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zlaqr1.f(3) LAPACK zlaqr1.f(3)NAMEzlaqr1.f-SYNOPSISFunctions/Subroutines subroutine zlaqr1 (N, H, LDH, S1, S2, 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.Function/Subroutine Documentation 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. Purpose: 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. Parameters: N N is integer Order of the matrix H. N must be either 2 or 3. H H is COMPLEX*16 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*16 S2 S2 is COMPLEX*16 S1 and S2 are the shifts defining K in (*) above. V V is COMPLEX*16 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 zlaqr1.f.AuthorGenerated automatically by Doxygen for LAPACK from the source code.Version 3.4.2Tue Sep 25 2012 zlaqr1.f(3)

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