Re: Ublas library

From: Alexey Nikitin (yg-boost-users_at_[hidden])
Date: 2003-06-24 03:57:26

Hi Joerg,

you wrote:

> Interesting problem: the naive solution
>
> ----------
> #include <boost/numeric/ublas/matrix.hpp>
>
> using namespace boost::numeric::ublas;
>
> template<class Matrix>
>  void ProcessRecursive(Matrix& m)
>  {
>    typedef matrix_range<Matrix> MatrixRange;
>    MatrixRange mr = project(m, range(0,m.size1()/2),
range(0,m.size2()/2));
>    if (mr.size1() > 0 && mr.size2() > 0)
>      ProcessRecursive(mr);
>  }
>
> void StartProcess()
>  {
>    matrix<double> m;
>    ProcessRecursive(m);
>  }
>
> int main()
>  {
>     StartProcess();
>  }
>
> ----------
>
> doesn't terminate to compile ;-)
>

I'll try to write the code like I want to see:

----------
#include <boost/numeric/ublas/matrix.hpp>

 using namespace boost::numeric::ublas;

 template<class Matrix>
void ProcessRecursive(Matrix& m)
{
  typedef matrix_range<typename Matrix::matrix_type> MatrixRange;
  // this compile only for Matrix == matrix_range,
  // because for matrix matrix_type is not defined (why not?)

  MatrixRange mr = project(m, range(0,m.size1()/2), range(0,m.size2()/2));
  // here compiler always selects non-specialized version of project,
  // because m is non-constant reference.

  if (mr.size1() > 0 && mr.size2() > 0)
    ProcessRecursive(mr);
}

 void StartProcess()
{
  matrix<double> m(10, 10); // ;)
  ProcessRecursive(m);
}

 int main()
{
  StartProcess();
}

 ----------
>
> Which compiler are you using?
>

VC++ 7.1

> > Do somebody help my to write this code correctly? Or fix library?
>
> How?
>

1. Add "typedef self_type matrix_type;" in definition of class matrix
2. Add
    template<class M>
    BOOST_UBLAS_INLINE
    matrix_range<M> project (matrix_range<M> &data, const range &r1, const
range &r2) {
        return data.project (r1, r2);
    }
    in matix_proxy.hpp (ver. 1.12) on line 3585. It may be need to add the
same code for other proxy types .

After those changes my code shown above compiles correctly and even runs. ;)

Thanks,
Alexey.