CSYMV (3lapack)

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

SYNOPSIS

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

      CHARACTER     UPLO

      INTEGER       INCX, INCY, LDA, N

      COMPLEX       ALPHA, BETA

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

PURPOSE

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

  A      - COMPLEX array, 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 symmetric 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 symmetric matrix and the strictly upper
         triangular part of A is not referenced.  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, 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, 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.