5x5 matrix inverse

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5x5 matrix inverse

Hi friends,

I want to ask a question about finding matrix which is type 5x5 inversion. These my code. This was formed by gauss jordan elimination method.

I get overflow error in this line "Dizi(i, j) = Dizi(i, j) / y".

vb Code:

'the variants were defined and assigned
 
For i = 1 To 5
    Dizi(i, i + 5) = 1
Next
 
For i = 1 To 4
For j = i + 1 To 5
    If Dizi(i, i) = 0 Then
        For k = i + 1 To 5
        If Dizi(k, i) <> 0 Then
            For l = 1 To 10
                Dizi(i, l) = Dizi(i, l) + Dizi(k, l)
            Next l
        End If
        Next k
    End If
    
    w = Dizi(j, i) / Dizi(i, i)
    For l = 1 To 10
        Dizi(j, l) = Dizi(j, l) - w * Dizi(i, l)
    Next l
Next j
Next i
 
 
    For i = 5 To 2 Step -1
    For j = 4 To 1 Step -1
        If Dizi(i, i) = 0 Then
            For k = i - 1 To 1 Step -1
                If Dizi(k, i) <> 0 Then
                    For l = 1 To 10
                        Dizi(i, l) = Dizi(i, l) + Dizi(k, l)
                    Next l
                End If
            Next k
        End If
        
    w = Dizi(j, i) / Dizi(i, i)
        For l = 1 To 10
            Dizi(j, l) = Dizi(j, l) - w * Dizi(i, l)
        Next l
    Next j
    Next i
    
    For i = 1 To 5
        If Dizi(i, i) <> 1 Then y = Dizi(i, i)
    For j = 1 To 10
        Dizi(i, j) = Dizi(i, j) / y
    Next j
    Next i

Could you say where the mistake is?

Mar 10th, 2012, 04:05 PM
Milk

Re: 5x5 matrix inverse

This might be more suited in the Visual Basic 6 and Earlier forum.

What is the value of Y on that line? 0?

'the variants were defined and assigned

Is Y one of those variants? Can you show this bit? Using doubles might be more appropriate for what you are doing.
Mar 10th, 2012, 09:37 PM
jemidiah

Re: 5x5 matrix inverse

Your implementation seems very buggy (I tried it with the identity matrix and it broke immediately after zeroing out the 4th and 9th columns for no apparent reason). Rather than writing your own code and debugging it, you should just google "VB6 matrix inverse". This problem has certainly been solved many times; it's not worth anyone's time to solve it again in this case.