chpr2 (l)  Linux Manuals
chpr2: performs the hermitian rank 2 operation A := alpha*x*conjg( yaq ) + conjg( alpha )*y*conjg( xaq ) + A,
NAME
CHPR2  performs the hermitian rank 2 operation A := alpha*x*conjg( yaq ) + conjg( alpha )*y*conjg( xaq ) + A,SYNOPSIS
 SUBROUTINE CHPR2(UPLO,N,ALPHA,X,INCX,Y,INCY,AP)
 COMPLEX ALPHA
 INTEGER INCX,INCY,N
 CHARACTER UPLO
 COMPLEX AP(*),X(*),Y(*)
PURPOSE
CHPR2 performs the hermitian rank 2 operation
where alpha is a scalar, x and y are n element vectors and A is an
n by n hermitian 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 = aqUaq or aquaq The upper triangular part of A is supplied in AP.
UPLO = aqLaq or aqlaq 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  COMPLEX .
 On entry, ALPHA specifies the scalar alpha. Unchanged on exit.
 X  COMPLEX 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.
 Y  COMPLEX array of dimension at least
 ( 1 + ( n  1 )*abs( INCY ) ). Before entry, the incremented array Y must contain the n element vector y. Unchanged on exit.
 INCY  INTEGER.
 On entry, INCY specifies the increment for the elements of Y. INCY must not be zero. Unchanged on exit.
 AP  COMPLEX array of DIMENSION at least
 ( ( n*( n + 1 ) )/2 ). Before entry with UPLO = aqUaq or aquaq, the array AP must contain the upper triangular part of the hermitian 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 = aqLaq or aqlaq, the array AP must contain the lower triangular part of the hermitian 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. Note that the imaginary parts of the diagonal elements need not be set, they are assumed to be zero, and on exit they are set to zero.
FURTHER DETAILS
Level 2 Blas routine.
 Written on 22October1986.
Jack Dongarra, Argonne National Lab.
Jeremy Du Croz, Nag Central Office.
Sven Hammarling, Nag Central Office.
Richard Hanson, Sandia National Labs.