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## Re: [Bug-gsl] gsl_blas_dgemv return a 0 vector when using a vector twice

**From**: |
Brian Gough |

**Subject**: |
Re: [Bug-gsl] gsl_blas_dgemv return a 0 vector when using a vector twice |

**Date**: |
Wed, 03 Sep 2008 18:36:00 +0100 |

**User-agent**: |
Wanderlust/2.14.0 (Africa) Emacs/22.2 Mule/5.0 (SAKAKI) |

At Wed, 03 Sep 2008 11:37:51 -0500,
Alejandro Cruz Marcelo wrote:
>* When using the funciton gsl_blas_dgemv to perform the operation*
>* x = Ax*
>* it returns x equal to 0. I guess we are not supposed to use the same *
>* vector but that warning is not in the manual.*
>* However, the operation*
>* x = Ax + x*
>* it is performed properly.*
Thanks for the test program.
The two vectors x and y in "y = alpha * A * x + beta * y" must be
independent, this true of all BLAS functions in general.
I have added a note to the BLAS chapter to make this clearer.
--
Brian Gough
GNU Scientific Library -
http://www.gnu.org/software/gsl/