Matrix-vector multiply

SGBMV/DGBMV/CGBMV/ZGBMV

kl

The lower bandwidth of A, that is, the number of

 

nonzero diagonals below the principal diagonal in the

 

band, 0 ≤ kl < n.

ku

The upper bandwidth of A, that is, the number of

 

nonzero diagonals above the principal diagonal in the

 

band, 0 ≤ ku < n.

alpha

The scalar α. If alpha = 0, the subprograms compute

 

y ← βy without referencing ab or x.

ab

Array containing the m-by-nband matrix A in the

 

compressed form described above. If aij is in the band,

 

it is stored in ab(ku+1+i−j,j). The columns of A are

 

stored in the columns of ab, and the diagonals of A are

 

stored in rows 1 through kl+ku+1.

ldab

The leading dimension of array ab as declared in the

 

calling program unit, with ldab ≥ kl+ku+1.

Chapter 3 Basic Matrix Operations 215