C Library Functions - cher (3)

NAME

cher(3f) - [BLAS:COMPLEX_BLAS_LEVEL2] A := A + alpha*CX*CONJUGATE-TRANSPOSE(CX); ==> A a (square) hermitian matrix. (performs the hermitian rank 1 operation)

Synopsis
Definition
Options
A
Authors
Further Details
See Also

SYNOPSIS

subroutine cher(uplo,n,alpha,x,incx,a,lda)

      .. Scalar Arguments ..
      real,intent(in)       :: alpha
      integer,intent(in)    :: incx,lda,n
      character,intent(in)  :: uplo
      ..
      .. Array Arguments ..
      complex,intent(inout) :: a(lda,*)
      complex,intent(in)    :: x(*)
      ..

DEFINITION

CHER performs the hermitian rank 1 operation
    A := alpha*x*x**H + A,
where alpha is a real scalar, x is an n element vector and A is an n by n hermitian matrix.

OPTIONS

UPLO

UPLO is CHARACTER*1 On entry, UPLO specifies whether the upper or lower triangular part of the array A is to be referenced as follows:

UPLO = ’U’ or ’u’ Only the upper triangular part of A is to be referenced.

UPLO = ’L’ or ’l’ Only the lower triangular part of A is to be referenced.

N

N is INTEGER On entry, N specifies the order of the matrix A. N must be at least zero.

ALPHA

ALPHA is REAL On entry, ALPHA specifies the scalar alpha.

X

X is COMPLEX 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.

A

A is COMPLEX array, dimension ( LDA, N ) Before entry with UPLO = ’U’ or ’u’, the leading n by n upper triangular part of the array A must contain the upper triangular part of the hermitian matrix and the strictly lower triangular part of A is not referenced. On exit, the upper triangular part of the array A is overwritten by the upper triangular part of the updated matrix. Before entry with UPLO = ’L’ or ’l’, the leading n by n lower triangular part of the array A must contain the lower triangular part of the hermitian matrix and the strictly upper triangular part of A is not referenced. On exit, the lower triangular part of 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.

LDA

LDA is INTEGER On entry, LDA specifies the first dimension of A as declared in the calling (sub) program. LDA must be at least max( 1, n ).

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.