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

274 HP MLIB User’s Guide

SSYMV/DSYMV/CHEMV/ZHEMV Matrix-vector multiply

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

symmetric matrix whose upper triangle is stored in the upper triangle of an

array A whose dimensions are 10-by-10, x is a real vector 9 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 UPLO

INTEGER*4 N,LDA,INCX,INCY

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

UPLO = ’U’

N = 9

ALPHA = 1.0

BETA = 0.0

LDA = 10

INCX = 1

INCY = 1

CALL SSYMV (UPLO,N,ALPHA,A,LDA,X,INCX,BETA,Y,INCY)

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

complex scalar, A is a 9-by-9 complex Hermitian matrix whose lower triangle is

stored in the lower triangle of an array A whose dimensions are 10-by-10, x is a

complex vector 9 elements long stored in an array X of dimension 10, and y is a

complex vector 9 elements long stored in an array Y, also of dimension 10.

INTEGER*4 N,LDA

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

N = 9

LDA = 10

CALL CHEMV (’LOWER’,N,-RHO,A,LDA,X,1,(0.5,0.0),Y,1)

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y ρAx–=