# 実行前提: PowerShell 7.4 以降


# $Hosts は処理対象オブジェクトの配列（ここでは仮想的なデータ）

$Hosts = 1..20 | ForEach-Object {
    [PSCustomObject]@{
        Name = "Target-Host-$_"
        Delay = Get-Random -Minimum 50 -Maximum 500 # 処理時間 (ms)
        Fail = (Get-Random -Maximum 10) -eq 1 # 10%の確率で失敗
    }
}

$MaxRetry = 2
$ThrottleLimit = 5 # CPUコア数やI/O負荷に基づき最適化

$Results = Measure-Command {
    $Hosts | ForEach-Object -Parallel {
        param($TargetHost)

        # 実行Runspace内で必要な変数を定義

        $AttemptCount = 0
        $ScriptResult = $null

        do {
            try {
                $AttemptCount++
                $LogMessage = "Processing $($TargetHost.Name) (Attempt $AttemptCount)"
                Write-Host $LogMessage

                # 仮想的なI/O処理 (CIM/WMI処理を想定)


                # 例: Get-CimInstance -ComputerName $TargetHost.Name -Query "SELECT * FROM Win32_Service"

                Start-Sleep -Milliseconds $TargetHost.Delay

                # 仮想的なエラー発生

                if ($TargetHost.Fail -and $AttemptCount -lt 2) {
                    throw "SimulatedTransientError: The service connection timed out."
                }

                $ScriptResult = [PSCustomObject]@{
                    Host = $TargetHost.Name
                    Status = "Success"
                    TotalAttempts = $AttemptCount
                    Data = "OK"
                }
                break # 成功したらループを抜ける

            } catch {

                # エラー種別判定と再試行ロジック

                $ErrorMessage = $_.Exception.Message
                if ($AttemptCount -lt $Using:MaxRetry -and $ErrorMessage -like "*Timeout*") {

                    # 一時的なエラー（Transient Error）と判断し、待機して再試行

                    Start-Sleep -Seconds 1 
                    Write-Warning "Transient error on $($TargetHost.Name). Retrying..."
                    continue # do-whileの次のループへ
                } else {

                    # 恒久的なエラーまたは再試行回数超過

                    $ScriptResult = [PSCustomObject]@{
                        Host = $TargetHost.Name
                        Status = "Failed"
                        Error = $ErrorMessage
                        TotalAttempts = $AttemptCount
                    }
                    break # ループを抜ける
                }
            }
        } while ($AttemptCount -lt $Using:MaxRetry)

        # 出力ストリームに結果を戻す

        $ScriptResult 

    } -ThrottleLimit $ThrottleLimit
}

# 結果集計

$Successful = $Results.Count | Where-Object {$_.Status -eq "Success"}
$Failed = $Results.Count | Where-Object {$_.Status -eq "Failed"}

# 計算量: O(N/T) + T_overhead (N:タスク数, T:ThrottleLimit)

Write-Host "--- SUMMARY ---"
Write-Host "Total Time: $($Results.TotalSeconds) seconds"
Write-Host "Success: $($Successful.Count), Failed: $($Failed.Count)"

# 実行前提: $LargeList は1000個のデータを持つ配列

$LargeList = 1..1000

function Test-Workload {
    param($InputObject)

    # 仮想的な軽量I/O作業

    Start-Sleep -Milliseconds 1
}

# 1. 同期処理の計測 (ベースライン)

$SyncTime = Measure-Command {
    $LargeList | ForEach-Object { Test-Workload -InputObject $_ }
}
Write-Host "同期処理時間: $($SyncTime.TotalMilliseconds) ms"

# 2. 並列処理の計測 (ThrottleLimit=10)

$ParallelTime = Measure-Command {
    $LargeList | ForEach-Object -Parallel { Test-Workload -InputObject $_ } -ThrottleLimit 10
}
Write-Host "並列処理時間 (Throttle 10): $($ParallelTime.TotalMilliseconds) ms"

# 3. 性能差の評価

$Ratio = [math]::Round($SyncTime.TotalMilliseconds / $ParallelTime.TotalMilliseconds, 2)
Write-Host "性能向上比率 (倍): $Ratio"

# 並列実行した結果をファイルに出力する際

$Results | ConvertTo-Json | Out-File -FilePath "results.json" -Encoding UTF8