claqr1.f - Man Page
SRC/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 (integer n, complex, dimension( ldh, * ) h, integer ldh, complex s1, complex s2, 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, 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 >= N
S1
S1 is COMPLEX
S2
S2 is COMPLEX S1 and S2 are the shifts defining K in (*) above.
V
V is COMPLEX array, 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.
- Contributors:
Karen Braman and Ralph Byers, Department of Mathematics, University of Kansas, USA
Definition at line 106 of file claqr1.f.
Author
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Referenced By
The man page claqr1(3) is an alias of claqr1.f(3).
Tue Nov 28 2023 12:08:41 Version 3.12.0 LAPACK