DSPMV  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, supplied in packed form.

UPLO

          UPLO is CHARACTER*1


           On entry, UPLO specifies whether the upper or lower


           triangular part of the matrix A is supplied in the packed


           array AP as follows:


              UPLO = 'U' or 'u'   The upper triangular part of A is


                                  supplied in AP.


              UPLO = 'L' or 'l'   The lower triangular part of A is


                                  supplied in AP.

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.

AP

          AP is DOUBLE PRECISION array, dimension at least


           ( ( n*( n + 1 ) )/2 ).


           Before entry with UPLO = 'U' or 'u', the array AP must


           contain the upper triangular part of the symmetric matrix


           packed sequentially, column by column, so that AP( 1 )


           contains a( 1, 1 ), AP( 2 ) and AP( 3 ) contain a( 1, 2 )


           and a( 2, 2 ) respectively, and so on.


           Before entry with UPLO = 'L' or 'l', the array AP must


           contain the lower triangular part of the symmetric matrix


           packed sequentially, column by column, so that AP( 1 )


           contains a( 1, 1 ), AP( 2 ) and AP( 3 ) contain a( 2, 1 )


           and a( 3, 1 ) respectively, and so on.

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.