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124 lines
4.1 KiB
Markdown
124 lines
4.1 KiB
Markdown
*measure-MergeSort.ps1*
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================
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This PowerShell script measures the speed of the MergeSort algorithm.
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MergeSort is an efficient, general-purpose, and comparison-based sorting algorithm.
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Most implementations produce a stable sort, which means that the order of equal elements
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is the same in the input and output. Merge sort is a divide-and-conquer algorithm that
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was invented by John von Neumann in 1945. A detailed description and analysis of bottom-up
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merge sort appeared in a report by Goldstine and von Neumann as early as 1948.
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Parameters
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----------
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```powershell
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PS> ./measure-MergeSort.ps1 [[-numIntegers] <Int32>] [<CommonParameters>]
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-numIntegers <Int32>
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Specifies the number of integers to sort
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Required? false
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Position? 1
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Default value 1000
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Accept pipeline input? false
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Accept wildcard characters? false
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[<CommonParameters>]
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This script supports the common parameters: Verbose, Debug, ErrorAction, ErrorVariable, WarningAction,
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WarningVariable, OutBuffer, PipelineVariable, and OutVariable.
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```
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Example
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-------
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```powershell
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PS> ./measure-MergeSort.ps1
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🧭 0.378 sec to sorting 1000 integers by MergeSort
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```
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Notes
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-----
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Author: Markus Fleschutz | License: CC0
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Related Links
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-------------
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https://github.com/fleschutz/PowerShell
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Script Content
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--------------
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```powershell
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<#
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.SYNOPSIS
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Measures the speed of MergeSort
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.DESCRIPTION
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This PowerShell script measures the speed of the MergeSort algorithm.
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MergeSort is an efficient, general-purpose, and comparison-based sorting algorithm.
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Most implementations produce a stable sort, which means that the order of equal elements
|
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is the same in the input and output. Merge sort is a divide-and-conquer algorithm that
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was invented by John von Neumann in 1945. A detailed description and analysis of bottom-up
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merge sort appeared in a report by Goldstine and von Neumann as early as 1948.
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.PARAMETER numIntegers
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Specifies the number of integers to sort
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.EXAMPLE
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PS> ./measure-MergeSort.ps1
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🧭 0.378 sec to sorting 1000 integers by MergeSort
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.LINK
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https://github.com/fleschutz/PowerShell
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.NOTES
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Author: Markus Fleschutz | License: CC0
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#>
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param([int]$numIntegers = 1000)
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class MergeSort {
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static Merge($theArray, $tempArray, $leftPos, $rightPos, $rightEnd) {
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$leftEnd = $rightPos - 1
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$tmpPos = $leftPos
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$numElements = $rightEnd - $leftPos + 1
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while (($leftPos -le $leftEnd) -and ($rightPos -le $rightEnd)) {
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if ($theArray[$leftPos].CompareTo($theArray[$rightPos]) -le 0) {
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$tempArray[$tmpPos++] = $theArray[$leftPos++]
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}
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else {
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$tempArray[$tmpPos++] = $theArray[$rightPos++]
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}
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}
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while ($leftPos -le $leftEnd) { $tempArray[$tmpPos++] = $theArray[$leftPos++] }
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while ($rightPos -le $rightEnd) { $tempArray[$tmpPos++] = $theArray[$rightPos++] }
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for ($i = 0; $i -lt $numElements; $i++, $rightEnd--) {
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$theArray[$rightEnd] = $tempArray[$rightEnd]
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}
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}
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static Sort($theArray) {
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$tempArray = New-Object Object[] $theArray.Count
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[MergeSort]::Sort($theArray, $tempArray, 0, ($theArray.Count - 1))
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}
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static Sort($theArray, $tempArray, $left, $right) {
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if ($left -lt $right) {
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$center = [Math]::Floor(($left + $right) / 2)
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[MergeSort]::Sort($theArray, $tempArray, $left, $center)
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[MergeSort]::Sort($theArray, $tempArray, ($center + 1), $right)
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[MergeSort]::Merge($theArray, $tempArray, $left, ($center + 1), $right)
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}
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}
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}
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$list = (1..$numIntegers | foreach{Get-Random -minimum 1 -maximum $numIntegers})
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$stopWatch = [system.diagnostics.stopwatch]::startNew()
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[MergeSort]::Sort($list)
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[float]$elapsed = $stopWatch.Elapsed.TotalSeconds
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$elapsed3 = "{0:N3}" -f $elapsed # formatted to 3 decimal places
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"🧭 $elapsed3 sec to sort $numIntegers integers by MergeSort"
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exit 0 # success
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```
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*(generated by convert-ps2md.ps1 using the comment-based help of measure-MergeSort.ps1 as of 09/20/2023 17:04:42)*
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