claqr1.f man page

claqr1.f —

Synopsis

Functions/Subroutines

subroutine claqr1 (N, H, LDH, S1, S2, V)
CLAQR1 sets a scalar multiple of the first column of the product of 2-by-2 or 3-by-3 matrix H and specified shifts.

Function/Subroutine Documentation

subroutine claqr1 (integerN, complex, dimension( ldh, * )H, integerLDH, complexS1, complexS2, complex, dimension( * )V)

CLAQR1 sets a scalar multiple of the first column of the product of 2-by-2 or 3-by-3 matrix H and specified shifts.

Purpose:

Given a 2-by-2 or 3-by-3 matrix H, CLAQR1 sets v to a
scalar multiple of the first column of the product

(*)  K = (H - s1*I)*(H - s2*I)

scaling to avoid overflows and most underflows.

This is useful for starting double implicit shift bulges
in the QR algorithm.

Parameters:

N

N is integer
    Order of the matrix H. N must be either 2 or 3.

H

H is COMPLEX array of dimension (LDH,N)
    The 2-by-2 or 3-by-3 matrix H in (*).

LDH

LDH is integer
    The leading dimension of H as declared in
    the calling procedure.  LDH.GE.N

S1

S1 is COMPLEX

S2

S2 is COMPLEX

S1 and S2 are the shifts defining K in (*) above.

V

V is COMPLEX array of dimension N
    A scalar multiple of the first column of the
    matrix K in (*).

Author:

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

Date:

September 2012

Contributors:

Karen Braman and Ralph Byers, Department of Mathematics, University of Kansas, USA

Definition at line 108 of file claqr1.f.

Author

Generated automatically by Doxygen for LAPACK from the source code.

Referenced By

claqr1(3) is an alias of claqr1.f(3).

Sat Nov 16 2013 Version 3.4.2 LAPACK