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

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

     DOUBLE PRECISION ALPHA, BETA

     INTEGER INCX, INCY, LDA, N

     CHARACTER*1 UPLO

     DOUBLE PRECISION A( LDA, * ), X( * ), Y( * )



     #include <sunperf.h>

     void dsymv(char uplo, int n, double alpha, double  *da,  int
               lda,  double  *dx,  int  incx, double beta, double
               *dy, int incy) ;

PURPOSE
     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.


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     - DOUBLE PRECISION.
               On  entry,  ALPHA  specifies  the  scalar   alpha.
               Unchanged on exit.

     A         - DOUBLE PRECISION 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 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         - DOUBLE PRECISION 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      - DOUBLE PRECISION.
               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         - DOUBLE PRECISION 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.

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