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)