+        public Vector4 IterateIndexed()
+        {
+            Vector4 sum = new Vector4();
+            Vector4[] a = this.array;
+
+            for (int i = 0; i < a.Length; i++)
+            {
+                sum += a[i];
+            }
+            return sum;
+        }
+
+        [Benchmark]
+        public unsafe Vector4 IterateUsingPointers()
+        {
+            Vector4 sum = new Vector4();
+
+            Vector4* ptr = (Vector4*) this.buffer.Pointer;
+            Vector4* end = ptr + this.Length;
+
+            for (; ptr < end; ptr++)
+            {
+                sum += *ptr;
+            }
+
+            return sum;
+        }
+
+        [Benchmark]
+        public Vector4 IterateUsingReferences()
+        {
+            Vector4 sum = new Vector4();
+
+            ref Vector4 start = ref this.array[0];
+
+            for (int i = 0; i < this.Length; i++)
+            {
+                sum += Unsafe.Add(ref start, i);
+            }
+
+            return sum;
+        }
+    }
+}