public class FlightPriceClass
{
    /// <summary>
    /// 航司二字碼 如 中國國際航空股份有限公司：CA
    /// </summary>
    public string Airline { get; set; }
    /// <summary>
    /// 起始機場三字碼 如 上海虹橋國際機場：SHA
    /// </summary>
    public string Start { get; set; }
    /// <summary>
    /// 抵達機場三字碼 如 北京首都國際機場：PEK
    /// </summary>
    public string End { get; set; }
    /// <summary>
    /// 航班號 如 CA0001
    /// </summary>
    public string FlightNo { get; set; }
    /// <summary>
    /// 艙位代碼 如 Y
    /// </summary>
    public string Cabin { get; set; }
    /// <summary>
    /// 價格 單位：元
    /// </summary>
    public decimal Price { get; set; }
    /// <summary>
    /// 起飛日期 如 2017-01-01
    /// </summary>
    public DateOnly DepDate { get; set; }
    /// <summary>
    /// 起飛時間 如 08:00
    /// </summary>
    public TimeOnly DepTime { get; set; }
    /// <summary>
    /// 抵達日期 如 2017-01-01
    /// </summary>
    public DateOnly ArrDate { get; set; }
    /// <summary>
    /// 抵達時間 如 08:00
    /// </summary>
    public TimeOnly ArrTime { get; set; }
}

// 隨機預先生成100W的數(shù)據(jù) 避免計算邏輯導致結果不準確
public static readonly FlightPriceClass[] FlightPrices = Enumerable.Range(0,
        100_0000
    ).Select(index =>
        new FlightPriceClass
        {
            Airline = $"C{(char)(index % 26 + 'A')}",
            Start = $"SH{(char)(index % 26 + 'A')}",
            End = $"PE{(char)(index % 26 + 'A')}",
            FlightNo = $"{index % 1000:0000}",
            Cabin = $"{(char)(index % 26 + 'A')}",
            Price = index % 1000,
            DepDate = DateOnly.FromDateTime(BaseTime.AddHours(index)),
            DepTime = TimeOnly.FromDateTime(BaseTime.AddHours(index)),
            ArrDate = DateOnly.FromDateTime(BaseTime.AddHours(3 + index)),
            ArrTime = TimeOnly.FromDateTime(BaseTime.AddHours(3 + index)),
        }).ToArray();
// 使用類來存儲
[Benchmakr]
public FlightPriceClass[] GetClassStore()
{
    var arrays = new FlightPriceClass[FlightPrices.Length];
    for (int i = 0; i < FlightPrices.Length; i++)
    {
        var item = FlightPrices[i];
        arrays[i] = new FlightPriceClass
        {
            Airline = item.Airline,
            Start = item.Start,
            End = item.End,
            FlightNo = item.FlightNo,
            Cabin = item.Cabin,
            Price = item.Price,
            DepDate = item.DepDate,
            DepTime = item.DepTime,
            ArrDate = item.ArrDate,
            ArrTime = item.ArrTime
        };
    }
    return arrays;
}

[StructLayout(LayoutKind.Auto)]
public struct FlightPriceStruct
{
    // 屬性與類一致
    ......
}

// 跳過本地變量初始化
[SkipLocalsInit]
// 調整布局方式 使用Explicit自定義布局
[StructLayout(LayoutKind.Explicit, CharSet = CharSet.Unicode)]
public struct FlightPriceStructExplicit
{
    // 需要手動指定偏移量
    [FieldOffset(0)]
    // 航司使用兩個字符存儲
    public unsafe fixed char Airline[2];
    // 由于航司使用了4byte 所以起始機場偏移4byte
    [FieldOffset(4)]
    public unsafe fixed char Start[3];
    // 同理起始機場使用6byte 偏移10byte
    [FieldOffset(10)]
    public unsafe fixed char End[3];
    [FieldOffset(16)]
    public unsafe fixed char FlightNo[4];
    [FieldOffset(24)]
    public unsafe fixed char Cabin[2];
    // decimal 16byte
    [FieldOffset(28)]
    public decimal Price;
    // DateOnly 4byte
    [FieldOffset(44)]
    public DateOnly DepDate;
    // TimeOnly 8byte
    [FieldOffset(48)]
    public TimeOnly DepTime;
    [FieldOffset(56)]
    public DateOnly ArrDate;
    [FieldOffset(60)]
    public TimeOnly ArrTime;
}

