claqr1.f3

!>
!>      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.
!> 

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 (*).
!> 

Univ. of Tennessee

Univ. of California Berkeley

Univ. of Colorado Denver

NAG Ltd.

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