sspr

```SSPR(1)                          BLAS routine                          SSPR(1)

NAME
SSPR - performs the symmetric rank 1 operation   A := alpha*x*x' + A,

SYNOPSIS
SUBROUTINE SSPR(UPLO,N,ALPHA,X,INCX,AP)

REAL                                ALPHA

INTEGER                             INCX,N

CHARACTER                           UPLO

REAL                                AP(*),X(*)

PURPOSE
SSPR    performs the symmetric rank 1 operation

where alpha is a real scalar, x is an n element vector and A is an n by
n symmetric matrix, supplied in packed form.

ARGUMENTS
UPLO   - 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.

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

X      - REAL             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.

AP     - REAL             array of 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. 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 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. On exit, the array AP is overwritten by
the lower triangular part of the updated matrix.

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                         SSPR(1)```