PBWin Slot Sort #2 – twice as fast as PB string sort

[Stanley Durham Member Find all posts View Profile Close Stanley Durham]

On random strings (Asc(32) to Asc(127)); 3 to 50 chars: it is consistently twice as fast.
That only amounts to a split-second on 100,000 strings.

(Asc(32) to Asc(127)); 3 to 2,000 chars: 4 to 5 times faster.

This sort really shines on very long strings.
Long strings reach their final destination quickly.
If you were sorting millions of strings, up to thousands of characters wide, this sort would be worth considering.

Slot Sort:
Works sideways through the strings in an array, at a given character depth.
Now makes 3 passes and uses a temporary array. (two passes in previous version)
Pass 1: get count for each type of character (0 – 255)
Determines where each slot begins: slot 0 … slot 255
Pass 2: copies string pointer into temporary array in proper slot
Pass 3: copies string pointers back into original array
It’s actually faster to use a temporary array, and extra pass, than swapping pointers in place. No decision loops.
All strings in slot zero have reached their final destination. Null on end of string.
All slots containing only one string have reached their final destination. (that’s why the sort shines on really long string)
Recursively sort all remaining slots on next character down.

The sort only works down far enough to find a set of matching strings, or a single unique string.

Note: this is just a test of concept. This version doesn’t test for null strings in the array to be sorted. A null string will cause a crash. Arr(i) = “”

#PBForms CREATED V1.51
'pbwin 9
$TestSource = "SlotSort.bas"
$TestTitle = "Slot Sort Test"
#Compile Exe "SlotSort.exe"
#Dim All
#Optimize Speed
    'Slot Sort - new sort algorithm
    '   constantly about twice as fast as PB array sort
    '   (about 50% to 75% faster on "A" ~ "z"; 65 to 122)
    '   mix of short and really long strings: 4 to 5 times faster (random strings 3 to 2,000 chars)
    '
    '   Note: this is not suggested as an alternative to PB sort
    '       only posted to test the concept
    '
    '   this is a recursive radix type sort
    '
    '   - now makes three passes
    '   - uses two temporary arrays
    '
    '   Passes:
    '       1. get count for each different kind of character, at a given depth, for each string in array
    '           1a. build slot information - where each string belong in array
    '       2. goes through array and stores each string ptr in temp array in proper slot
    '       3. copies string pointers back into original array
    '               now in sorted order for current depth
    '           3a. recursively sort each slot
    '               skip slot zero (end-of-string) now in final position
    '               skip slots with only one string - in final position
    '
    '   currently, doesn't test for null strings in test array: arr(i) = ""
 
