zlaqr1 (3) - Linux Man Pages
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.
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.
N is integer Order of the matrix H. N must be either 2 or 3.
H is COMPLEX*16 array of dimension (LDH,N) The 2-by-2 or 3-by-3 matrix H in (*).
LDH is integer The leading dimension of H as declared in the calling procedure. LDH.GE.N
S1 is COMPLEX*16
S2 is COMPLEX*16 S1 and S2 are the shifts defining K in (*) above.
V is COMPLEX*16 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
- September 2012
- Karen Braman and Ralph Byers, Department of Mathematics, University of Kansas, USA
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