まったりプログラミングぶろぐ

using System.Collections;
using System.Diagnostics;

//◆resume
//広範囲切り出ししない場合
//　参照渡しが最速
//広範囲切り出しのする場合
//　skp+takeが無難(ToAry/LstせずEnumerableで扱う前提)
//　len200未満ならAry.Cpy
//◆detail
//len200あたりを堺に、skp+takeの方が早くなる
//var iTime = 1,000,000;
// ----- cpy系 (参照含む) -----
//only for          :0.003916810000000001

//=[20]             :0.00506919
//Ary.Cpy2-18       :0.026659270000000002   // skpの2倍程速い
//Bf.BlkCpy2-18     :0.035986769999999994
//skip2-take18      :0.055729600000000004
//skip2-take18.Cnt  :0.06131551999999999
//ms read2-18       :0.07749840999999999
//skip2-take18.ToAry:0.12371009
//skip2-take18.ToLst:0.12653051
//ms sr only ctor20 :0.53210541

//=[200]              :0.0039536599999999995
//Ary.Cpy20-180       :0.03792715           // skpと大差なし
//Bf.BlkCpy20-180     :0.038147219999999996
//skip20-take180      :0.04647439999999999
//skip20-take180.Cnt  :0.06053751
//ms read20-180       :0.06210962
//ms sr only ctor200  :0.39515325999999995
//skip20-take180.ToLst:0.53726021
//skip20-take180.ToAry:0.58260523

//=[2000]               :0.004071860000000001
//skip200-take1800      :0.04412279         // 次点のCpyの5倍程速い
//skip200-take1800.Cnt  :0.05719957
//Bf.BlkCpy200-1800     :0.22781015
//Ary.Cpy200-1800       :0.23208406999999998
//ms read200-1800       :0.25393420000000005
//ms sr only ctor2000   :0.38667927
//skip200-take1800.ToLst:4.3359177099999995
//skip200-take1800.ToAry:4.411541120000001

//=[20000]              :0.00409403
//skip2000-take18000    :0.04361117         // 次点のCpyの50倍程速い
//skip2000-take18000.Cnt:0.055852250000000006
//ms sr only ctor20000  :0.42708772999999994
//Bf.BlkCpy2000-18000   :2.0283845
//Ary.Cpy2000-18000     :2.1328456
//ms read2000-18000     :2.22134107

var jTime = 10;
var iTime = 1_000_000;
Console.WriteLine($"var iTime = {iTime.ToString("#,##0")};");
Stopwatch sw;
var swList = new List();
var swAveDic = new Dictionary();

Action> 計測 = (procName, loopAct) =>
{
    //Console.WriteLine(procName);
    swList.Clear();
    for (var j = 0; j < jTime; j++)
    {
        sw = Stopwatch.StartNew();
        for (var i = 0; i < iTime; i++)
            loopAct(i);
        sw.Stop();
        swList.Add(sw.Elapsed.TotalSeconds);
        //Console.WriteLine($"{procName}:{sw.Elapsed.TotalSeconds}");
    }
    swAveDic[procName] = swList.Average();
};

計測("only for", (i) => { });

Console.WriteLine($"\n ----- cpy系 (参照含む) -----");
for (var srcLen = 20; srcLen <= 20000; srcLen *= 10)
{
    int cpySta = srcLen / 10;
    int cpyLen = srcLen / 10 * 9;
    var byAry = Enumerable.Range(0, srcLen).Select(x => (byte)x).ToArray();
    計測($"=[{srcLen}]", (i) => { var byAry2 = byAry; });
    計測($"skip{cpySta}-take{cpyLen}", (i) => { var byAry2 = byAry.Skip(cpySta).Take(cpyLen); });
    計測($"skip{cpySta}-take{cpyLen}.Cnt", (i) => { var byAry2 = byAry.Skip(cpySta).Take(cpyLen).Count(); });
    if (cpyLen <= 5000)//万でやるとかなり重い
    {
        計測($"skip{cpySta}-take{cpyLen}.ToAry", (i) => { var byAry2 = byAry.Skip(cpySta).Take(cpyLen).ToArray(); });
        計測($"skip{cpySta}-take{cpyLen}.ToLst", (i) => { var byAry2 = byAry.Skip(cpySta).Take(cpyLen).ToArray(); });
    }
    計測($"Ary.Cpy{cpySta}-{cpyLen}", (i) => {
        var byAry2 = new byte[cpyLen];
        Array.Copy(byAry, cpySta, byAry2, 0, cpyLen);
    });
    計測($"Bf.BlkCpy{cpySta}-{cpyLen}", (i) => {
        var byAry2 = new byte[cpyLen];
        Buffer.BlockCopy(byAry, cpySta, byAry2, 0, cpyLen);
    });
    計測($"ms read{cpySta}-{cpyLen}", (i) => {
        using var ms = new MemoryStream(byAry);
        var byAry2 = new byte[cpyLen];
        ms.Position = cpySta;
        ms.Read(byAry2, 0/*書かれる側の開始位置*/, cpyLen);
    });
    計測($"ms sr only ctor{srcLen}", (i) => {
        using var ms = new MemoryStream(byAry);
        using var sr = new StreamReader(ms);
    });
    //Console.WriteLine($"\n ----- orderBy fast > cpy系 -----");
    Console.WriteLine($"");
    var keyLenMax = swAveDic.Keys.Max(x => x.Length);
    foreach (var kv in swAveDic.OrderBy(x => x.Value))
        Console.WriteLine($"{kv.Key.PadRight(keyLenMax)}:{kv.Value}");
    swAveDic.Clear();
}

var procName = "オマケ◆only for, without Action";
Console.WriteLine($"\n ----- {procName} -----");
for (var j = 0; j < jTime; j++)
{
    sw = Stopwatch.StartNew();
    for (var i = 0; i < iTime; i++)
        ;
    sw.Stop();
    Console.WriteLine($"{procName}:{sw.Elapsed.TotalSeconds}");
}