claqr1.f (3) Linux Manual Page

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

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