[ Previous  Next  Table of Contents  Index  Library Home 
Legal 
Search ]
Technical Reference: Base Operating System and Extensions , Volume 2
Performs the Hermitian rank 2
operation.
BLAS Library
(libblas.a)
SUBROUTINE CHPR2 (UPLO, N, ALPHA,
X, INCX, Y, INCY, AP)
COMPLEX ALPHA
INTEGER INCX, INCY, N
CHARACTER*1 UPLO
COMPLEX AP(*), X(*), Y(*)
SUBROUTINE
ZHPR2
COMPLEX*16 ALPHA
INTEGER INCX,INCY,N
CHARACTER*1 UPLO
COMPLEX*16 AP(*), X(*), Y(*)
The CHPR2 or
ZHPR2 subroutine performs the Hermitian rank 2 operation:
A := alpha
* x * conjg( y' ) + conjg( alpha ) * y * conjg( x' ) +
A
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.
UPLO
 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
 On entry, N specifies the order of the matrix
A; N must be at least 0; unchanged on
exit.

ALPHA
 On entry, ALPHA specifies the scalar alpha; unchanged on
exit.

X
 A vector of dimension at least (1 + (N1) *
abs(INCX) ); on entry, the incremented array X must
contain the N element vector x; unchanged on exit.

INCX
 On entry, INCX specifies the increment for the elements of
X; INCX must not be 0; unchanged on
exit.

Y
 A vector of dimension at least (1 + (N1) * abs(
INCY ) ); on entry, the incremented array Y must
contain the N element vector y; unchanged on exit.

INCY
 On entry, INCY specifies the increment for the elements of
Y; INCY must not be 0; unchanged on
exit.

AP
 A vector of dimension at least ( ( N * (N+1) )/2
); on entry with UPLO = 'U' or 'u', 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. On entry with UPLO = 'L' or
'l', 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. The imaginary parts of the
diagonal elements need not be set, they are assumed to be 0, and on exit they
are set to 0.

[ Previous  Next  Table of Contents  Index 
Library Home 
Legal 
Search ]