Scroll to navigation

claqr1.f(3) LAPACK claqr1.f(3)

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 (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.
Wed Oct 15 2014 Version 3.4.2