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excel – Best workaround for VBA Transpose array length limit?

Posted by: admin March 9, 2020 Leave a comment

Questions:

After running a simulation with 100,000 iterations, I tried to dump the values from each iteration into a column. Here is the gist of the code:

Sub test()
Application.ScreenUpdating = False
Dim totalgoals() As Variant, ko As Worksheet, out As Worksheet, iter As Long
Set ko = Sheets("KO Sim")
Set out = Sheets("Monte Carlo")
iter = out.Range("P2").Value
For i = 1 To iter
    ko.Calculate
    If i = 1 Then
        ReDim totalgoals(1 To 1, 1 To 1) As Variant
        totalgoals(1, 1) = ko.Range("F23").Value
    Else
        ReDim Preserve totalgoals(1 To 1, 1 To i) As Variant
        totalgoals(1, i) = ko.Range("F23").Value
    End If
Next i
out.Range("U1:U" & iter) = Application.WorksheetFunction.Transpose(totalgoals)
Application.ScreenUpdating = True
End Sub

This throws a Type Mismatch error on the next to last line because Transpose can only handle arrays of length up to 2^16 (~64,000). So, how should I workaround this? What is my most efficient option?

I set up my code to store the values in an array just for the easy output, but it seems that’s not going to work for this many values. Would I be better off sticking with arrays and just write my own transpose function (i.e., loop through the array and write the values to a new array), or would I be better off working with a different class from the start, like a collection, if I’m just going to have to loop through the results in the end anyway?

Or better yet, is there anyway to do this without having to loop through the values again?

EDIT:

I provided a bad example because the ReDim Preserve calls were unnecessary. So, consider the following instead where they are necessary.

ReDim totalgoals(1 To 1, 1 To 1) As Variant
For i = 1 To iter
    ko.Calculate
    If ko.Range("F23") > 100 Then
        If totalgoals(1, 1) = Empty Then
            totalgoals(1, 1) = ko.Range("F23").Value
        Else
            ReDim Preserve totalgoals(1 To 1, 1 To UBound(totalgoals, 2) + 1) As Variant
            totalgoals(1, UBound(totalgoals, 2)) = ko.Range("F23").Value
        End If
    End If
Next i
out.Range("U1").Resize(UBound(totalgoals, 2),1) = Application.WorksheetFunction.Transpose(totalgoals)
How to&Answers:

Here’s a version of your code that should work and be faster:

Sub test()
Application.ScreenUpdating = False
Dim totalgoals() As Variant, ko As Worksheet, out As Worksheet, iter As Long
Set ko = Sheets("KO Sim")
Set out = Sheets("Monte Carlo")
iter = out.Range("P2").Value

' ReDim it completely first, already transposed:
ReDim totalgoals(1 To iter, 1 To 1) As Variant

For i = 1 To iter
    ko.Calculate
    totalgoals(i, 1) = ko.Range("F23").Value
Next i
out.Range("U1:U" & iter) = totalgoals
Application.ScreenUpdating = True
End Sub

Here’s a version that keeps the conditional ReDims, but manually transposes the array at the end:

Sub test()
Application.ScreenUpdating = False
Dim totalgoals() As Variant, ko As Worksheet, out As Worksheet, iter As Long
Set ko = Sheets("KO Sim")
Set out = Sheets("Monte Carlo")
iter = out.Range("P2").Value
For i = 1 To iter
    ko.Calculate
    If i = 1 Then
        ReDim totalgoals(1 To 1, 1 To 1) As Variant
        totalgoals(1, 1) = ko.Range("F23").Value
    Else
        ReDim Preserve totalgoals(1 To 1, 1 To i) As Variant
        totalgoals(1, i) = ko.Range("F23").Value
    End If
Next i
' manually transpose it
Dim trans() As Variant
ReDim trans(1 to UBound(totalgoals), 1 to 1)
For i = 1 to UBound(totalgoals)
    trans(i, 1) = totalgoals(1, i)
Next i
out.Range("U1:U" & iter) = trans
Application.ScreenUpdating = True
End Sub

Answer:

Calculation is definitely going to be the bottleneck here, so (as RBarryYoung says) transposing the array entry-by-entry won’t really affect the speed at which your macro runs.

That said, there is a way to transpose a 2D row to a column (and vice versa) in constant time:

Private Declare Function VarPtrArray Lib "msvbvm60" Alias _
    "VarPtr" (ByRef Var() As Any) As Long
Private Declare Sub GetMem4 Lib "msvbvm60.dll" (src As Any, dest As Any)
Private Declare Sub GetMem8 Lib "msvbvm60.dll" (src As Any, dest As Any)

Sub test()
    Dim totalgoals() As Single
    Dim f As Single
    Dim i As Long, iter As Long

    'dimension totalgoals() with as many cells as we
    'could possibly need, then cut out the excess
    iter = 100000
    ReDim totalgoals(1 To 1, 1 To iter)
    For iter = iter To 1 Step -1
        f = Rnd
        If f > 0.2 Then
            i = i + 1
            totalgoals(1, i) = f
        End If
    Next iter
    ReDim Preserve totalgoals(1 To 1, 1 To i)

    'transpose by swapping array bounds in memory
    Dim u As Currency
    GetMem8 ByVal VarPtrArray(totalgoals) + 16, u
    GetMem8 ByVal VarPtrArray(totalgoals) + 24, _
            ByVal VarPtrArray(totalgoals) + 16
    GetMem8 u, ByVal VarPtrArray(totalgoals) + 24
End Sub