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CHPR(1) BLAS routine CHPR(1)

NAME

CHPR - performs the hermitian rank 1 operation A := alpha*x*conjg( x' ) + A,

SYNOPSIS

REAL ALPHA INTEGER INCX,N CHARACTER UPLO COMPLEX AP(*),X(*)

PURPOSE

CHPR performs the hermitian rank 1 operation

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

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.

On entry, N specifies the order of the matrix A. N must be at least zero. Unchanged on exit.
On entry, ALPHA specifies the scalar alpha. Unchanged on exit.
( 1 + ( n - 1 )*abs( INCX ) ). Before entry, the incremented array X must contain the n element vector x. Unchanged on exit.
On entry, INCX specifies the increment for the elements of X. INCX must not be zero. Unchanged on exit.
( ( n*( n + 1 ) )/2 ). Before 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. Before 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. 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 22-October-1986.
Jack Dongarra, Argonne National Lab.
Jeremy Du Croz, Nag Central Office.
Sven Hammarling, Nag Central Office.
Richard Hanson, Sandia National Labs.

November 2008 BLAS routine