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## NAME

```       CHEMV - perform the matrix-vector operation   y := alpha*A*x + beta*y,

```

## SYNOPSIS

```       SUBROUTINE CHEMV ( UPLO, N, ALPHA, A, LDA, X, INCX, BETA, Y, INCY )

COMPLEX      ALPHA, BETA

INTEGER      INCX, INCY, LDA, N

CHARACTER*1  UPLO

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

```

## PURPOSE

```       CHEMV  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.

```

## 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         .
On entry, ALPHA specifies the scalar alpha.  Unchanged on  exit.

A      - COMPLEX          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          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         .
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          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.

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.
```