Implement LFU sketch using arm64 intrinsics (redux)

BitFaster.Caching.Benchmarks/BitFaster.Caching.Benchmarks.csproj

@@ -3,12 +3,14 @@
   <PropertyGroup>
     <OutputType>Exe</OutputType>
     <LangVersion>latest</LangVersion>
-    <TargetFrameworks>net48;net6.0;net8.0</TargetFrameworks>
+    <TargetFrameworks>net6.0;net8.0</TargetFrameworks>
     <AllowUnsafeBlocks>True</AllowUnsafeBlocks>
     <!-- https://stackoverflow.com/a/59916801/131345 -->
     <IsWindows Condition="'$([System.Runtime.InteropServices.RuntimeInformation]::IsOSPlatform($([System.Runtime.InteropServices.OSPlatform]::Windows)))' == 'true'">true</IsWindows> 
     <IsLinux Condition="'$([System.Runtime.InteropServices.RuntimeInformation]::IsOSPlatform($([System.Runtime.InteropServices.OSPlatform]::Linux)))' == 'true'">true</IsLinux>
     <IsMacOS Condition="'$([System.Runtime.InteropServices.RuntimeInformation]::IsOSPlatform($([System.Runtime.InteropServices.OSPlatform]::OSX)))' == 'true'">true</IsMacOS>
+    <IsArm64 Condition="$([System.Runtime.InteropServices.RuntimeInformation]::OSArchitecture) == Arm64">true</IsArm64>
+    <IsX64 Condition="$([System.Runtime.InteropServices.RuntimeInformation]::OSArchitecture) == X64">true</IsX64>
   </PropertyGroup>
 
   <PropertyGroup Condition="'$(Configuration)|$(Platform)'=='Release|AnyCPU'">
@@ -41,5 +43,11 @@
     <PropertyGroup Condition="'$(IsMacOS)'=='true'">
         <DefineConstants>MacOS</DefineConstants>
     </PropertyGroup>
+    <PropertyGroup Condition="'$(IsArm64)'=='true'">
+        <DefineConstants>Arm64</DefineConstants>
+    </PropertyGroup>
+    <PropertyGroup Condition="'$(IsX64)'=='true'">
+        <DefineConstants>X64</DefineConstants>
+    </PropertyGroup>
 
-</Project>
+</Project>

BitFaster.Caching.Benchmarks/Lfu/CmSketchNoPin.cs

@@ -1,9 +1,12 @@
 using System;
 using System.Collections.Generic;
 using System.Diagnostics.CodeAnalysis;
+using System.Runtime.CompilerServices;
+
 
 #if NET6_0_OR_GREATER
 using System.Runtime.Intrinsics;
+using System.Runtime.Intrinsics.Arm;
 using System.Runtime.Intrinsics.X86;
 #endif
 