// 用于設置string值的擴展方法
[MethodImpl(MethodImplOptions.AggressiveInlining)]  
public static unsafe void SetTo(this string str, char* dest)  
{  
    fixed (char* ptr = str)  
    {  
        Unsafe.CopyBlock(dest, ptr, (uint)(Unsafe.SizeOf<char>() * str.Length));  
    }  
}
// Benchmark的方法
public static unsafe FlightPriceStructExplicit[] GetStructStoreStructExplicit()  
{  
    var arrays = new FlightPriceStructExplicit[FlightPrices.Length];  
    for (int i = 0; i < FlightPrices.Length; i++)  
    {  
        ref var item = ref FlightPrices[i];  
        arrays[i] = new FlightPriceStructExplicit  
        {  
            Price = item.Price,  
            DepDate = item.DepDate,  
            DepTime = item.DepTime,  
            ArrDate = item.ArrDate,  
            ArrTime = item.ArrTime  
        };  
        ref var val = ref arrays[i];  
        // 需要先fixed 然后再賦值
        fixed (char* airline = val.Airline)  
        fixed (char* start = val.Start)  
        fixed (char* end = val.End)  
        fixed (char* flightNo = val.FlightNo)  
        fixed (char* cabin = val.Cabin)  
        {  
            item.Airline.SetTo(airline);  
            item.Start.SetTo(start);  
            item.End.SetTo(end);  
            item.FlightNo.SetTo(flightNo);  
            item.Cabin.SetTo(cabin);  
        }  
    }  
    return arrays;  
}

// 分配非托管內存 
// 傳參是所需要分配的字節(jié)數(shù)
// 返回值是指向內存的指針
IntPtr Marshal.AllocHGlobal(int cb);

// 釋放分配的非托管內存
// 傳參是由Marshal分配內存的指針地址
void Marshal.FreeHGlobal(IntPtr hglobal);

// 定義了out ptr參數(shù)，用于將指針傳回
public static unsafe int GetStructStoreUnManageMemory(out IntPtr ptr)  
{  
    // 使用AllocHGlobal分配內存，大小使用SizeOf計算結構體大小乘需要的數(shù)量
    var unManagerPtr = Marshal.AllocHGlobal(Unsafe.SizeOf<FlightPriceStructExplicit>() * FlightPrices.Length);  
    ptr = unManagerPtr;  
    // 將內存空間指派給FlightPriceStructExplicit數(shù)組使用
    var arrays = new Span<FlightPriceStructExplicit>(unManagerPtr.ToPointer(), FlightPrices.Length);  
    for (int i = 0; i < FlightPrices.Length; i++)  
    {  
        ref var item = ref FlightPrices[i];  
        arrays[i] = new FlightPriceStructExplicit  
        {  
            Price = item.Price,  
            DepDate = item.DepDate,  
            DepTime = item.DepTime,  
            ArrDate = item.ArrDate,  
            ArrTime = item.ArrTime  
        };  
        ref var val = ref arrays[i];  
        fixed (char* airline = val.Airline)  
        fixed (char* start = val.Start)  
        fixed (char* end = val.End)  
        fixed (char* flightNo = val.FlightNo)  
        fixed (char* cabin = val.Cabin)  
        {  
            item.Airline.SetTo(airline);  
            item.Start.SetTo(start);  
            item.End.SetTo(end);  
            item.FlightNo.SetTo(flightNo);  
            item.Cabin.SetTo(cabin);  
        }  
    }  
    // 返回長度
    return arrays.Length;  
}

// 切記，非托管內存不使用的時候 需要手動釋放
[Benchmark]  
public void GetStructStoreUnManageMemory()  
{  
    _ = FlightPriceCreate.GetStructStoreUnManageMemory(out var ptr);  
    // 釋放非托管內存
    Marshal.FreeHGlobal(ptr);  
}

[StructLayout(LayoutKind.Explicit, CharSet = CharSet.Unicode)]
[SkipLocalsInit]
public struct FlightPriceStructExplicit
{
	// 使用byte標識航司  byte范圍0~255
	[FieldOffset(0)]
	public byte Airline;
	// 使用無符號整形表示起抵機場和航班號 2^16次方
	[FieldOffset(1)]
	public UInt16 Start;
	[FieldOffset(3)]
	public UInt16 End;
	[FieldOffset(5)]
	public UInt16 FlightNo;
	[FieldOffset(7)]
	public byte Cabin;
	// 不使用decimal 價格精確到分存儲
	[FieldOffset(8)]
	public long PriceFen;
	// 使用時間戳替代
	[FieldOffset(16)]
	public long DepTime;
	[FieldOffset(24)]
	public long ArrTime;
}

