claqr1.f

Section: LAPACK (3)
Updated: Tue Nov 14 2017
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NAME

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.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, 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:

June 2017

Contributors:

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

Definition at line 109 of file claqr1.f.  

Author

Generated automatically by Doxygen for LAPACK from the source code.


 

Index

NAME
SYNOPSIS
Functions/Subroutines
Function/Subroutine Documentation
subroutine claqr1 (integer N, complex, dimension( ldh, * ) H, integer LDH, complex S1, complex S2, complex, dimension( * ) V)
Author
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