Measure-ScriptBlock

I recently came over an interesting thread on LinkedIn where they talked about how to count lines in a CSV. A lot of good code examples where posted, where they tried to optimize for speed and memory consumption. I decided to try out some ideas of my own, but as I often do, I got sidetracked into building a function to easily perform measurements of code blocks instead.

“Wait a minute” I hear you say, “there already exist a command for that!”. True, Measure-Command is golden, but what I needed was something that was able to measure memory and cpu as well as time. So I created Measure-ScriptBlock. It uses Measure-Command internally but also measures memory consumption and CPU time while the code is executing. To top it all of, I added the option of specifying how many iterations of the code you want to run, and whether you want the mean value automatically calculated or not.

If you have any comments, or ideas for future improvement, please let me know!

	function Measure-ScriptBlock {
	<#
	.SYNOPSIS
	Measure time, memory consumption and CPU time for a block of code to execute.

	.DESCRIPTION
	Measure time, memory consumption and CPU time for a block of code to execute.
	This function is using Measure-Command internally, but is also trying to record how much memory and CPU time the code uses during execution.

	.EXAMPLE
	Measure-ScriptBlock -ScriptBlock {Get-ChildItem -Recurse} -Iteration 10 -TimeUnit 'Milliseconds' -SizeUnit 'KB'
	Run the code 10 times, formatting the mean values in Milliseconds and KB.

	.EXAMPLE
	Measure-ScriptBlock -ScriptBlock {Get-ChildItem -Recurse} -Iteration 10 -TimeUnit 'Milliseconds' -SizeUnit 'KB' -CalculateMeans:$false
	Run the same measurements are the above example, except skip calculating the mean value for the measurements taken.

	.EXAMPLE
	Measure-ScriptBlock -ScriptBlock $codeArray -Iteration 10 \| Format-Table
	Run an array of script blocks 10 times, formatting the output in a table.

	.OUTPUTS
	System.Management.Automation.PSCustomObject

	.NOTES
	Author: Øyvind Kallstad
	Date: 28.10.2014
	Version: 1.0
	#>
	[CmdletBinding()]
	param (
	# Code to measure
	[Parameter(Position = 0, Mandatory = $true)]
	[ValidateNotNullOrEmpty()]
	[ScriptBlock[]] $ScriptBlock,

	# Set how many times you want to execute each ScriptBlock
	[Parameter()]
	[int32] $Iterations = 1,

	# Pause, in milliseconds, between each iteration
	[Parameter()]
	[int32] $Pause = 600,

	# Use this switch to control whether the mean values of each iteration should be calculated or not
	[Parameter()]
	[switch] $CalculateMeans = $true,

	# Customize the unit used for timings. Valid values are 'Hours','Minutes','Seconds' and 'Milliseconds'.
	[Parameter()]
	[ValidateSet('Hours','Minutes','Seconds','Milliseconds')]
	[string] $TimeUnit = 'Seconds',

	# Customize the unit of size. Valid values are 'KB','MB','GB' and 'TB'.
	[Parameter()]
	[ValidateSet('KB','MB','GB','TB')]
	[string] $SizeUnit = 'MB'
	)

	# initializing our counters – used by Write-Progress
	$arrayLength = $ScriptBlock.Count
	$totalCount = 0
	$arrayCount = 0

	# perform garbage collecting
	[gc]::Collect()
	[gc]::WaitForPendingFinalizers()
	[gc]::Collect()

	Start-Sleep –Seconds 1

	foreach ($script in $ScriptBlock) {
	$arrayCount++

	for ($i = 1; $i -le $Iterations; $i++) {

	# write progress bar
	$totalCount++
	Write-Progress –Activity 'Measuring' –Status "Executing ScriptBlock $($arrayCount)" –CurrentOperation "Iteration $($i)" –PercentComplete (($totalCount/($arrayLength$iterations))100)

	# perform garbage collecting
	[gc]::Collect()
	[gc]::WaitForPendingFinalizers()
	[gc]::Collect()

	# get current memory usage for current process
	$memBefore = [System.Diagnostics.Process]::GetCurrentProcess().PrivateMemorySize64

	# get current processor time for current process
	$cpuTimeBefore = [System.Diagnostics.Process]::GetCurrentProcess().TotalProcessorTime

	# run code
	$ttr = Measure-Command {
	$result = Invoke-Command –ScriptBlock $script
	} \| Select-Object –ExpandProperty "Total$($TimeUnit)"
	$ttrArray += ,($ttr)

	# get current processor time for current process
	$cpuTimeAfter = [System.Diagnostics.Process]::GetCurrentProcess().TotalProcessorTime

	# get current memory usage for current process
	$memAfter = [System.Diagnostics.Process]::GetCurrentProcess().PrivateMemorySize64

	# do calculations
	$cpuTime = ($cpuTimeAfter \| Select-Object –ExpandProperty "Total$($TimeUnit)") – ($cpuTimeBefore \| Select-Object –ExpandProperty "Total$($TimeUnit)")
	$cpuTimeArray += ,($cpuTime)
	$memDifference = ($memAfter/"1$SizeUnit") – ($memBefore/"1$SizeUnit")
	if ($memDifference -lt 0) {$memDifference = 0} # just making sure we don't get a negative value
	$memDifferenceArray += ,($memDifference)

	if (-not($CalculateMeans)) {
	# if we don't want the calculated means we can
	# write the output to the pipeline after each iteration
	Write-Output ([PSCustomObject] [Ordered] @{
	'ScriptBlock' = $script
	'Result' = $result
	'Iteration' = $i
	"Memory ($($SizeUnit))" = ('{0:N0}' -f $memDifference)
	"Processor Time ($($TimeUnit))" = ('{0:N2}' -f $cpuTime)
	"Time To Run ($($TimeUnit))" = ('{0:N2}' -f $ttr)
	})
	}

	# a small pause before next iteration
	Start-Sleep –Milliseconds $Pause
	}

	# if we want the calculated means of our measurements,
	# we need to wait until all iterations are complete before
	# writing the output to the pipeline
	if ($CalculateMeans) {
	# create output object
	Write-Output ([PSCustomObject] [Ordered] @{
	'ScriptBlock' = $script
	'Result' = $result
	'Iterations' = $Iterations
	"Memory ($($SizeUnit))" = ('{0:N0}' -f ($memDifferenceArray \| Measure-Object –Average \| Select-Object –ExpandProperty Average))
	"Processor Time ($($TimeUnit))" = ('{0:N2}' -f ($cpuTimeArray \| Measure-Object –Average \| Select-Object –ExpandProperty Average))
	"Time To Run ($($TimeUnit))" = ('{0:N2}' -f ($ttrArray \| Measure-Object –Average \| Select-Object –ExpandProperty Average))
	})

	# reset the arrays
	Remove-Variable –Name memDifferenceArray,cpuTimeArray,ttrArray –ErrorAction SilentlyContinue
	}

	}

	# perform garbage collecting
	[gc]::Collect()
	[gc]::WaitForPendingFinalizers()
	[gc]::Collect()
	}