// 類和結構體定義的方法 當然實際中的篩選可能更加復雜
// 比較航司
public bool EqulasAirline(string airline)  
{  
    return Airline == airline;  
}  
// 比較起飛機場
public bool EqualsStart(string start)  
{  
    return Start == start;  
}  
// 比較抵達機場
public bool EqualsEnd(string end)  
{  
    return End == end;  
}
// 比較航班號
public bool EqualsFlightNo(string flightNo)  
{  
    return FlightNo == flightNo;  
}
// 價格是否小于指定值
public bool IsPriceLess(decimal min)  
{  
    return Price < min;  
}
// 對于Explicit結構體 定義了EqualsSpan方法
[MethodImpl(MethodImplOptions.AggressiveInlining)]  
public static unsafe bool SpanEquals(this string str, char* dest, int length)  
{  
    // 使用span來比較兩個數(shù)組
    return new Span<char>(dest, length).SequenceEqual(str.AsSpan());  
}

// 實現(xiàn)的方法如下所示
public static unsafe bool EqualsAirline(FlightPriceStructExplicit item, string airline)  
{  
    // 傳需要比較的長度
    return airline.SpanEquals(item.Airline, 2);  
}
// 下面的方式類似，不再贅述
public static unsafe bool EqualsStart(FlightPriceStructExplicit item, string start)  
{  
    return start.SpanEquals(item.Start, 3);  
}  
public static unsafe bool EqualsEnd(FlightPriceStructExplicit item, string end)  
{  
    return end.SpanEquals(item.End, 3);  
}  
public static unsafe bool EqualsFlightNo(FlightPriceStructExplicit item, string flightNo)  
{  
    return flightNo.SpanEquals(item.FlightNo, 4);  
}  
public static unsafe bool EqualsCabin(FlightPriceStructExplicit item, string cabin)  
{  
    return cabin.SpanEquals(item.Cabin, 2);  
}  
public static bool IsPriceLess(FlightPriceStructExplicit item, decimal min)  
{  
    return item.Price < min;  
}

// 將需要的數(shù)據(jù)初始化好  避免對測試造成影響
private static readonly FlightPriceClass[] FlightPrices = FlightPriceCreate.GetClassStore();  
private static readonly FlightPriceStruct[] FlightPricesStruct = FlightPriceCreate.GetStructStore();  
private static readonly FlightPriceStructUninitialized[] FlightPricesStructUninitialized =  
    FlightPriceCreate.GetStructStoreUninitializedArray();  
private static readonly FlightPriceStructExplicit[] FlightPricesStructExplicit =  
    FlightPriceCreate.GetStructStoreStructExplicit(); 
// 非托管內存比較特殊 只需要存儲指針地址即可
private static IntPtr _unManagerPtr;  
private static readonly int FlightPricesStructExplicitUnManageMemoryLength =  
    FlightPriceCreate.GetStructStoreUnManageMemory(out _unManagerPtr);  
[Benchmark(Baseline = true)]  
public int GetClassStore()  
{  
    var caAirline = 0;  
    var shaStart = 0;  
    var peaStart = 0;  
    var ca0001FlightNo = 0;  
    var priceLess500 = 0;  
    for (int i = 0; i < FlightPrices.Length; i++)  
    {  
        // 簡單的篩選數(shù)據(jù)
        var item = FlightPrices[i];  
        if (item.EqualsAirline("CA"))caAirline++;  
        if (item.EqualsStart("SHA"))shaStart++;  
        if (item.EqualsEnd("PEA"))peaStart++;  
        if (item.EqualsFlightNo("0001"))ca0001FlightNo++;  
        if (item.IsPriceLess(500))priceLess500++;  
    }  
    Debug.WriteLine($"{caAirline},{shaStart},{peaStart},{ca0001FlightNo},{priceLess500}");  
    return caAirline + shaStart + peaStart + ca0001FlightNo + priceLess500;  
}  
[Benchmark]  
public int GetStructStore()  
{  
    var caAirline = 0;  
    var shaStart = 0;  
    var peaStart = 0;  
    var ca0001FlightNo = 0;  
    var priceLess500 = 0;  
    for (int i = 0; i < FlightPricesStruct.Length; i++)  
    {  
        var item = FlightPricesStruct[i];  
        if (item.EqualsAirline("CA"))caAirline++;  
        if (item.EqualsStart("SHA"))shaStart++;  
        if (item.EqualsEnd("PEA"))peaStart++;  
        if (item.EqualsFlightNo("0001"))ca0001FlightNo++;  
        if (item.IsPriceLess(500))priceLess500++;  
    }  
    Debug.WriteLine($"{caAirline},{shaStart},{peaStart},{ca0001FlightNo},{priceLess500}");  
    return caAirline + shaStart + peaStart + ca0001FlightNo + priceLess500;  
}  
[Benchmark]  
public int GetFlightPricesStructExplicit()  
{  
    var caAirline = 0;  
    var shaStart = 0;  
    var peaStart = 0;  
    var ca0001FlightNo = 0;  
    var priceLess500 = 0;  
    for (int i = 0; i < FlightPricesStructExplicit.Length; i++)  
    {  
        var item = FlightPricesStructExplicit[i];  
        if (FlightPriceStructExplicit.EqualsAirline(item,"CA"))caAirline++;  
        if (FlightPriceStructExplicit.EqualsStart(item,"SHA"))shaStart++;  
        if (FlightPriceStructExplicit.EqualsEnd(item,"PEA"))peaStart++;  
        if (FlightPriceStructExplicit.EqualsFlightNo(item,"0001"))ca0001FlightNo++;  
        if (FlightPriceStructExplicit.IsPriceLess(item,500))priceLess500++;  
    }  
    Debug.WriteLine($"{caAirline},{shaStart},{peaStart},{ca0001FlightNo},{priceLess500}");  
    return caAirline + shaStart + peaStart + ca0001FlightNo + priceLess500;  
}  
[Benchmark]  
public unsafe int GetFlightPricesStructExplicitUnManageMemory()  
{  
    var caAirline = 0;  
    var shaStart = 0;  
    var peaStart = 0;  
    var ca0001FlightNo = 0;  
    var priceLess500 = 0;  
    var arrays = new Span<FlightPriceStructExplicit>(_unManagerPtr.ToPointer(), FlightPricesStructExplicitUnManageMemoryLength);  
    for (int i = 0; i < arrays.Length; i++)  
    {  
        var item = arrays[i];  
        if (FlightPriceStructExplicit.EqualsAirline(item,"CA"))caAirline++;  
        if (FlightPriceStructExplicit.EqualsStart(item,"SHA"))shaStart++;  
        if (FlightPriceStructExplicit.EqualsEnd(item,"PEA"))peaStart++;  
        if (FlightPriceStructExplicit.EqualsFlightNo(item,"0001"))ca0001FlightNo++;  
        if (FlightPriceStructExplicit.IsPriceLess(item,500))priceLess500++;  
    }  
    Debug.WriteLine($"{caAirline},{shaStart},{peaStart},{ca0001FlightNo},{priceLess500}");  
    return caAirline + shaStart + peaStart + ca0001FlightNo + priceLess500;  
}

