ZHER2 - perform the hermitian rank 2 operation A :=
alpha*x*conjg( y' ) + conjg( alpha )*y*conjg( x' ) + A,
SYNOPSIS
SUBROUTINE ZHER2 ( UPLO, N, ALPHA, X, INCX, Y, INCY, A,
LDA )
COMPLEX*16 ALPHA
INTEGER INCX, INCY, LDA, N
CHARACTER*1 UPLO
COMPLEX*16 A( LDA, * ), X( * ), Y( * )
PURPOSE
ZHER2 performs the hermitian rank 2 operation
where alpha is a scalar, x and y are n element vectors and
A is an n by n hermitian matrix.
PARAMETERS
UPLO - CHARACTER*1.
On entry, UPLO specifies whether the upper or lower
triangular part of the array A is to be referenced
as follows:
UPLO = 'U' or 'u' Only the upper triangular part
of A is to be referenced.
UPLO = 'L' or 'l' Only the lower triangular part
of A is to be referenced.
Unchanged on exit.
N - INTEGER.
On entry, N specifies the order of the matrix A. N
must be at least zero. Unchanged on exit.
ALPHA - COMPLEX*16 .
On entry, ALPHA specifies the scalar alpha.
Unchanged on exit.
X - COMPLEX*16 array of dimension at least
( 1 + ( n - 1 )*abs( INCX ) ). Before entry, the
incremented array X must contain the n element vec
tor x. Unchanged on exit.
INCX - INTEGER.
On entry, INCX specifies the increment for the ele
ments of X. INCX must not be zero. Unchanged on
exit.
( 1 + ( n - 1 )*abs( INCY ) ). Before entry, the
incremented array Y must contain the n element vec
tor y. Unchanged on exit.
INCY - INTEGER.
On entry, INCY specifies the increment for the ele
ments of Y. INCY must not be zero. Unchanged on
exit.
A - COMPLEX*16 array of DIMENSION ( LDA, n ).
Before entry with UPLO = 'U' or 'u', the leading n
by n upper triangular part of the array A must con
tain the upper triangular part of the hermitian
matrix and the strictly lower triangular part of A
is not referenced. On exit, the upper triangular
part of the array A is overwritten by the upper
triangular part of the updated matrix. Before
entry with UPLO = 'L' or 'l', the leading n by n
lower triangular part of the array A must contain
the lower triangular part of the hermitian matrix
and the strictly upper triangular part of A is not
referenced. On exit, the lower triangular part of
the array A is overwritten by the lower triangular
part of the updated matrix. Note that the imagi
nary parts of the diagonal elements need not be
set, they are assumed to be zero, and on exit they
are set to zero.
LDA - INTEGER.
On entry, LDA specifies the first dimension of A as
declared in the calling (sub) program. LDA must be
at least max( 1, n ). Unchanged on exit.
Level 2 Blas routine.
-- Written on 22-October-1986. Jack Dongarra,
Argonne National Lab. Jeremy Du Croz, Nag Central
Office. Sven Hammarling, Nag Central Office.
Richard Hanson, Sandia National Labs.
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