C Library Functions - dspr2 (3)
NAME
dspr2(3f) - [BLAS:DOUBLE_BLAS_LEVEL2]
CONTENTS
Synopsis
Definition
Options
Ap
Authors
Further Details
See Also
SYNOPSIS
subroutine dspr2(uplo,n,alpha,x,incx,y,incy,ap)
.. Scalar Arguments .. double precision,intent(in) :: alpha integer,intent(in) :: incx,incy,n character,intent(in) :: uplo .. .. Array Arguments .. double precision,intent(inout) :: ap(*) double precision,intent(in) :: x(*),y(*) ..
DEFINITION
DSPR2 performs the symmetric rank 2 operation
A := alpha*x*y**T + alpha*y*x**T + 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.
OPTIONS
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.
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.
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.
INCY
INCY is INTEGER On entry, INCY specifies the increment for the elements of Y. INCY must not be zero.
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. 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.
AUTHORS
o Univ. of Tennessee o Univ. of California Berkeley o Univ. of Colorado Denver o NAG Ltd. date:December 2016
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.
SEE ALSO
Online html documentation available at http://www.netlib.org/lapack/explore-html/
| Nemo Release 3.1 | dspr2 (3) | February 23, 2025 |
