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Ublas : |
From: Dominik Szczerba (dominik_at_[hidden])
Date: 2008-09-01 16:28:24
On Monday 01 September 2008 10:22:01 pm Gunter Winkler wrote:
> Dominik Szczerba schrieb:
> > is it also available for small dense matrices?
>
> no - only sparse types can use a different index base. Why is such a
> feature important for dense matrices?
for the same reason as base index: notation compatibility (matlab, fortran)
> A workaround is to create a custom matrix class like
>
> // untested
> class my_matrix : public matrix<double> {
> ...
> const double & operator() (size_type i, size_type j) const {
> return matrix<double>::operator()(i-1, j-1);
> }
this will have quite some overhead for frequent calls, will it not?
>
> >>> - unfold a matrix into vector, like in matlab v=m(:)
> >>
> >> It's possible, though not 'officially' supported.
> >
> > any hint how? just referencing the first element of the matrix?
>
> Yes. You can always use &(v.data()[0]) to get a raw pointer to the data.
can I 'mount' or 'wrap' this pointer in a vector?
thanks a lot,
Dominik
>
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-- Dominik Szczerba, Ph.D. Computational Physics Group Foundation for Research on Information Technologies in Society http://www.itis.ethz.ch