@@ -61,6 +64,12 @@ public int EstimateFrequency(T value)
             {
                 return EstimateFrequencyAvx(value);
             }
+#if NET6_0_OR_GREATER
+            else if (isa.IsArm64Supported)
+            {
+                return EstimateFrequencyArm(value);
+            }
+#endif
             else
             {
                 return EstimateFrequencyStd(value);
@@ -84,6 +93,12 @@ public void Increment(T value)
             {
                 IncrementAvx(value);
             }
+#if NET6_0_OR_GREATER
+            else if (isa.IsArm64Supported)
+            {
+                IncrementArm(value);
+            }
+#endif
             else
             {
                 IncrementStd(value);
@@ -314,5 +329,94 @@ private unsafe void IncrementAvx(T value)
             }
         }
 #endif
+
+#if NET6_0_OR_GREATER
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        private unsafe void IncrementArm(T value)
+        {
+            int blockHash = Spread(comparer.GetHashCode(value));
+            int counterHash = Rehash(blockHash);
+            int block = (blockHash & blockMask) << 3;
+
+            Vector128<int> h = AdvSimd.ShiftArithmetic(Vector128.Create(counterHash), Vector128.Create(0, -8, -16, -24));
+            Vector128<int> index = AdvSimd.And(AdvSimd.ShiftRightLogical(h, 1), Vector128.Create(0xf));
+            Vector128<int> blockOffset = AdvSimd.Add(AdvSimd.Add(Vector128.Create(block), AdvSimd.And(h, Vector128.Create(1))), Vector128.Create(0, 2, 4, 6));
+
+            fixed (long* tablePtr = table)
+            {
+                int t0 = AdvSimd.Extract(blockOffset, 0);
+                int t1 = AdvSimd.Extract(blockOffset, 1);
+                int t2 = AdvSimd.Extract(blockOffset, 2);
+                int t3 = AdvSimd.Extract(blockOffset, 3);
+
+                Vector128<long> tableVectorA = Vector128.Create(AdvSimd.LoadVector64(tablePtr + t0), AdvSimd.LoadVector64(tablePtr + t1));
+                Vector128<long> tableVectorB = Vector128.Create(AdvSimd.LoadVector64(tablePtr + t2), AdvSimd.LoadVector64(tablePtr + t3));
+
+                index = AdvSimd.ShiftLeftLogicalSaturate(index, 2);
+
+                Vector128<int> longOffA = AdvSimd.Arm64.InsertSelectedScalar(AdvSimd.Arm64.InsertSelectedScalar(Vector128<int>.Zero, 0, index, 0), 2, index, 1);
+                Vector128<int> longOffB = AdvSimd.Arm64.InsertSelectedScalar(AdvSimd.Arm64.InsertSelectedScalar(Vector128<int>.Zero, 0, index, 2), 2, index, 3);
+
+                Vector128<long> fifteen = Vector128.Create(0xfL);
+                Vector128<long> maskA = AdvSimd.ShiftArithmetic(fifteen, longOffA.AsInt64());
+                Vector128<long> maskB = AdvSimd.ShiftArithmetic(fifteen, longOffB.AsInt64());
+
+                Vector128<long> maskedA = AdvSimd.Not(AdvSimd.Arm64.CompareEqual(AdvSimd.And(tableVectorA, maskA), maskA));
+                Vector128<long> maskedB = AdvSimd.Not(AdvSimd.Arm64.CompareEqual(AdvSimd.And(tableVectorB, maskB), maskB));
+
+                var one = Vector128.Create(1L);
+                Vector128<long> incA = AdvSimd.And(maskedA, AdvSimd.ShiftArithmetic(one, longOffA.AsInt64()));
+                Vector128<long> incB = AdvSimd.And(maskedB, AdvSimd.ShiftArithmetic(one, longOffB.AsInt64()));
+
+                tablePtr[t0] += AdvSimd.Extract(incA, 0);
+                tablePtr[t1] += AdvSimd.Extract(incA, 1);
+                tablePtr[t2] += AdvSimd.Extract(incB, 0);
+                tablePtr[t3] += AdvSimd.Extract(incB, 1);
+
+                var max = AdvSimd.Arm64.MaxAcross(AdvSimd.Arm64.InsertSelectedScalar(AdvSimd.Arm64.MaxAcross(incA.AsInt32()), 1, AdvSimd.Arm64.MaxAcross(incB.AsInt32()), 0).AsInt16());
+
+                if (max.ToScalar() != 0 && (++size == sampleSize))
+                {
+                    Reset();
+                }
+            }
+        }
+
+        [MethodImpl(MethodImplOptions.AggressiveInlining)]
+        private unsafe int EstimateFrequencyArm(T value)
+        {
+            int blockHash = Spread(comparer.GetHashCode(value));
+            int counterHash = Rehash(blockHash);
+            int block = (blockHash & blockMask) << 3;
+
+            Vector128<int> h = AdvSimd.ShiftArithmetic(Vector128.Create(counterHash), Vector128.Create(0, -8, -16, -24));
+            Vector128<int> index = AdvSimd.And(AdvSimd.ShiftRightLogical(h, 1), Vector128.Create(0xf));
+            Vector128<int> blockOffset = AdvSimd.Add(AdvSimd.Add(Vector128.Create(block), AdvSimd.And(h, Vector128.Create(1))), Vector128.Create(0, 2, 4, 6));
+
+            fixed (long* tablePtr = table)
+            {
+                Vector128<long> tableVectorA = Vector128.Create(AdvSimd.LoadVector64(tablePtr + AdvSimd.Extract(blockOffset, 0)), AdvSimd.LoadVector64(tablePtr + AdvSimd.Extract(blockOffset, 1)));
+                Vector128<long> tableVectorB = Vector128.Create(AdvSimd.LoadVector64(tablePtr + AdvSimd.Extract(blockOffset, 2)), AdvSimd.LoadVector64(tablePtr + AdvSimd.Extract(blockOffset, 3)));
+
+                index = AdvSimd.ShiftLeftLogicalSaturate(index, 2);
+
+                Vector128<int> indexA = AdvSimd.Negate(AdvSimd.Arm64.InsertSelectedScalar(AdvSimd.Arm64.InsertSelectedScalar(Vector128<int>.Zero, 0, index, 0), 2, index, 1));
+                Vector128<int> indexB = AdvSimd.Negate(AdvSimd.Arm64.InsertSelectedScalar(AdvSimd.Arm64.InsertSelectedScalar(Vector128<int>.Zero, 0, index, 2), 2, index, 3));
+
+                var fifteen = Vector128.Create(0xfL);
+                Vector128<long> a = AdvSimd.And(AdvSimd.ShiftArithmetic(tableVectorA, indexA.AsInt64()), fifteen);
+                Vector128<long> b = AdvSimd.And(AdvSimd.ShiftArithmetic(tableVectorB, indexB.AsInt64()), fifteen);
+
+                // Before: < 0, 1, 2, 3, 4, 5, 6, 7, 8, 9, A, B, C, D, E, F >
+                // After:  < 0, 1, 2, 3, 8, 9, A, B, 4, 5, 6, 7, C, D, E, F >
+                var min = AdvSimd.Arm64.VectorTableLookup(a.AsByte(), Vector128.Create(0x0B0A090803020100, 0xFFFFFFFFFFFFFFFF).AsByte());
+                min = AdvSimd.Arm64.VectorTableLookupExtension(min, b.AsByte(), Vector128.Create(0xFFFFFFFFFFFFFFFF, 0x0B0A090803020100).AsByte());
+
+                var min32 = AdvSimd.Arm64.MinAcross(min.AsInt32());
+
+                return min32.ToScalar();
+            }
+        }
+#endif
     }
 }

