SLATEC Routines --- CHPR2 ---


    Note: this is a BLAS routine and is not in libslatec.a

*DECK CHPR2
      SUBROUTINE CHPR2 (UPLO, N, ALPHA, X, INCX, Y, INCY, AP)
C***BEGIN PROLOGUE  CHPR2
C***PURPOSE  Perform the hermitian rank 2 operation.
C***LIBRARY   SLATEC (BLAS)
C***CATEGORY  D1B4
C***TYPE      COMPLEX (SHPR2-S, DHPR2-D, CHPR2-C)
C***KEYWORDS  LEVEL 2 BLAS, LINEAR ALGEBRA
C***AUTHOR  Dongarra, J. J., (ANL)
C           Du Croz, J., (NAG)
C           Hammarling, S., (NAG)
C           Hanson, R. J., (SNLA)
C***DESCRIPTION
C
C  CHPR2  performs the hermitian rank 2 operation
C
C     A := alpha*x*conjg( y') + conjg( alpha)*y*conjg( x') + A,
C
C  where alpha is a scalar, x and y are n element vectors and A is an
C  n by n hermitian matrix, supplied in packed form.
C
C  Parameters
C  ==========
C
C  UPLO   - CHARACTER*1.
C           On entry, UPLO specifies whether the upper or lower
C           triangular part of the matrix A is supplied in the packed
C           array AP as follows:
C
C              UPLO = 'U' or 'u'   The upper triangular part of A is
C                                  supplied in AP.
C
C              UPLO = 'L' or 'l'   The lower triangular part of A is
C                                  supplied in AP.
C
C           Unchanged on exit.
C
C  N      - INTEGER.
C           On entry, N specifies the order of the matrix A.
C           N must be at least zero.
C           Unchanged on exit.
C
C  ALPHA  - COMPLEX         .
C           On entry, ALPHA specifies the scalar alpha.
C           Unchanged on exit.
C
C  X      - COMPLEX          array of dimension at least
C           ( 1 + ( n - 1 )*abs( INCX ) ).
C           Before entry, the incremented array X must contain the n
C           element vector x.
C           Unchanged on exit.
C
C  INCX   - INTEGER.
C           On entry, INCX specifies the increment for the elements of
C           X. INCX must not be zero.
C           Unchanged on exit.
C
C  Y      - COMPLEX          array of dimension at least
C           ( 1 + ( n - 1 )*abs( INCY ) ).
C           Before entry, the incremented array Y must contain the n
C           element vector y.
C           Unchanged on exit.
C
C  INCY   - INTEGER.
C           On entry, INCY specifies the increment for the elements of
C           Y. INCY must not be zero.
C           Unchanged on exit.
C
C  AP     - COMPLEX          array of DIMENSION at least
C           ( ( n*( n + 1 ) )/2 ).
C           Before entry with  UPLO = 'U' or 'u', the array AP must
C           contain the upper triangular part of the hermitian matrix
C           packed sequentially, column by column, so that AP( 1 )
C           contains a( 1, 1 ), AP( 2 ) and AP( 3 ) contain a( 1, 2 )
C           and a( 2, 2 ) respectively, and so on. On exit, the array
C           AP is overwritten by the upper triangular part of the
C           updated matrix.
C           Before entry with UPLO = 'L' or 'l', the array AP must
C           contain the lower triangular part of the hermitian matrix
C           packed sequentially, column by column, so that AP( 1 )
C           contains a( 1, 1 ), AP( 2 ) and AP( 3 ) contain a( 2, 1 )
C           and a( 3, 1 ) respectively, and so on. On exit, the array
C           AP is overwritten by the lower triangular part of the
C           updated matrix.
C           Note that the imaginary parts of the diagonal elements need
C           not be set, they are assumed to be zero, and on exit they
C           are set to zero.
C
C***REFERENCES  Dongarra, J. J., Du Croz, J., Hammarling, S., and
C                 Hanson, R. J.  An extended set of Fortran basic linear
C                 algebra subprograms.  ACM TOMS, Vol. 14, No. 1,
C                 pp. 1-17, March 1988.
C***ROUTINES CALLED  LSAME, XERBLA
C***REVISION HISTORY  (YYMMDD)
C   861022  DATE WRITTEN
C   910605  Modified to meet SLATEC prologue standards.  Only comment
C           lines were modified.  (BKS)
C***END PROLOGUE  CHPR2