PowerShellのジョブ関連コマンドとタスクの並列実行の解説

> Get-Job | Wait-Job

Remove-Job *
#Test timer start
$start_time = (Get-Date)
Start-Job -ScriptBlock { sleep 9; Write-Host "Hello myJob1."; } -Name "myJob1"
Start-Job -ScriptBlock { sleep 5; Write-Host "Hello myJob2."; } -Name "myJob2"
$taskCount = 2
while($taskCount -gt 0)
{
 foreach($job in Get-Job)
 {
  $state = [string]$job.State
  if($state -eq "Completed")
  { 
   Write-Host($job.Name + " Completed")
   Receive-Job $job
   $taskCount--
   Remove-Job $job
  }
 }
 sleep 1
}
"All tasks have been completed" 
# derive the time the task ran
(New-TimeSpan $start_time).totalseconds

function Run-Tasks
{
 Param
 (
  $taskArr,
  $parallelcount=1
 )
 #Test timer starts
 $startTime = (Get-Date)
  #Remove all existing background tasks from this session
 Remove-Job *
 # Use the variable $taskCount to store the number of tasks that have not yet been executed
 $taskCount = $taskArr.Length
 
 # Determine if the set number of parallel tasks exceeds the number of tasks in the current task queue
 if($parallelCount -gt $taskArr.Length)
 {
  $parallelCount = $taskArr.Length
 }
 # Start the initial tasks
 foreach($i in 1... $parallelCount)
 {
  Start-Job $taskArr[$i - 1] -Name "task$i"
 }
 #Tasks that start after the initial task completes
 $nextIndex = $parallelCount
 #keep polling the created tasks while there are still tasks in the task queue, and delete a background task when it finishes
 #then take the next task from the task queue for execution, and wait for all tasks to finish executing.
 while(($nextIndex -lt $taskArr.Length) -or ($taskCount -gt 0))
 {
  foreach($job in Get-Job)
  {
   $state = [string]$job.State
   if($state -eq "Completed")
   { 
    Write-Host($job.Name + " Completed with the following result:")
    Receive-Job $job
    Remove-Job $job
    $taskCount--
    if($nextIndex -lt $taskArr.Length)
    { 
     $taskNumber = $nextIndex + 1
     Start-Job $taskArr[$nextIndex] -Name "task$taskNumber"
     $nextIndex++
    }
   }
  }
  sleep 1
 }
 "All tasks have been completed"
 # derive the time the task ran
 (New-TimeSpan $startTime).totalseconds
}

#define 6 tasks
$task1 = {sleep 12; Write-Host "Hello myJob1."; }
$task2 = {sleep 5; Write-Host "Hello myJob2."; }
$task3 = {sleep 8; Write-Host "Hello myJob3."; }
$task4 = {sleep 3; Write-Host "Hello myJob4."; }
$task5 = {sleep 20; Write-Host "Hello myJob5."; }
$task6 = {sleep 15; Write-Host "Hello myJob6."; } 
# write 6 tasks to an array as a task queue
$taskArr = $task1, $task2, $task3, $task4, $task5, $task6
#Run the tasks in the array, allowing 4 tasks to run simultaneously
Run-Tasks -taskArr $taskArr -parallelcount 4