Implement LFU sketch using arm64 intrinsics

BitFaster.Caching.Benchmarks/Lfu/SketchFrequency.cs

@@ -8,6 +8,7 @@
 namespace BitFaster.Caching.Benchmarks.Lfu
 {
     [SimpleJob(RuntimeMoniker.Net60)]
+    [SimpleJob(RuntimeMoniker.Net80)]
     [MemoryDiagnoser(displayGenColumns: false)]
     [HideColumns("Job", "Median", "RatioSD", "Alloc Ratio")]
     [ColumnChart(Title ="Sketch Frequency ({JOB})")]
@@ -22,7 +23,7 @@ public class SketchFrequency
         private CmSketchCore<int, DisableHardwareIntrinsics> blockStd;
         private CmSketchCore<int, DetectIsa> blockAvx;
 
-        [Params(32_768, 524_288, 8_388_608, 134_217_728)]
+        [Params(1024, 32_768, 524_288, 8_388_608, 134_217_728)]
         public int Size { get; set; }
 
         [GlobalSetup]
@@ -45,7 +46,7 @@ public int FrequencyFlat()
             return count;
         }
 
-        [Benchmark(OperationsPerInvoke = iterations)]
+       // [Benchmark(OperationsPerInvoke = iterations)]
         public int FrequencyFlatAvx()
         {
             int count = 0;

BitFaster.Caching.Benchmarks/Lfu/SketchIncrement.cs

@@ -1,14 +1,17 @@
 
 using System.Collections.Generic;
+using Benchly;
 using BenchmarkDotNet.Attributes;
 using BenchmarkDotNet.Jobs;
 using BitFaster.Caching.Lfu;
 
 namespace BitFaster.Caching.Benchmarks.Lfu
 {
     [SimpleJob(RuntimeMoniker.Net60)]
+    [SimpleJob(RuntimeMoniker.Net80)]
     [MemoryDiagnoser(displayGenColumns: false)]
     [HideColumns("Job", "Median", "RatioSD", "Alloc Ratio")]
+    [ColumnChart(Title = "Sketch Increment ({JOB})")]
     public class SketchIncrement
     {
         const int iterations = 1_048_576;
@@ -19,7 +22,7 @@ public class SketchIncrement
         private CmSketchCore<int, DisableHardwareIntrinsics> blockStd;
         private CmSketchCore<int, DetectIsa> blockAvx;
 
-        [Params(32_768, 524_288, 8_388_608, 134_217_728)]
+        [Params(1024, 32_768, 524_288, 8_388_608, 134_217_728)]
         public int Size { get; set; }
 
         [GlobalSetup]
@@ -41,7 +44,7 @@ public void IncFlat()
             }
         }
 
-        [Benchmark(OperationsPerInvoke = iterations)]
+        //[Benchmark(OperationsPerInvoke = iterations)]
         public void IncFlatAvx()
         {
             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;
     }
 }

BitFaster.Caching/Lfu/CmSketchCore.cs

@@ -1,13 +1,18 @@
 using System;
 using System.Collections.Generic;
 using System.Diagnostics.CodeAnalysis;
+using System.Runtime.CompilerServices;
 
 
 #if !NETSTANDARD2_0
 using System.Runtime.Intrinsics;
 using System.Runtime.Intrinsics.X86;
 #endif
 
+#if NET6_0_OR_GREATER
+using System.Runtime.Intrinsics.Arm;
+#endif
+
 namespace BitFaster.Caching.Lfu
 {
     /// <summary>
@@ -76,6 +81,12 @@ 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);
@@ -99,6 +110,12 @@ public void Increment(T value)
             {
                 IncrementAvx(value);
             }
+#if NET6_0_OR_GREATER
+            else if (isa.IsArm64Supported)
+            {
+                IncrementArm(value);
+            }
+#endif
             else
             {
                 IncrementStd(value);
@@ -329,5 +346,94 @@ private unsafe void IncrementAvx(T value)
             }
         }
 #endif
+
+#if NET6_0_OR_GREATER
+        [MethodImpl(MethodImplOptions.AggressiveOptimization | 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.AggressiveOptimization | 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
     }
 }