slaqr1.f(3) LAPACK slaqr1.f(3)NAMEslaqr1.f-
SYNOPSIS
Functions/Subroutines
subroutine slaqr1 (N, H, LDH, SR1, SI1, SR2, SI2, V)
SLAQR1 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 slaqr1 (integerN, real, dimension( ldh, * )H, integerLDH,
realSR1, realSI1, realSR2, realSI2, real, dimension( * )V)
SLAQR1 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, SLAQR1 sets v to a
scalar multiple of the first column of the product
(*) K = (H - (sr1 + i*si1)*I)*(H - (sr2 + i*si2)*I)
scaling to avoid overflows and most underflows. It
is assumed that either
1) sr1 = sr2 and si1 = -si2
or
2) si1 = si2 = 0.
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 REAL 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
SR1
SR1 is REAL
SI1
SI1 is REAL
SR2
SR2 is REAL
SI2
SI2 is REAL
The shifts in (*).
V
V is REAL 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 122 of file slaqr1.f.
Author
Generated automatically by Doxygen for LAPACK from the source code.
Version 3.4.2 Sat Nov 16 2013 slaqr1.f(3)
