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

236 HP MLIB User’s Guide

SGEMV/DGEMV/CGEMV/ZGEMV Matrix-vector multiply

Example 1 Form the REAL*4 matrix-vector product y = Ax, where A is a 9-by-6 real

matrix stored in an array A 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.

CHARACTER*1 TRANS

INTEGER*4 M,N,LDA,INCX,INCY

REAL*4 ALPHA,BETA,A(10,10),X(10),Y(10)

TRANS = ’N’

M = 9

N = 6

ALPHA = 1.0

BETA = 0.0

LDA = 10

INCX = 1

INCY = 1

CALL SGEMV (TRANS,M,N,ALPHA,A,LDA,X,INCX,BETA,Y,INCY)

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

scalar, A is a 6-by-9 real matrix stored in an array A 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,LDA

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

M = 9

N = 6

LDA = 10

CALL DGEMV (’TRANSPOSE’,M,N,-RHO,A,LDA,X,1,0.5D0,Y,1)

---

y ρA

x–=