Optimize this VBA lookup loop in Excel - arrays

Question

I want to optimize the following code, as it is very slow.
I am using the code found in this answer:
https://stackoverflow.com/a/27108055/1042624
However, it is very slow when looping through +10k rows. Is it possible to optimize my code below? I have tried to modify it a bit, but it does not seem to work.
Sub DeleteCopy2()
Dim LastRow As Long
Dim CurRow As Long
Dim DestLast As Long
Dim strSheetName As String
Dim arrVal() As Long
Application.ScreenUpdating = False
Application.Calculation = xlManual
strSheetName = "Week " & ISOWeekNum(Format(Date)) - 1
LastRow = Sheets("MatchData").Range("A" & Rows.Count).End(xlUp).Row
DestLast = Sheets(strSheetName).Range("A" & Rows.Count).End(xlUp).Row
ReDim arrVal(2 To LastRow) ' Headers in row 1
For CurRow = LBound(arrVal) To UBound(arrVal)
If Not Sheets(strSheetName).Range("A2:A" & DestLast).Find(Sheets("MatchData").Range("A" & CurRow).Value, LookIn:=xlValues, LookAt:=xlWhole) Is Nothing Then
Sheets("MatchData").Range("A" & CurRow).Value = ""
Else
End If
Next CurRow
Application.ScreenUpdating = True
Application.Calculation = xlCalculationAutomatic
End Sub

Answer 1

Can you try this for me? I have commented the code so that you will not have a problem understanding it. Also check how much time it takes for 10k+ rows
Logic
Store search values in array 1
Store destination values in array 2
Loop through the first array and check if it is present in the second array. If present, clear it
Clear the search values from sheet1
Output the array to the sheet1
Sort Col A so that the blanks go down.
Code
Sub Sample()
Dim wbMatch As Worksheet, wbDestSheet As Worksheet
Dim lRow As Long, i As Long
Dim MArr As Variant, DArr As Variant
Dim strSheetName As String
Dim rng As Range
strSheetName = "Sheet2" '"Week " & IsoWeekNum(Format(Date)) - 1
'~~> Set your worksheets
Set wbMatch = Sheets("MatchData")
Set wbDestSheet = Sheets(strSheetName)
'~~> Store search values in 1st array
With wbMatch
lRow = .Range("A" & .Rows.Count).End(xlUp).Row
Set rng = .Range("A2:A" & lRow)
MArr = rng.Value
End With
'~~> Store destination values in the 2nd array
With wbDestSheet
lRow = .Range("A" & .Rows.Count).End(xlUp).Row
DArr = .Range("A2:A" & lRow).Value
End With
'~~> Check if the values are in the other array
For i = LBound(MArr) To UBound(MArr)
If IsInArray(MArr(i, 1), DArr) Then MArr(i, 1) = ""
Next i
With wbMatch
'~~> Clear the range for new output
rng.ClearContents
'~~> Output the array to the worksheet
.Range("A2").Resize(UBound(MArr), 1).Value = MArr
'~~> Sort it so that the blanks go down
.Columns(1).Sort Key1:=.Range("A2"), Order1:=xlAscending, Header:=xlYes, OrderCustom:=1, _
MatchCase:=False, Orientation:=xlTopToBottom, DataOption1:=xlSortNormal
End With
End Sub
'~~> function to check is a value is in another array
Function IsInArray(stringToBeFound As Variant, arr As Variant) As Boolean
Dim j As Long
For j = 1 To UBound(arr, 1)
On Error Resume Next
IsInArray = Application.Match(stringToBeFound, Application.Index(arr, , i), 0)
On Error GoTo 0
If IsInArray = True Then Exit For
Next
End Function
Edit
Another way. Based on the sample file, this code runs in approx 1 minute.
Start : 8/4/2016 08:59:36 PM
End : 8/4/2016 09:00:47 PM
Logic:
It uses CountIf to check for duplicates and then deletes the duplicates using .Autofilter
Sub Sample()
Dim wbMatch As Worksheet, wbDestSheet As Worksheet
Dim lRow As Long
Dim strSheetName As String
Dim rng As Range
Debug.Print "Start : " & Now
strSheetName = "Week " & ISOWeekNum(Format(Date)) - 1
'~~> Set your worksheets
Set wbMatch = Sheets("MatchData")
Set wbDestSheet = Sheets(strSheetName)
'~~> Store search values in 1st array
With wbMatch
lRow = .Range("A" & .Rows.Count).End(xlUp).Row
.Columns(2).Insert
Set rng = .Range("B2:B" & lRow)
lRow = wbDestSheet.Range("A" & wbDestSheet.Rows.Count).End(xlUp).Row
rng.Formula = "=COUNTIF('" & strSheetName & "'!$A$1:$A$" & lRow & ",A2)"
DoEvents
rng.Value = rng.Value
.Range("B1").Value = "Temp"
'Remove any filters
.AutoFilterMode = False
With .Range("A1:E" & lRow) 'Filter, offset(to exclude headers) and delete visible rows
.AutoFilter Field:=2, Criteria1:=">0"
.Offset(1, 0).SpecialCells(xlCellTypeVisible).EntireRow.Delete
End With
'Remove any filters
.AutoFilterMode = False
.Columns(2).Delete
End With
Debug.Print "End : " & Now
End Sub

Answer 2

Looks like #SiddarthRout and I were working in parallel...
My code example below executes in less than 2 secs (eyeball estimate) over almost 12,000 rows.
Option Explicit
Sub DeleteCopy2()
Dim codeTimer As CTimer
Set codeTimer = New CTimer
codeTimer.StartCounter
Dim thisWB As Workbook
Dim destSH As Worksheet
Dim matchSH As Worksheet
Set thisWB = ThisWorkbook
Set destSH = thisWB.Sheets("Week 32")
Set matchSH = thisWB.Sheets("MatchData")
Dim lastMatchRow As Long
Dim lastDestRow As Long
lastMatchRow = matchSH.Range("A" & matchSH.Rows.Count).End(xlUp).Row
lastDestRow = destSH.Range("A" & matchSH.Rows.Count).End(xlUp).Row
'--- copy working data into memory arrays
Dim destArea As Range
Dim matchData As Variant
Dim destData As Variant
matchData = matchSH.Range("A1").Resize(lastMatchRow, 1)
Set destArea = destSH.Range("A1").Resize(lastDestRow, 1)
destData = destArea
Dim i As Long
For i = 2 To lastDestRow
If Not InMatchingData(matchData, destData(i, 1)) Then
destData(i, 1) = ""
End If
Next i
'--- write the marked up data back to the worksheet
destArea = destData
Debug.Print "Destination rows = " & lastDestRow
Debug.Print "Matching rows = " & lastMatchRow
Debug.Print "Execution time = " & codeTimer.TimeElapsed & " secs"
End Sub
Private Function InMatchingData(ByRef dataArr As Variant, _
ByRef dataVal As Variant) As Boolean
Dim i As Long
InMatchingData = False
For i = LBound(dataArr) To UBound(dataArr)
If dataVal = dataArr(i, 1) Then
InMatchingData = True
Exit For
End If
Next i
End Function
The timing results from my code are (using the timer class from this post ):
Destination rows = 35773
Matching rows = 23848
Execution time = 36128.4913359179 secs