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# zher

## man page of zher

### zher: perform the hermitian rank 1 operation A := alpha*x*conjg( x' ) + A,

```NAME
ZHER  - perform the hermitian rank 1 operation   A := alpha*x*conjg( x'
) + A,

SYNOPSIS
SUBROUTINE ZHER ( UPLO, N, ALPHA, X, INCX, A, LDA )

DOUBLE      PRECISION ALPHA

INTEGER     INCX, LDA, N

CHARACTER*1 UPLO

COMPLEX*16  A( LDA, * ), X( * )

PURPOSE
ZHER   performs the hermitian rank 1 operation

where alpha is a real scalar, x is an n element vector 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  - DOUBLE PRECISION.
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 vector x.  Unchanged on exit.

INCX   - INTEGER.
On entry, INCX specifies the increment for the  elements  of  X.
INCX 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 contain 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
imaginary 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.

ZHER(3)
```