# Mark a matrix "upper" in a oct-file

4 messages
Open this post in threaded view
|

## Mark a matrix "upper" in a oct-file

 Dear all, I have to take the upper triangular part of a matrix in a oct-file. Later, I have to perform RowVector-Matrix products with it. This is my code // given Matrix F(m,m) // take the upper triangular part for (octave_idx_type j = 0; j < m; j++)      {        for (octave_idx_type i = j+1; i < m; i++)   F(i,j) = 0.0;      }    RowVector d = F.row(0); // make RowVector-matrix products    for (octave_idx_type i = 0; i < s-1; i++)      d = d * F; My question is: if I mark the matrix "upper" (but do not know how to do it), is the RowVector-Matrix product faster (for instance BLAS dtrmv is used instead of general dgemv)? Thanks, Marco _______________________________________________ Help-octave mailing list [hidden email] https://lists.gnu.org/mailman/listinfo/help-octave
Open this post in threaded view
|

## Re: Mark a matrix "upper" in a oct-file

 > Le 5 sept. 2014 à 13:56, Marco Caliari <[hidden email]> a écrit : > > Dear all, > > I have to take the upper triangular part of a matrix in a oct-file. Later, I have to perform RowVector-Matrix products with it. This is my code > > // given Matrix F(m,m) > // take the upper triangular part > for (octave_idx_type j = 0; j < m; j++) >    { >      for (octave_idx_type i = j+1; i < m; i++) >    F(i,j) = 0.0; >    } >  RowVector d = F.row(0); > // make RowVector-matrix products >  for (octave_idx_type i = 0; i < s-1; i++) >    d = d * F; > > My question is: if I mark the matrix "upper" (but do not know how to do it), is the RowVector-Matrix product faster (for instance BLAS dtrmv is used instead of general dgemv)? > Look at the matrix_type function for how to mark the matrix as upper. However, marking it as such is only useful at this point for the solve function or slash operators. D. > Thanks, > > Marco > > _______________________________________________ > Help-octave mailing list > [hidden email] > https://lists.gnu.org/mailman/listinfo/help-octave_______________________________________________ Help-octave mailing list [hidden email] https://lists.gnu.org/mailman/listinfo/help-octave