[Insight-developers] Numerical methods: an example of places that need improvement.

[brian avants]

right --- or using, for instance, the secret itpack routines that live
inside the FEM library.

On Wed, Nov 3, 2010 at 3:38 PM, Luis Ibanez <luis.ibanez at kitware.com> wrote:
> From our tcon on image registration.
>
>
> The following code:
>
>   vnl_matrix<double> B =
>     vnl_matrix_inverse<double>( N_matrix.transpose() * N_matrix) *
> N_matrix.transpose() * data_matrix;
>
> is from
>
> Insight/Code/Common/
> itkNonUniformBSpline.txx
> (line 313).
> http://public.kitware.com/cgi-bin/viewcvs.cgi/Code/Common/itkNonUniformBSpline.txx?revision=1.9&root=Insight&view=markup
>
>
> It is trying to solve the linear system
>
>              X  = N * B
>
> by doing:
>
>         B = ( N' * N )^-1  *  N'  * X
>
>
> instead of invoking one of the linear solvers
> that we are carrying in ITK via VXL.
>
>
> ----
>
>
>    Luis
>
>



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