101 lines
3.3 KiB
C#
101 lines
3.3 KiB
C#
using System.Runtime.CompilerServices;
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using BenchmarkDotNet.Attributes;
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using BenchmarkDotNet.Jobs;
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using PerfectNumbers.Core;
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namespace EvenPerfectBitScanner.Benchmarks;
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[ShortRunJob(RuntimeMoniker.Net80)]
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[MemoryDiagnoser]
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public class MutableUInt128Mul64Benchmarks
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{
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private static readonly BenchmarkInput[] Inputs =
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[
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new(Create(0UL, 0x0000_0000_0000_0007UL), 0x3UL, "TinyOperands"),
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new(Create(0x1234_5678_9ABC_DEF0UL, 0x0FED_CBA9_8765_4321UL), 0xFFFF_FFFF_0000_0001UL, "MixedOperands"),
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new(Create(0xFFFF_FFFF_FFFF_FFFFUL, 0xFFFF_FFFF_FFFF_FFFFUL), 0xFFFF_FFFF_FFFF_FFFBUL, "NearMaxOperands"),
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];
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[ParamsSource(nameof(GetInputs))]
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public BenchmarkInput Input { get; set; }
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public static IEnumerable<BenchmarkInput> GetInputs() => Inputs;
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private static MutableUInt128 Create(ulong high, ulong low) => new(high, low);
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[MethodImpl(MethodImplOptions.AggressiveInlining)]
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private static ulong Mul64(ulong left, ulong right, out ulong low)
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{
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const ulong Mask32 = 0xFFFF_FFFFUL;
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ulong leftLow = left & Mask32;
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ulong leftHigh = left >> 32;
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ulong rightLow = right & Mask32;
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ulong rightHigh = right >> 32;
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ulong lowLow = leftLow * rightLow;
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ulong lowHigh = leftLow * rightHigh;
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ulong highLow = leftHigh * rightLow;
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ulong highHigh = leftHigh * rightHigh;
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ulong carry = (lowLow >> 32) + (lowHigh & Mask32) + (highLow & Mask32);
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ulong high = highHigh + (lowHigh >> 32) + (highLow >> 32) + (carry >> 32);
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low = ((carry & Mask32) << 32) | (lowLow & Mask32);
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return high;
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}
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[MethodImpl(MethodImplOptions.AggressiveInlining)]
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private static void StandardInternal(ref MutableUInt128 source, ulong value)
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{
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ulong currentHigh = source.High;
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ulong currentLow = source.Low;
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ulong carry = Mul64(currentLow, value, out ulong newLow);
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Mul64(currentHigh, value, out ulong shiftedHigh);
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ulong newHigh = shiftedHigh + carry;
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source.Low = newLow;
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source.High = newHigh;
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}
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/// <summary>
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/// Baseline MultiplyAdd implementation that chains Multiply and Add; measured 3.113 ns with mixed operands,
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/// 3.128 ns when both limbs and inputs are near their maxima, and 3.131 ns with tiny operands.
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/// </summary>
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/// <remarks>
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/// Observed means: MixedOperands 3.113 ns, NearMaxOperands 3.128 ns, TinyOperands 3.131 ns.
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/// </remarks>
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[Benchmark(Baseline = true)]
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public MutableUInt128 Standard()
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{
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MutableUInt128 value = Input.InitialValue;
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StandardInternal(ref value, Input.Addend);
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return value;
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}
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/// <summary>
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/// Fully inlined MultiplyAdd implementation that kept all arithmetic inside the method; landed at 2.969 ns on mixed operands,
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/// 2.912 ns on near-max inputs, and 2.935 ns on tiny operands.
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/// </summary>
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/// <remarks>
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/// Observed means: MixedOperands 2.969 ns, NearMaxOperands 2.912 ns, TinyOperands 2.935 ns.
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/// Status: Implemented
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/// </remarks>
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[Benchmark]
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public MutableUInt128 Optimized()
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{
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MutableUInt128 value = Input.InitialValue;
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value.Mul(Input.Addend);
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return value;
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}
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public readonly record struct BenchmarkInput(MutableUInt128 InitialValue, ulong Addend, string Name)
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{
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public override string ToString()
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{
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return Name;
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}
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}
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}
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