Fibonacci sequence generator overflow

[Exceladd1ct]

Hello,

I wrote a piece of code that would generate fibonacci sequence, but there is no data type that can hold such big numbers, is there a workaround to make the code contiune to do the math with big numbers?

Thanks.

Option Explicit

Sub Fibonacci()
    Dim i As LongPtr, k As LongPtr
    i = 0
    k = 1
    
    Debug.Print i
    Debug.Print k
    
    Dim x As LongPtr, q As LongPtr, j As LongPtr, a As Long
    
    x = i + k 'x = 0+1
    q = x + k 'q = 1+1
    j = x + q 'j = 1+2
    
    Debug.Print k
    Debug.Print j
        For a = 1 To 1000
        x = q
        q = j
        j = x + q
        Debug.Print j
    Next
    
End Sub

 

[Rick Rothstein]

Here is a function that will generate the Nth Fibonacci number where N has no practical limit... the limitation is on the outputted number which cannot be more than 2,147,483,647 digits long (the maximum length of a text string).

Function Fibonacci(ByVal N As Long) As String
  Dim f(1 To 3, 1 To 32767) As Byte
  Dim i As Long, loc As Long
  Dim addIx1 As Byte, addIx2 As Byte, sumIx As Byte
  Dim Carry As Byte, MaxLen As Long, nextDigit As Byte
  f(1, 1) = 1
  f(2, 1) = 1
  addIx1 = 1
  addIx2 = 2
  sumIx = 3
  MaxLen = 1
  For i = 3 To N
    Carry = 0
    loc = 1
    Do
      nextDigit = f(addIx1, loc) + f(addIx2, loc) + Carry
      If loc > MaxLen And nextDigit = 0 Then Exit Do
      f(sumIx, loc) = nextDigit Mod 10
      Carry = nextDigit \ 10
      loc = loc + 1
    Loop
    MaxLen = loc - 1
    addIx1 = (addIx1 Mod 3) + 1
    addIx2 = (addIx2 Mod 3) + 1
    sumIx = (sumIx Mod 3) + 1
  Next i
  For i = 1 To MaxLen
      Fibonacci = f(addIx2, i) & Fibonacci
  Next i
End Function

To use it the way you want, simply create a subroutine that will iterate from 1 to what ever Fibonacci number you want. For example, this one which will list the first 100 Fibonacci numbers to the Immediate Window...

Sub ListFibonacciNumbers()
  Dim N As Long
  For N = 1 To 100
    Debug.Print "Fibonacci(" & N & ") = " & Fibonacci(N)
  Next
End Sub

Note: The Fibonacci function above was written by Eric W and uses Byte arrays to speed up a function I posted awhile ago which used much slower text string manipulations.

 

[Rick Rothstein]

@Exceladd1ct... are you still following this thread you started? I am wondering if the code I posted works for you or not.

 

[Exceladd1ct]

@Exceladd1ct... are you still following this thread you started? I am wondering if the code I posted works for you or not.

Hello Rick,

Sorry for the late reply. Your Code is exactly what i was looking for.
Thank you for your support.