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SRC/lapack_64_obj/claqr1.f(3) Library Functions Manual SRC/lapack_64_obj/claqr1.f(3)

NAME

SRC/lapack_64_obj/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 (integer n, complex, dimension( ldh, * ) h, integer ldh, complex s1, complex s2, 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, 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 >= N
!>

S1

!>          S1 is COMPLEX
!>

S2

!>          S2 is COMPLEX
!>
!>          S1 and S2 are the shifts defining K in (*) above.
!>

V

!>          V is COMPLEX array, 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.

Contributors:

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

Definition at line 107 of file claqr1.f.

Author

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