chpr

NAME

chpr - perform the hermitian rank 1 operation A := alpha*x*conjg( x' ) + A

SYNOPSIS 

  SUBROUTINE CHPR( UPLO, N, ALPHA, X, INCX, A)
  CHARACTER * 1 UPLO
  COMPLEX X(*), A(*)
  INTEGER N, INCX
  REAL ALPHA
 
  SUBROUTINE CHPR_64( UPLO, N, ALPHA, X, INCX, A)
  CHARACTER * 1 UPLO
  COMPLEX X(*), A(*)
  INTEGER*8 N, INCX
  REAL ALPHA

F95 INTERFACE 

  SUBROUTINE HPR( UPLO, [N], ALPHA, X, [INCX], A)
  CHARACTER(LEN=1) :: UPLO
  COMPLEX, DIMENSION(:) :: X, A
  INTEGER :: N, INCX
  REAL :: ALPHA
 
  SUBROUTINE HPR_64( UPLO, [N], ALPHA, X, [INCX], A)
  CHARACTER(LEN=1) :: UPLO
  COMPLEX, DIMENSION(:) :: X, A
  INTEGER(8) :: N, INCX
  REAL :: ALPHA

C INTERFACE

#include <sunperf.h>

void chpr(char uplo, int n, float alpha, complex *x, int incx, complex *a);

void chpr_64(char uplo, long n, float alpha, complex *x, long incx, complex *a);

PURPOSE

chpr performs the hermitian rank 1 operation A := alpha*x*conjg( x' ) + A where alpha is a real scalar, x is an n element vector and A is an n by n hermitian matrix, supplied in packed form.

ARGUMENTS

* UPLO (input)
On entry, UPLO specifies whether the upper or lower triangular part of the matrix A is supplied in the packed array A as follows:

UPLO = 'U' or 'u' The upper triangular part of A is supplied in A.

UPLO = 'L' or 'l' The lower triangular part of A is supplied in A.

Unchanged on exit.

* N (input)
On entry, N specifies the order of the matrix A. N >= 0. Unchanged on exit.

* ALPHA (input)
On entry, ALPHA specifies the scalar alpha. Unchanged on exit.

* X (input)
( 1 + ( n - 1 )*abs( INCX ) ). Before entry, the incremented array X must contain the n element vector x. Unchanged on exit.

* INCX (input)
On entry, INCX specifies the increment for the elements of X. INCX <> 0. Unchanged on exit.

* A (input/output)
( ( n*( n + 1 ) )/2 ). Before entry with UPLO = 'U' or 'u', the array A must contain the upper triangular part of the hermitian matrix packed sequentially, column by column, so that A( 1 ) contains a( 1, 1 ), A( 2 ) and A( 3 ) contain a( 1, 2 ) and a( 2, 2 ) respectively, and so on. On exit, the array A is overwritten by the upper triangular part of the updated matrix. Before entry with UPLO = 'L' or 'l', the array A must contain the lower triangular part of the hermitian matrix packed sequentially, column by column, so that A( 1 ) contains a( 1, 1 ), A( 2 ) and A( 3 ) contain a( 2, 1 ) and a( 3, 1 ) respectively, and so on. On exit, the array A 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.