Contents

• NAME
• SYNOPSIS
  • F95 INTERFACE
  • C INTERFACE
• PURPOSE
• ARGUMENTS

NAME

     dspr2 - perform  the  symmetric  rank  2  operation    A  :=
     alpha*x*y' + alpha*y*x' + A

SYNOPSIS

     SUBROUTINE DSPR2(UPLO, N, ALPHA, X, INCX, Y, INCY, AP)

     CHARACTER * 1 UPLO
     INTEGER N, INCX, INCY
     DOUBLE PRECISION ALPHA
     DOUBLE PRECISION X(*), Y(*), AP(*)

     SUBROUTINE DSPR2_64(UPLO, N, ALPHA, X, INCX, Y, INCY, AP)

     CHARACTER * 1 UPLO
     INTEGER*8 N, INCX, INCY
     DOUBLE PRECISION ALPHA
     DOUBLE PRECISION X(*), Y(*), AP(*)

  F95 INTERFACE
     SUBROUTINE SPR2(UPLO, [N], ALPHA, X, [INCX], Y, [INCY], AP)

     CHARACTER(LEN=1) :: UPLO
     INTEGER :: N, INCX, INCY
     REAL(8) :: ALPHA
     REAL(8), DIMENSION(:) :: X, Y, AP

     SUBROUTINE SPR2_64(UPLO, [N], ALPHA, X, [INCX], Y, [INCY], AP)

     CHARACTER(LEN=1) :: UPLO
     INTEGER(8) :: N, INCX, INCY
     REAL(8) :: ALPHA
     REAL(8), DIMENSION(:) :: X, Y, AP

  C INTERFACE
     #include <sunperf.h>

     void dspr2(char uplo, int n, double alpha,  double  *x,  int
               incx, double *y, int incy, double *ap);

     void dspr2_64(char uplo, long n, double  alpha,  double  *x,
               long incx, double *y, long incy, double *ap);

PURPOSE

     dspr2  performs  the  symmetric  rank  2  operation   A   :=
     alpha*x*y'  + alpha*y*x' + A, where alpha is a scalar, x and
     y are n element vectors and A is an n by n symmetric matrix,
     supplied in packed form.

ARGUMENTS

     UPLO (input)
               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.

               Unchanged on exit.

     N (input)
               On entry, N specifies the order of the  matrix  A.
               N >= 0.  Unchanged on exit.

     ALPHA (input)
               On  entry,  ALPHA  specifies  the  scalar   alpha.
               Unchanged on exit.

     X (input)
               Double  precision  array,  dimension  (1  +  (n  -
               1)*abs(INCX))  Before entry, the incremented array
               X must contain the n element vector x.   Unchanged
               on exit.

     INCX (input)
               On entry, INCX specifies  the  increment  for  the
               elements of X. INCX <> 0.  Unchanged on exit.

     Y (input)
               Double  precision  array,  dimension  (1  +  (n  -
               1)*abs(INCY))  Before entry, the incremented array
               Y must contain the n element vector y.   Unchanged
               on exit.

     INCY (input)
               On entry, INCY specifies  the  increment  for  the
               elements of Y. INCY <> 0.  Unchanged on exit.
     AP (input/output)
               Double precision array, dimension (( n*(n + 1))/2)
               Before entry with  UPLO = 'U' or 'u', the array AP
               must contain the upper triangular part of the sym-
               metric   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. On exit, the array AP  is
               overwritten  by  the  upper triangular part of the
               updated matrix.  Before entry with UPLO =  'L'  or
               'l',  the array AP must contain the lower triangu-
               lar part of the symmetric  matrix  packed  sequen-
               tially, 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. On exit,
               the array AP is overwritten by the lower  triangu-
               lar part of the updated matrix.