BitFaster.Caching.Benchmarks/Lfu/SketchFrequency.cs

@@ -51,7 +51,7 @@ public int FrequencyFlat()
 
             return count;
         }
-
+#if X64
         [Benchmark(OperationsPerInvoke = iterations)]
         public int FrequencyFlatAvx()
         {
@@ -61,7 +61,7 @@ public int FrequencyFlatAvx()
 
             return count;
         }
-
+#endif
         [Benchmark(OperationsPerInvoke = iterations)]
         public int FrequencyBlock()
         {
@@ -73,7 +73,11 @@ public int FrequencyBlock()
         }
 
         [Benchmark(OperationsPerInvoke = iterations)]
+#if Arm64
+        public int FrequencyBlockNeonNotPinned()
+#else
         public int FrequencyBlockAvxNotPinned()
+#endif
         {
             int count = 0;
             for (int i = 0; i < iterations; i++)
@@ -83,7 +87,12 @@ public int FrequencyBlockAvxNotPinned()
         }
 
         [Benchmark(OperationsPerInvoke = iterations)]
+
+#if Arm64
+        public int FrequencyBlockNeonPinned()
+#else
         public int FrequencyBlockAvxPinned()
+#endif
         {
             int count = 0;
             for (int i = 0; i < iterations; i++)

BitFaster.Caching.Benchmarks/Lfu/SketchIncrement.cs

@@ -27,6 +27,7 @@ public class SketchIncrement
         private CmSketchNoPin<int, DetectIsa> blockAvxNoPin;
         private CmSketchCore<int, DetectIsa> blockAvx;
 
+
         [Params(32_768, 524_288, 8_388_608, 134_217_728)]
         public int Size { get; set; }
 
@@ -49,7 +50,7 @@ public void IncFlat()
                 flatStd.Increment(i);
             }
         }
-
+#if X64
         [Benchmark(OperationsPerInvoke = iterations)]
         public void IncFlatAvx()
         {
@@ -58,7 +59,7 @@ public void IncFlatAvx()
                 flatAvx.Increment(i);
             }
         }
-
+#endif
         [Benchmark(OperationsPerInvoke = iterations)]
         public void IncBlock()
         {
@@ -69,7 +70,11 @@ public void IncBlock()
         }
 
         [Benchmark(OperationsPerInvoke = iterations)]
+#if Arm64
+        public void IncBlockNeonNotPinned()
+#else
         public void IncBlockAvxNotPinned()
+#endif
         {
             for (int i = 0; i < iterations; i++)
             {
@@ -78,7 +83,11 @@ public void IncBlockAvxNotPinned()
         }
 
         [Benchmark(OperationsPerInvoke = iterations)]
+#if Arm64
+        public void IncBlockNeonPinned()
+#else
         public void IncBlockAvxPinned()
+#endif
         {
             for (int i = 0; i < iterations; i++)
             {