// 改造比較方法，使其支持引用傳遞
// 加入ref
public static unsafe bool EqualsAirlineRef(ref FlightPriceStructExplicit item, string airline)  
{  
    // 傳遞的是引用 需要fixed獲取指針
    fixed(char* ptr = item.Airline)  
    {  
        return airline.SpanEquals(ptr, 2);  
    }  
}

// Benchmark內部代碼也修改為引用傳遞
[Benchmark]  
public unsafe int GetStructStoreUnManageMemoryRef()  
{  
    var caAirline = 0;  
    var shaStart = 0;  
    var peaStart = 0;  
    var ca0001FlightNo = 0;  
    var priceLess500 = 0;  
    var arrays = new Span<FlightPriceStructExplicit>(_unManagerPtr.ToPointer(), FlightPricesStructExplicitUnManageMemoryLength);  
    for (int i = 0; i < arrays.Length; i++)  
    {  
        // 從數(shù)組里面拿直接引用
        ref var item = ref arrays[i];
        // 傳參也直接傳遞引用
        if (FlightPriceStructExplicit.EqualsAirlineRef(ref item,"CA"))caAirline++;  
        if (FlightPriceStructExplicit.EqualsStartRef(ref item,"SHA"))shaStart++;  
        if (FlightPriceStructExplicit.EqualsEndRef(ref item,"PEA"))peaStart++;  
        if (FlightPriceStructExplicit.EqualsFlightNoRef(ref item,"0001"))ca0001FlightNo++;  
        if (FlightPriceStructExplicit.IsPriceLessRef(ref item,500))priceLess500++;  
    }  
    Debug.WriteLine($"{caAirline},{shaStart},{peaStart},{ca0001FlightNo},{priceLess500}");  
    return caAirline + shaStart + peaStart + ca0001FlightNo + priceLess500;  
}

[HardwareCounters(
    HardwareCounter.LlcMisses, // 緩存未命中次數(shù)  
    HardwareCounter.LlcReference)]  // 解引用次數(shù)
public class SpeedBench : IDisposable  
{
    ......
}