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

**From**: |
David Bateman |

**Subject**: |
Re: Mark a matrix "upper" in a oct-file |

**Date**: |
Fri, 5 Sep 2014 16:27:34 +0200 |

>* Le 5 sept. 2014 à 13:56, Marco Caliari <address@hidden> 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*
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>* https://lists.gnu.org/mailman/listinfo/help-octave*