Man Linux: Main Page and Category List

NAME

```       DSPR - perform the symmetric rank 1 operation   A := alpha*x*x’ + A,

```

SYNOPSIS

```       SUBROUTINE DSPR ( UPLO, N, ALPHA, X, INCX, AP )

DOUBLE      PRECISION ALPHA

INTEGER     INCX, N

CHARACTER*1 UPLO

DOUBLE      PRECISION AP( * ), X( * )

```

PURPOSE

```       DSPR    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.

```

PARAMETERS

```       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  - DOUBLE PRECISION.
On  entry, ALPHA specifies the scalar alpha.  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.

AP     - DOUBLE PRECISION 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.

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.
```