DSYMV  performs the matrix-vector  operation


    y := alpha*A*x + beta*y,


 where alpha and beta are scalars, x and y are n element vectors and


 A is an n by n symmetric matrix.

UPLO

          UPLO is 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.

N

          N is INTEGER


           On entry, N specifies the order of the matrix A.


           N must be at least zero.

ALPHA

          ALPHA is DOUBLE PRECISION.


           On entry, ALPHA specifies the scalar alpha.

A

          A is DOUBLE PRECISION 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.

LDA

          LDA is 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 ).

X

          X is DOUBLE PRECISION array, dimension at least


           ( 1 + ( n - 1 )*abs( INCX ) ).


           Before entry, the incremented array X must contain the n


           element vector x.

INCX

          INCX is INTEGER


           On entry, INCX specifies the increment for the elements of


           X. INCX must not be zero.

BETA

          BETA is DOUBLE PRECISION.


           On entry, BETA specifies the scalar beta. When BETA is


           supplied as zero then Y need not be set on input.

Y

          Y is DOUBLE PRECISION 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

          INCY is INTEGER


           On entry, INCY specifies the increment for the elements of


           Y. INCY must not be zero.

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

December 2016

  Level 2 Blas routine.


  The vector and matrix arguments are not referenced when N = 0, or M = 0


  -- 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.