table of contents
other versions
- jessie 3.5.0-4
- jessie-backports 3.7.0-1~bpo8+1
- stretch 3.7.0-2
dlaqr1.f(3) | LAPACK | dlaqr1.f(3) |
NAME¶
dlaqr1.f -SYNOPSIS¶
Functions/Subroutines¶
subroutine dlaqr1 (N, H, LDH, SR1, SI1, SR2, SI2, V)
Function/Subroutine Documentation¶
subroutine dlaqr1 (integerN, double precision, dimension( ldh, * )H, integerLDH, double precisionSR1, double precisionSI1, double precisionSR2, double precisionSI2, double precision, dimension( * )V)¶
DLAQR1 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, DLAQR1 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.
N
Author:
N is integer Order of the matrix H. N must be either 2 or 3.H
H is DOUBLE PRECISION 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.NSR1
SR1 is DOUBLE PRECISIONSI1
SI1 is DOUBLE PRECISIONSR2
SR2 is DOUBLE PRECISIONSI2
SI2 is DOUBLE PRECISION The shifts in (*).V
V is DOUBLE PRECISION array of 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.
Date:
September 2012
Contributors:
Karen Braman and Ralph Byers, Department of Mathematics,
University of Kansas, USA
Definition at line 122 of file dlaqr1.f.
Author¶
Generated automatically by Doxygen for LAPACK from the source code.Wed Oct 15 2014 | Version 3.4.2 |