# zhemv

```ZHEMV(1)                         BLAS routine                         ZHEMV(1)

NAME
ZHEMV - performs the matrix-vector operation   y := alpha*A*x + beta*y,

SYNOPSIS
SUBROUTINE ZHEMV(UPLO,N,ALPHA,A,LDA,X,INCX,BETA,Y,INCY)

DOUBLE                                              COMPLEX
ALPHA,BETA

INTEGER                                             INCX,INCY,LDA,N

CHARACTER                                           UPLO

DOUBLE                                              COMPLEX
A(LDA,*),X(*),Y(*)

PURPOSE
ZHEMV  performs the matrix-vector  operation

where alpha and beta are scalars, x and y are n element vectors and A
is an n by n hermitian matrix.

ARGUMENTS
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.

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.  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.
Note that the imaginary parts of the diagonal elements need not
be set and are assumed to be zero.  Unchanged on exit.

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.

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.

BETA   - COMPLEX*16      .
On entry, BETA specifies the scalar beta. When BETA is supplied
as zero then Y need not be set on input.  Unchanged on exit.

Y      - COMPLEX*16       array of dimension at least
( 1 + ( n - 1 )*abs( INCY ) ).  Before entry, the incremented
array Y must contain the n element vector y. On exit, Y is
overwritten by the updated vector y.

INCY   - INTEGER.
On entry, INCY specifies the increment for the elements of Y.
INCY must not be zero.  Unchanged on exit.

FURTHER DETAILS
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.

BLAS routine                     November 2008                        ZHEMV(1)```