PowerShell 计时器/秒表准确性

Question

我发现 System.Diagnostics.Stopwatch 类即使在很短的时间段(即 20 秒)内似乎也存在可测量的不准确性。对于编码为运行 20 秒的进程，我的进程显示耗时为 20.3+ 秒:

$elapsed = [System.Diagnostics.Stopwatch]::StartNew()
write-host "Started at $(get-date)"

for ($t=1; $t -le 20; $t++) {
    Write-Host "Elapsed Time: $($elapsed.Elapsed.ToString())"
    sleep 1
}

write-host "Ended at $(get-date)"
write-host "Total Elapsed Time: $($elapsed.Elapsed.ToString())"

    Started at 02/02/2013 15:08:43
    Elapsed Time: 00:00:00.0329924
    Elapsed Time: 00:00:01.0417435
    Elapsed Time: 00:00:02.0547547
    Elapsed Time: 00:00:03.0689716
    Elapsed Time: 00:00:04.0820497
    Elapsed Time: 00:00:05.0963413
    Elapsed Time: 00:00:06.1113915
    Elapsed Time: 00:00:07.1244044
    Elapsed Time: 00:00:08.1396105
    Elapsed Time: 00:00:09.1528952
    Elapsed Time: 00:00:10.1659905
    Elapsed Time: 00:00:11.1800884
    Elapsed Time: 00:00:12.1940009
    Elapsed Time: 00:00:13.2081824
    Elapsed Time: 00:00:14.2223585
    Elapsed Time: 00:00:15.2375023
    Elapsed Time: 00:00:16.2506360
    Elapsed Time: 00:00:17.2656845
    Elapsed Time: 00:00:18.2790676
    Elapsed Time: 00:00:19.2928700
    Ended at 02/02/2013 15:09:04
    Total Elapsed Time: 00:00:20.3080067

在 PowerShell 中使用 Stopwatch 类时是否会出现这种精度漂移？它似乎与时间跨度不成比例地增加(即 10 秒减少 0.1，20 秒减少 0.3)。我的代码有问题吗？

Answer 1

您有 20 次 1 秒的停顿，但您还有其他事情要做。有一个循环递增并测试一个变量，您可以在每次迭代中写入耗时。这些额外的事情需要时间。

这仍然有 20 秒的暂停，耗时接近 20 秒，因为 PowerShell 必须做的额外事情更少:

$elapsed = [System.Diagnostics.Stopwatch]::StartNew()
write-host "Started at $(get-date)"
sleep 20
write-host "Ended at $(get-date)"
write-host "Total Elapsed Time: $($elapsed.Elapsed.ToString())"