BitFaster.Caching.UnitTests/Intrinsics.cs

@@ -1,6 +1,10 @@
 #if NETCOREAPP3_1_OR_GREATER
 using System.Runtime.Intrinsics.X86;
 #endif
+#if NET6_0_OR_GREATER
+using System.Runtime.Intrinsics.Arm;
+#endif
+
 using Xunit;
 
 namespace BitFaster.Caching.UnitTests
@@ -10,8 +14,14 @@ public static class Intrinsics
         public static void SkipAvxIfNotSupported<I>()
         {
 #if NETCOREAPP3_1_OR_GREATER
+    #if NET6_0_OR_GREATER
+            // when we are trying to test Avx2/Arm64, skip the test if it's not supported
+            Skip.If(typeof(I) == typeof(DetectIsa) && !(Avx2.IsSupported || AdvSimd.Arm64.IsSupported));
+    #else
             // when we are trying to test Avx2, skip the test if it's not supported
             Skip.If(typeof(I) == typeof(DetectIsa) && !Avx2.IsSupported);
+    #endif
+
 #else
             Skip.If(true);
 #endif

BitFaster.Caching.UnitTests/Lfu/CmSketchTests.cs

@@ -6,12 +6,12 @@
 
 namespace BitFaster.Caching.UnitTests.Lfu
 {
-    // Test with AVX2 if it is supported
-    public class CMSketchAvx2Tests : CmSketchTestBase<DetectIsa>
+    // Test with AVX2/ARM64 if it is supported
+    public class CMSketchIntrinsicsTests : CmSketchTestBase<DetectIsa>
     {
     }
 
-    // Test with AVX2 disabled
+    // Test with AVX2/ARM64 disabled
     public class CmSketchTests : CmSketchTestBase<DisableHardwareIntrinsics>
     {
     }
@@ -29,14 +29,23 @@ public CmSketchTestBase()
         public void Repro()
         {
             sketch = new CmSketchCore<int, I>(1_048_576, EqualityComparer<int>.Default);
+            var baseline = new CmSketchCore<int, DisableHardwareIntrinsics>(1_048_576, EqualityComparer<int>.Default);
 
             for (int i = 0; i < 1_048_576; i++)
             {
                 if (i % 3 == 0)
                 {
                     sketch.Increment(i);
+                    baseline.Increment(i);
                 }
             }
+
+            baseline.Size.Should().Be(sketch.Size);
+
+            for (int i = 0; i < 1_048_576; i++)
+            {
+                sketch.EstimateFrequency(i).Should().Be(baseline.EstimateFrequency(i));
+            }
         }
 
 

BitFaster.Caching/Intrinsics.cs

@@ -2,6 +2,10 @@
 using System.Runtime.Intrinsics.X86;
 #endif
 
+#if NET6_0
+using System.Runtime.Intrinsics.Arm;
+#endif
+
 namespace BitFaster.Caching
 {
     /// <summary>
@@ -12,7 +16,14 @@ public interface IsaProbe
         /// <summary>
         /// Gets a value indicating whether AVX2 is supported.
         /// </summary>
-        bool IsAvx2Supported { get; }
+        bool IsAvx2Supported { get; }
+
+#if NET6_0_OR_GREATER
+        /// <summary>
+        /// Gets a value indicating whether Arm64 is supported.
+        /// </summary>
+        bool IsArm64Supported { get => false; }
+#endif
     }
 
     /// <summary>
@@ -25,7 +36,15 @@ public interface IsaProbe
         public bool IsAvx2Supported => false;
 #else
         /// <inheritdoc/>
-        public bool IsAvx2Supported => Avx2.IsSupported;
+        public bool IsAvx2Supported => Avx2.IsSupported;
+#endif
+
+#if NET6_0_OR_GREATER
+        /// <inheritdoc/>
+        public bool IsArm64Supported => AdvSimd.Arm64.IsSupported;
+#else
+        /// <inheritdoc/>
+        public bool IsArm64Supported => false;
 #endif
     }
 
@@ -35,6 +54,9 @@ public interface IsaProbe
     public readonly struct DisableHardwareIntrinsics : IsaProbe
     {
         /// <inheritdoc/>
-        public bool IsAvx2Supported => false;
+        public bool IsAvx2Supported => false;
+
+        /// <inheritdoc/>
+        public bool IsArm64Supported => false;
     }
 }