[vtkusers] LUFactorLinearSystem - How to get L and U?

[David Gobbi]

Most likely, if

A* =
[a b]
[c d]

then

L =
[1 0]
[c 1]

U =
[a b]
[0 d]

However, I'll have to leave it up to you to prove that this is
actually the case for the algorithm that VTK uses.

 - David



On Tue, Jun 25, 2013 at 2:38 PM, David Doria <daviddoria at gmail.com> wrote:
> Here is a little example that tries to factor the matrix
> [4 3]
> [6 3]
>
> http://www.vtk.org/Wiki/VTK/Examples/Broken/LUFactorization
>
> The documentation says "Output factorization LU is in matrix A" (it is
> written over the matrix that is passed in). I don't understand this
> though - the matrix is 2x2, and there are 3 non-zero entries of each
> of L and U (for a total of 6). Can anyone explain how to get L and U?
>
> Thanks,
>
> David