bench-preview4-array-addition.ps1

$ps = Split-Path $PSHOME

$pwsh = @(
    Join-Path $ps '7-preview/pwsh.exe'
    Join-Path $ps '7/pwsh.exe'
)

$script = {
    class SizeConvert {
        static [string[]] $Suffix = 'B', 'KB', 'MB', 'GB', 'TB', 'PB', 'EB', 'ZB', 'YB'

        static [string] ToFriendlySize([long] $Length, [int] $DecimalPoints) {
            $idx = 0

            while ($Length -ge 1kb) {
                $Length /= 1kb
                $idx++
            }
            return '{0} {1}' -f [math]::Round($Length, $DecimalPoints), [SizeConvert]::Suffix[$idx]
        }
    }

    $tests = @{
        'Explicit Assignment' = {
            param($range)

            $result = foreach ($i in $range) {
                $i
            }
        }
        'List<T>.Add(T)' = {
            param($range)

            $result = [Collections.Generic.List[int]]::new()
            foreach ($i in $range) {
                $result.Add($i)
            }
        }
        'Array addition (+=)' = {
            param($range)

            $result = @()
            foreach ($i in $range) {
                $result += $i
            }
        }
    }

    5000, 10000, 50000, 100000 | ForEach-Object {
        $range = [System.Linq.Enumerable]::Range(1, $_)
        foreach ($test in $tests.GetEnumerator()) {
            $before = [datetime]::Now
            $memBefore = [GC]::GetTotalAllocatedBytes($true)
            $test.Value.Invoke($range)
            $span = [datetime]::Now - $before
            $consumption = [SizeConvert]::ToFriendlySize(
                [GC]::GetTotalAllocatedBytes($true) - $memBefore, 2)

            [pscustomobject]@{
                PSVersion         = $PSVersionTable['PSVersion']
                CollectionSize    = $_
                Test              = $test.Key
                TotalMilliseconds = [math]::Round($span.TotalMilliseconds, 2)
                Allocated         = $consumption
            }

            [GC]::Collect()
            [GC]::WaitForPendingFinalizers()
        }
    }
}

$results = $pwsh | ForEach-Object { & $_ -NoProfile -NonInteractive -OutputFormat XML -Command $script.ToString() }
$results | Group-Object CollectionSize | ForEach-Object {
    $groupResult = $_.Group | Sort-Object TotalMilliseconds
    $groupResult | Format-Table -GroupBy CollectionSize @(
        'PSVersion'
        'Test'
        @{
            Name       = 'Allocated'
            Expression = 'Allocated'
            Alignment  = 'Right'
        }
        'TotalMilliseconds'
        @{
            Name       = 'RelativeSpeed'
            Expression = {
                [math]::Round($_.TotalMilliseconds / $groupResult[0].TotalMilliseconds, 2).ToString() + 'x'
            }
        }
    )
}

results.md

   CollectionSize: 5000

PSVersion       Test                Allocated TotalMilliseconds RelativeSpeed
---------       ----                --------- ----------------- -------------
7.5.0-preview.4 Explicit Assignment    705 KB              3.00 1x
7.4.5           Explicit Assignment    635 KB              3.27 1.09x
7.4.5           List<T>.Add(T)           3 MB              8.87 2.96x
7.5.0-preview.4 List<T>.Add(T)           4 MB             21.33 7.11x
7.5.0-preview.4 Array addition (+=)     96 MB             21.92 7.31x
7.4.5           Array addition (+=)    381 MB            420.24 140.08x


   CollectionSize: 10000

PSVersion       Test                Allocated TotalMilliseconds RelativeSpeed
---------       ----                --------- ----------------- -------------
7.4.5           Explicit Assignment    577 KB              0.85 1x
7.5.0-preview.4 Explicit Assignment    577 KB              1.07 1.26x
7.5.0-preview.4 List<T>.Add(T)           6 MB              4.29 5.05x
7.4.5           List<T>.Add(T)           6 MB              6.34 7.46x
7.5.0-preview.4 Array addition (+=)    382 MB             89.75 105.59x
7.4.5           Array addition (+=)      1 GB           1301.72 1531.44x


   CollectionSize: 50000

PSVersion       Test                Allocated TotalMilliseconds RelativeSpeed
---------       ----                --------- ----------------- -------------
7.4.5           Explicit Assignment      3 MB              3.60 1x
7.5.0-preview.4 Explicit Assignment      3 MB              3.76 1.04x
7.4.5           List<T>.Add(T)          28 MB             14.03 3.9x
7.5.0-preview.4 List<T>.Add(T)          28 MB             23.52 6.53x
7.5.0-preview.4 Array addition (+=)      9 GB          11997.76 3332.71x
7.4.5           Array addition (+=)     37 GB          38094.31 10581.75x


   CollectionSize: 100000

PSVersion       Test                Allocated TotalMilliseconds RelativeSpeed
---------       ----                --------- ----------------- -------------
7.4.5           Explicit Assignment      5 MB              5.23 1x
7.5.0-preview.4 Explicit Assignment      5 MB              8.71 1.67x
7.4.5           List<T>.Add(T)          55 MB             24.42 4.67x
7.5.0-preview.4 List<T>.Add(T)          55 MB             55.88 10.68x
7.5.0-preview.4 Array addition (+=)     37 GB          19783.15 3782.63x
7.4.5           Array addition (+=)    147 GB         124153.31 23738.68x