VBA: faster way to compare two ranges? - excel

Question

I need to compare two ranges and see if value in one range appears in the other. This is the code I use:
Dim rng1 As Range
Dim rng2 As Range
Dim cell as Range
Dim found as Range
set rng1 = ....
set rng2 = ....
for each cell in rng1
set found = rng2.Find(what:=cell,.....
Next cell
This code is OK if the range is in thousands of rows, single column. When it comes to tens of thousands, it's very slow.
Anyway to speed it up?

Answer 1

This might be the fastest way for large amounts of data:
Option Explicit
Sub Test()
Dim rng1 As Range
Set rng1 = YourShorterRange
Dim rng2 As Range
Set rng2 = YourLargerRange
Dim C As Range
Dim Matches As Object: Set Matches = CreateObject("Scripting.Dictionary")
'input the larger data inside a dictionary
For Each C In rng2
If Not Matches.Exists(C.Value) Then Matches.Add C.Value, 1
Next C
Dim i As Long
Dim arr As Variant
'input the shorter data inside an array
arr = rng1.Value
For i = 1 To UBound(arr)
If Matches.Exists(arr(i, 1)) Then
'your code if the value is found
End If
Next i
End Sub
Edit for Dorian:
Option Explicit
Sub Test()
Dim rng1 As Range
Set rng1 = YourShorterRange
Dim rng2 As Range
Set rng2 = YourLargerRange
Dim i As Long, j As Long
Dim arr As Variant
Dim Matches As Object: Set Matches = CreateObject("Scripting.Dictionary")
arr = rng1.Value
'input the larger data inside a dictionary
For i = 1 To UBound(arr)
For j = 1 To UBound(arr, 2)
If Not Matches.Exists(arr(i, j)) Then Matches.Add arr(i, j), 1
Next j
Next i
'input the shorter data inside an array
arr = rng2.Value
For i = 1 To UBound(arr)
For j = 1 To UBound(arr, 2)
If Matches.Exists(arr(i, j)) Then
'your code if the value is found
End If
Next j
Next i
End Sub

Answer 2

Maybe something along these lines:
Sub Test()
Dim arr1 As Variant, arr2 As Variant
Dim arrList As Object: Set arrList = CreateObject("System.Collections.ArrayList")
Dim x As Long
arr1 = rng1 'Specify your range
arr2 = rng2 'Specify your range
For x = LBound(arr2) To UBound(arr2)
arrList.Add arr2(x, 1)
Next x
For x = LBound(arr1) To UBound(arr1)
If arrList.contains(arr1(x, 1)) = True Then
Debug.Print arr1(x, 1) & " contained within range 2"
End If
Next x
End Sub

Answer 3

I would suggest you :
Application.match
You can also look here you will find an interesting studies on 3 different ways of Search. Those 3 Different way will be studied By Time and By number of occurences.
According Fastexcel the conclusion of this study is :
Don’t use Range.Find unless you want to search a large number of
columns for the same thing (you would have to do a Match for each
column).
The Variant array approach is surprisingly effective,
particularly when you expect a large number of hits.
Match wins easily
for a small number of hits.
So If you except a large number of hit you might have to give a try variant array method. The 3 ways are listed in Fastexcel tuto
Edit
After reading some comment I did a new test :
Variant code
Sub Test1()
Dim vArr As Variant
Dim j As Long
Dim n As Long
Dim dTime As Double
dTime = MicroTimer
vArr = Range("A1:B100000").Value2
Dim Matches As Object: Set Matches = CreateObject("Scripting.Dictionary")
arr = Range("G1:G15").Value
For i = 1 To UBound(arr)
For j = 1 To UBound(arr, 2)
If Not Matches.Exists(arr(i, j)) Then Matches.Add arr(i, j), 1
Next j
Next i
For j = LBound(vArr) To UBound(vArr)
If Matches.Exists(vArr(j, 1)) Or Matches.Exists(vArr(j, 2)) Then n = n + 1
Next j
Debug.Print "Using Variant : " & n & " Timer :" & (MicroTimer - dTime) * 1000
End Sub
Dictionary
Sub Test()
Dim rng1 As Range
Set rng1 = Range("A1:B100000")
Dim rng2 As Range
Set rng2 = Range("G1:G15")
Dim i As Long, j As Long
Dim arr As Variant
Dim dTime As Double
dTime = MicroTimer
Dim Matches As Object: Set Matches = CreateObject("Scripting.Dictionary")
arr = rng2.Value
'input the larger data inside a dictionary
For i = 1 To UBound(arr)
For j = 1 To UBound(arr, 2)
If Not Matches.Exists(arr(i, j)) Then Matches.Add arr(i, j), 1
Next j
Next i
'input the shorter data inside an array
arr = rng1.Value
For i = 1 To UBound(arr)
For j = 1 To UBound(arr, 2)
If Matches.Exists(arr(i, j)) Then
'your code if the value is found
cpt = cpt + 1
End If
Next j
Next i
Debug.Print "Using Damian Method : " & cpt & " Timer : " & (MicroTimer - dTime) * 1000
End Sub