#PBForms BEGIN INCLUDES
#If Not %Def(%WINAPI)
    #Include Once "WIN32API.INC"
#EndIf
#Include Once "PBForms.INC"
#PBForms END INCLUDES
#PBForms BEGIN CONSTANTS
%Dlg1    =  101
%BtnTest = 1002
%Lbx1    = 1001
#PBForms END CONSTANTS
Declare CallBack Function ShowDlg1Proc()
Declare Function ShowDlg1(ByVal hParent As Dword) As Long
#PBForms DECLARATIONS
Global lbx As LBxI
Global tmr As TimerI
Function PBMain()
    ShowDlg1 %HWND_Desktop
End Function
Type SlotSortT
    slotCount(255) As Long
    slotStart(254) As Long
    slotEnd(255) As Long
End Type
Sub SlotSort(arr() As String)
    Local pArr, pArr2 As Long Ptr
    Local dummy(), charIndex() As Long
    Local lb, ub, Count, depth As Long
    lb = LBound(arr)
    ub = UBound(arr)
    Count = ub - lb + 1
    If Count > 1 Then
        pArr = VarPtr(arr(lb))
        '
        ReDim dummy(lb To ub)
        pArr2 = VarPtr(dummy(lb))
        ReDim charIndex(Count - 1)
        '
        depth = 0
        SlotSortR pArr, pArr2, charIndex(), depth, 0, Count - 1
        '
    End If
End Sub
Sub SlotSortR(ByVal pArr As Long Ptr, ByVal pArr2 As Long Ptr, charIndex() As Long, ByVal depth As Long, ByVal leftSide As Long, ByVal rightSide As Long)
    Register i As Long
    Register char As Long
    Local lastSlotStart, lastSlotCount As Long
    Local ss As SlotSortT
    'Pass #1: get slot counts
    For i = rightSide To leftSide Step -1
        'Incr ss.slotCount(Peek(Byte, @pArr[i] + depth))
        charIndex(i) = Peek(Byte, @pArr[i] + depth)
        Incr ss.slotCount(charIndex(i))
    Next i
    'build slot info
    lastSlotStart = leftSide
    lastSlotCount = 0
    For char = 0 To 255
        If ss.slotCount(char) Then
            ss.slotStart(char) = lastSlotStart + lastSlotCount
            ss.slotEnd(char) = ss.slotStart(char) - 1
            lastSlotStart = ss.slotStart(char)
            lastSlotCount = ss.slotCount(char)
        End If
    Next char
    'Pass #2: store each string in proper slot
    For i = rightSide To leftSide Step -1
        'char = Peek(Byte, @pArr[i] + depth)
        Incr ss.slotEnd(charIndex(i))
        @pArr2[ss.slotEnd(charIndex(i))] = @pArr[i]
    Next i
    'Pass #3: restore slots to original array (string pointers)
    For i = rightSide To leftSide Step -1
        @pArr[i] = @pArr2[i]
    Next i
    'recursively sort each slot on next character down
    '   we skip zero - null on end of string
    '       those strings have reached their final destination
    For char = 255 To 1 Step -1
        'if a slot only has one string - no need to sort - string in final destination
        If ss.slotCount(char) > 1 Then
            SlotSortR pArr, pArr2, charIndex(), depth + 1, ss.slotStart(char), ss.slotEnd(char)
        End If
    Next char
End Sub
 
Sub BtnTest(ByVal hDlg As Long)
    Local i, j As Long
    Local a(), b() As String
    Local s As String
    Local pbTime, ssTime As Double
    Local pbTix, ssTix As Quad
    'test settings
    Local Count As Long          : Count = 100000        'number of random strings to build
    Local shortestString As Long : shortestString = 10   'shortest random string
    Local longestString As Long  : longestString = 50    'longest random string
    Local lowestChar As Long     : lowestChar = 32       'ASC() smallest random character
    Local highestChar As Long    : highestChar = 127     'ASC() largest random character
    'if Count <= 500 then random strings will be displayed
    '   any Count < 100,000 is to small to show any difference
    Randomize
    ReDim a(1 To Count)
    ReDim b(1 To Count)
    lbx.Clear(2)
    lbx.Add("fill arrays")
    For i = 1 To Count
        s = ""
        For j = 1 To Rnd(shortestString, longestString)
            s += Chr$(Rnd(lowestChar, highestChar))
        Next j
        a(i) = s
        b(i) = s
    Next i
    lbx.Add("")
    lbx.Add("PB Sort")
    tmr.Start()
    Tix pbTix
    Array Sort a()
    Tix End pbTix
    tmr.Stop()
    lbx.Add(tmr.Get())
    pbTime = tmr.GetTime
 
