zlaqr1.f(3) LAPACK zlaqr1.f(3)NAMEzlaqr1.f-
SYNOPSIS
Functions/Subroutines
subroutine zlaqr1 (N, H, LDH, S1, S2, V)
ZLAQR1 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 zlaqr1 (integerN, complex*16, dimension( ldh, * )H, integerLDH,
complex*16S1, complex*16S2, complex*16, dimension( * )V)
ZLAQR1 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, ZLAQR1 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*16 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*16
S2
S2 is COMPLEX*16
S1 and S2 are the shifts defining K in (*) above.
V
V is COMPLEX*16 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 zlaqr1.f.
Author
Generated automatically by Doxygen for LAPACK from the source code.
Version 3.4.2 Sat Nov 16 2013 zlaqr1.f(3)
