[Gambas-user] Improve a Fast routine

[Jussi Lahtinen]

What are you trying to do exactly? Have you looked up ready well known
algorithm for it?
By quick look that seems to be O(n^3), which makes me think it can done
faster.


Jussi

On Fri, Nov 28, 2014 at 2:02 AM, martin p cristia <tercoide at ...67...>
wrote:

> Hi, is there any way to speed up this routine?
> Thanks
>
> Fast Public Function solucionarXgauss(x As Float[], ti As Float[],
> iOrden As Integer) As Integer
>      ' OK GAMBAS
>
>      Dim c1 As Float
>      Dim i As Integer, j As Integer, a As Integer, b As Integer, ok As
> Integer
>      Dim l As Integer, h As Integer, i1 As Integer, j1 As Integer
>      Dim p1 As Float, iTest As Integer, nTest As Integer
>
>      contador = 0
>      If iOrden = 0 Then Return 0
>      ok = True
>
>      'usa el metodo de Gauss
>      'debe ser cuadrada la matriz
>      ' triangulacion
>      itest = iorden / 100
>
>      For i = 0 To iOrden - 1
>
>
>          'This is to show the progress in the GUI
>          FMain.debugInfo("Resolviendo el sistema ", True, Format$(100 *
> i / iorden, "0.00") & "%")
>
>          If debanda(i, i) <> 0 Then
>              For j = i + 1 To iOrden - 1
>                  If debanda(j, i) <> 0 Then
>                      c1 = - debanda(j, i) / debanda(i, i)
>                      For h = i To iOrden - 1
>                          addbanda(j, h, c1 * debanda(i, h))
>
>                      Next
>                      ti[j] = ti[j] + c1 * ti[i]
>                  End If
>              Next
>          Else
>              Return
>              l = i
>              If i = iOrden - 1 Or l > iOrden - 1 Then Return 0 ' el
> sistema es incompatible
>
>              Do
>                  If debanda(l, i) <> 0 Then
>                      For h = 0 To iOrden - 1
>                          addbanda(i, h, debanda(l, h))
>                      Next
>                      ti[i] = ti[i] + ti[l]
>                      Exit
>                  Else
>                      l = l + 1
>                      If i = iOrden - 1 Or l > iOrden - 1 Then Return 0 '
> el sistema es incompatible
>                  End If
>              Loop
>          End If
>
>      Next
>      ' sustitucion atrás
>
>      x[iOrden - 1] = ti[iOrden - 1] / debanda(iOrden - 1, iOrden - 1)
>      For i = iOrden - 2 To 0 Step -1
>          p1 = 0
>          For j = i + 1 To iOrden - 1
>              p1 = p1 - x[j] * debanda(i, j)
>
>          Next
>          p1 = ti[i] + p1
>          x[i] = p1 / debanda(i, i)
>      Next
>      Return ok
>
> End Function
>
> Fast Public Sub ABanda(ib As Integer, jb As Integer, valor As Float)
>
>
>      modCalculus.MatRigEst[ib * modEstru.ordmatrig + jb] = valor
>
>   Return
>
>
> End Sub
>
> DeBanda() and AddBanda() are similar
>
>
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