    lbx.Add("")
    lbx.Add("Slot Sort")
    tmr.Start()
    Tix ssTix
    SlotSort b()
    Tix End ssTix
    tmr.Stop()
    lbx.Add(tmr.Get())
    ssTime = tmr.GetTime()
    lbx.Add("")
    lbx.Add("see if anything out of order")
    For i = 1 To Count
        If a(i) <> b(i) Then
            ? "out of order at: " + Str$(i)
            Exit For
        End If
    Next i
    lbx.Add("")
    lbx.Add("Tix PB: " + Format$(pbTix))
    lbx.Add("Tix SS: " + Format$(ssTix))
    lbx.Add("TIme PB: " + Format$(pbTime, "####.##########"))
    lbx.Add("Time SS: " + Format$(ssTime, "####.##########"))
    lbx.Add("Slot Sort is " + Format$(pbTime/ssTime) + " times faster than PB sort")
    If Count <= 500 Then
        lbx.Add("")
        lbx.Add("====================")
        For i = 1 To Count
            lbx.Add("")
            lbx.Add("PB: = '" + a(i) +"'")
            lbx.Add("SS: = '" + b(i) +"'")
        Next i
    End If
    lbx.Add("")
    lbx.Add("done...")
End Sub
CallBack Function ShowDlg1Proc()
    Select Case As Long CbMsg
        Case %WM_InitDialog
             lbx = Class "LBxC"
             lbx.INI(Cb.Hndl, %Lbx1)
             lbx.SetHorizontal(1000)
             tmr = Class "TimerC"
        Case %WM_NCActivate
            Static hWndSaveFocus As Dword
            If IsFalse CbWParam Then
                hWndSaveFocus = GetFocus()
            ElseIf hWndSaveFocus Then
                SetFocus(hWndSaveFocus)
                hWndSaveFocus = 0
            End If
        Case %WM_Command
            Select Case As Long CbCtl
                Case %BtnTest
                    If CbCtlMsg = %BN_Clicked Or CbCtlMsg = 1 Then
                        BtnTest(Cb.Hndl)
                    End If
            End Select
    End Select
End Function
Function ShowDlg1(ByVal hParent As Dword) As Long
    Local lRslt  As Long
#PBForms BEGIN DIALOG %Dlg1->->
    Local hDlg   As Dword
    Local hFont1 As Dword
    Dialog New hParent, $TestTitle, 67, 61, 341, 241, %WS_Popup _
        Or %WS_Border Or %WS_DlgFrame Or %WS_Caption Or %WS_SysMenu Or _
        %WS_MinimizeBox Or %WS_ClipSiblings Or %WS_Visible Or %DS_ModalFrame _
        Or %DS_3DLook Or %DS_NoFailCreate Or %DS_SetFont, _
        %WS_Ex_ControlParent Or %WS_Ex_Left Or %WS_Ex_LtrReading Or _
        %WS_Ex_RightScrollbar, To hDlg
    Control Add ListBox, hDlg, %Lbx1, , 5, 5, 330, 210, %WS_Child Or _
        %WS_Visible Or %WS_HScroll Or %WS_VScroll Or %LBS_Notify Or _
        %LBS_NoIntegralHeight, %WS_Ex_ClientEdge Or %WS_Ex_Left Or _
        %WS_Ex_LtrReading Or %WS_Ex_RightScrollbar
    Control Add Button,  hDlg, %BtnTest, "Test", 275, 220, 60, 15
    hFont1 = PBFormsMakeFont("Courier New", 9, 400, %FALSE, %FALSE, %FALSE, _
        %ANSI_CHARSET)
    Control Send hDlg, %Lbx1, %WM_SETFONT, hFont1, 0
#PBForms END DIALOG
    Dialog Show Modal hDlg, Call ShowDlg1Proc To lRslt
#PBForms BEGIN CLEANUP %Dlg1
    DeleteObject hFont1
#PBForms END CLEANUP
    Function = lRslt
End Function
Class LBxC
    Instance meHDlg As Long
    Instance meID As Long
    Interface LBxI
        Inherit IUnknown
        Method INI(ByVal hDlg As Long, ByVal Id As Long)
            meHDlg = hDlg
            meID = Id
        End Method
        Method SetHorizontal(ByVal Count As Long)
            Local hCntrl&
            Control Handle meHDlg, meID To hCntrl&
            SendMessage hCntrl&, %LB_SETHORIZONTALEXTENT, Count, 0
        End Method
        Method Clear(Opt doEventsCount As Long)
            ListBox Reset meHDlg, meID
            If VarPtr(doEventsCount) Then me.DoEventsCount(doEventsCount)
        End Method
        Method Add(ByVal s As String, Opt doEventsCount As Long) As String
            ListBox Add meHDlg, meID, s
            If VarPtr(doEventsCount) Then me.DoEventsCount(doEventsCount)
        End Method
    End Interface
    Class Method DoEventsCount(ByVal Count As Long)
        Local i As Long
        For i = 1 To Count
            Dialog DoEvents
        Next i
    End Method
End Class
Class TimerC
    Instance startTime As Double
    Instance stopTime As Double
    Interface TimerI
        Inherit IUnknown
        Method Start()
            startTime = Timer
        End Method
        Method Stop()
            stopTime = Timer
        End Method
        Method Get() As String
            Method = "    Time: " + Format$(stopTime - startTime, "#####.###############")
        End Method
        Method GetTime() As Double
            Method = stopTime - startTime
        End Method
    End Interface
End Class