Triangular banded matrix-vector multiply

F_STBMV/F_DTBMV/F_CTBMV/F_ZTBMV

 

N

Number of rows and columns in matrix A, and

 

 

elements of vector X. n > 0. If n ≤ 0 , the subprograms

 

 

do not reference A or X.

 

K

The number of non zero diagonals above or below the

 

 

principal diagonal.

 

ALPHA

The scalar ALPHA.

 

A

REAL or COMPLEX array, dimension (LDA, N).

 

LDA

Leading dimension of array A. If lda < k + 1, an error

 

 

condition is generated.

 

X

REAL or COMPLEX array, minimum length

 

 

(N - 1) x incx + 1.

 

INCX

Increment for the array x. A vector x having component

 

 

xi, i = 1,..., n, is stored in an array X() with increment

 

 

argument incx. If incx > 0 then xi is stored in

 

 

X (1 + (i - 1) x incx). If incx < 0 then xiis stored in

 

 

X (1 + (N - i) x incx). incx = 0 is an illegal value.

Output

X

The updated X vector replaces the input.

Chapter 3 Basic Matrix Operations 399