HP MLIB User's Guide Vol. 1 7th Ed.

218 HP MLIB User’s Guide

SGBMV/DGBMV/CGBMV/ZGBMV Matrix-vector multiply

Example 2 Form the REAL*8 matrix-vector product , where ρ is a real

scalar, A is a 6-by-9 real band matrix whose lower bandwidth is 1 and whose

upper bandwidth is 2. A is stored in an array AB whose dimensions are 10 by

10, x is a real vector 6 elements long stored in an array X of dimension 10, and y

is a real vector 9 elements long stored in an array Y, also of dimension 10.

INTEGER*4 M,N,KL,KU,LDAB

REAL*8 RHO,AB(10,10),X(10),Y(10)

M = 9

N = 6

KL = 1

KU = 2

LDAB = 10

CALL DGBMV (’TRANSPOSE’,M,N,KL,KU,-RHO,AB,LDAB,X,1,0.5D0,Y,1)

---

y ρA

x–=