Bug#694625: libblas3gf: DGEMV does not handle properly N=0

[Christophe TROESTLER]

On Wed, 28 Nov 2012 15:20:33 +0100, Sylvestre Ledru wrote:
> 
> severity 694625 normal
> thanks
> 
> Bonjour Christophe!

Salut Sylvestre !

> On 28/11/2012 15:05, Christophe TROESTLER wrote:
> 
> > Dear Maintainer,
> > 
> > The routine DGEMV (with TRANS = 'N') is supposed to perform the
> > operation
> > 
> >     y ← beta * y + alpha * A * x
> > 
> > where the matrix A has dimensions M×N.  In particular, if N=0 (and M >
> > 0), A * x is the null vector (all elements are given by sums on an
> > empty set of indices).  Consequently, if N = 0, the operation should
> > be
> > 
> >     y ← beta * y
> > 
> > and NOT leave y untouched.  For your convenience, I have attached a
> > program demonstrating the latter (wrong) behavior.
> 
> I am getting:
>    1.0000000000000000
>    2.0000000000000000
> What should I get ?

2.
4.

(beta=2 in the code).