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

Chapter 3 Basic Matrix Operations 353

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-n real 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 αxy

∗

ayx

∗

βA with A=A

∗

++←