‫بهینه‌سازی عملکرد در برنامه‌نویسی NET.: چالش یک میلیارد سطر

using var reader = new StreamReader(file.FullName);
var data = new Dictionary<string, Measurement>();
while (!reader.EndOfStream)
{
    var stationParts = (await reader.ReadLineAsync())?.Split(';');
    var measurement = data.TryGetValue(stationParts[0], out var m) ? m : new Measurement();
    var value = double.Parse(stationParts[1]);
    measurement.Sum += value;
    measurement.Min = Math.Min(measurement.Min, value);
    measurement.Max = Math.Max(measurement.Max, value);
    measurement.Count++;
    data[stationParts[0]] = measurement;
}

Span<byte> buffer = new byte[1024 * 512];
var data = new Dictionary<string, Measurement>();
using var reader = file.OpenRead();
int bufferOffsetStart = 0;
while (reader.Read(buffer) is int numberRead)
{
    if(numberRead == 0)
        break;

    if(numberRead < buffer.Length)
        buffer = buffer[..numberRead];

    if (buffer[bufferOffsetStart] == 239)
        bufferOffsetStart+=3; //SKIP BOM

    while(buffer.Slice(bufferOffsetStart).IndexOf((byte)'\n') is int newLineIndex and > -1)
    {
        var line = buffer.Slice(bufferOffsetStart, newLineIndex);
        bufferOffsetStart += newLineIndex + 1;

        var seperatorIndex = line.IndexOf((byte)';');

        var name = System.Text.Encoding.UTF8.GetString(line[..seperatorIndex]);
        var measurement = data.TryGetValue(name, out var m) ? m : new Measurement();

        var value = double.Parse(System.Text.Encoding.UTF8.GetString(line[(seperatorIndex + 1)..]));

        measurement.Sum += value;
        measurement.Min = measurement.Min < value ? measurement.Min : value;
        measurement.Max = measurement.Max > value ? measurement.Max : value;
        measurement.Count++;

        data[name] = measurement;
    }
    reader.Seek(bufferOffsetStart - buffer.Length, SeekOrigin.Current);
    bufferOffsetStart = 0;
}

public static class FastParser
{
    public const byte sign = (byte)'-';
    public const byte dot = (byte)'.';
    public const byte digitOffset = (byte)'0';

    public static int TempAsInt(ReadOnlySpan<byte> chunk)
    {
        bool negative = chunk[0] == sign;
        int off = negative ? 1 : 0;
        int temp = chunk[off++] - digitOffset;
        if (chunk[off] != dot)
            temp = 10 * temp + chunk[off++] - digitOffset;
        off++; //Skip the '.'
        temp = 10 * temp + chunk[off] - digitOffset;
        return negative ? -temp : temp;
    }
}

ref var measurement = ref CollectionsMarshal.GetValueRefOrAddDefault(data, stationName, out bool exists);
if(!exists)
    measurement = new Measurement(); // مقداردهی اولیه در صورت عدم وجود

var value = FastParser.TempAsInt(temperatureSpan);
measurement.Sum += value;
measurement.Min = Math.Min(measurement.Min, value);
measurement.Max = Math.Max(measurement.Max, value);
measurement.Count++;

public static long GenerateKey(ReadOnlySpan<byte> chunk)
{
    long key = chunk.Length << 64;
    for (int i = 0, l = chunk.Length; i < l && i < 7; i++)
        key += chunk[i] << (56 - i * 8);
    return key;
}