Hermitian rank-2 update

 

 

 

F_CHPR2/F_ZHPR2

Input

UPLO

Specifies whether a triangular matrix is upper or lower

 

 

triangular. Use either BLAS_UPPER or BLAS_LOWER.

 

N

Number of elements of vector x.

 

ALPHA

REAL scalar ALPHA.

 

X

COMPLEX array, minimum length

 

 

(N - 1) x incx + 1.

 

INCX

Increment for the array x. A vector x having component

 

 

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

 

 

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

 

 

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

 

 

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

 

Y

COMPLEX array, minimum length

 

 

(N - 1) x incy + 1.

 

INCY

Increment for the array y. A vector y having component

 

 

y(i), i = 1,..., n, is stored in an array Y() with increment

 

 

argument incy. If incy > 0 then (i) is stored in

 

 

Y(1 + (i - 1) x incy). If incy < 0 then (i) is stored in

 

 

Y(1 + (N - i) x incy). incy = 0 is an illegal value.

 

BETA

COMPLEX scalar BETA.

 

AP

Complex array, dimension (LDA, N). Contains the

 

 

upper or lower triangle, as specified by uplo of an

 

 

n-by-nreal symmetric or complex Hermitian matrix A,

 

 

stored by columns in packed form.

Output

AP

The upper or lower triangle of the updated A matrix, as

 

 

specified by uplo, replaces the input.

 

 

A ← αx y∗ +

a

yx∗ + βA with A=A∗

Chapter 3 Basic Matrix Operations 353