unique_speed_test.ps1

function Filter-Duplication
{
    [CmdletBinding()]
    param (
        [Parameter(ValueFromPipeline)]
        [object[]]
        $InputObject
    )
    begin
    {
        $input_values = @{} 
    }
    process
    {
        if (-not $input_values.ContainsKey($_))
        {
            $input_values.Add($_, $true)
            $_
        }
    }
}

function Measure-Unique
{
    param(
        $ScriptBlock
    )
    $result = Measure-Command $ScriptBlock

    [PSCustomObject]@{
        Script = $ScriptBlock.tostring()
        msec   = "$($result.TotalMilliseconds)"
    } | Format-List
}

$count = 100000

$list = 1..$count | foreach { Get-Random -min 0 -max 100000 }

Write-Host "sorted"

Measure-Unique { $list | Filter-Duplication | Sort-Object }
Measure-Unique { $list | Sort-Object -Unique }
Measure-Unique { $list | Sort-Object | Get-Unique }
Measure-Unique { [System.Collections.Generic.HashSet[object]]$list | Sort-Object }
Measure-Unique { [object[]][System.Collections.Generic.SortedSet[object]]$list }

Write-Host "not sorted"

Measure-Unique { $list | Filter-Duplication }
Measure-Unique { [object[]][System.Collections.Generic.HashSet[object]]$list }