.TH "slaqr1.f" 3 "Wed Oct 15 2014" "Version 3.4.2" "LAPACK" \" -*- nroff -*- .ad l .nh .SH NAME slaqr1.f \- .SH SYNOPSIS .br .PP .SS "Functions/Subroutines" .in +1c .ti -1c .RI "subroutine \fBslaqr1\fP (N, H, LDH, SR1, SI1, SR2, SI2, V)" .br .RI "\fI\fBSLAQR1\fP sets a scalar multiple of the first column of the product of 2-by-2 or 3-by-3 matrix H and specified shifts\&. \fP" .in -1c .SH "Function/Subroutine Documentation" .PP .SS "subroutine slaqr1 (integerN, real, dimension( ldh, * )H, integerLDH, realSR1, realSI1, realSR2, realSI2, real, dimension( * )V)" .PP \fBSLAQR1\fP sets a scalar multiple of the first column of the product of 2-by-2 or 3-by-3 matrix H and specified shifts\&. .PP \fBPurpose: \fP .RS 4 .PP .nf Given a 2-by-2 or 3-by-3 matrix H, SLAQR1 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. .fi .PP .RE .PP \fBParameters:\fP .RS 4 \fIN\fP .PP .nf N is integer Order of the matrix H. N must be either 2 or 3. .fi .PP .br \fIH\fP .PP .nf H is REAL array of dimension (LDH,N) The 2-by-2 or 3-by-3 matrix H in (*). .fi .PP .br \fILDH\fP .PP .nf LDH is integer The leading dimension of H as declared in the calling procedure. LDH.GE.N .fi .PP .br \fISR1\fP .PP .nf SR1 is REAL .fi .PP .br \fISI1\fP .PP .nf SI1 is REAL .fi .PP .br \fISR2\fP .PP .nf SR2 is REAL .fi .PP .br \fISI2\fP .PP .nf SI2 is REAL The shifts in (*). .fi .PP .br \fIV\fP .PP .nf V is REAL array of dimension N A scalar multiple of the first column of the matrix K in (*). .fi .PP .RE .PP \fBAuthor:\fP .RS 4 Univ\&. of Tennessee .PP Univ\&. of California Berkeley .PP Univ\&. of Colorado Denver .PP NAG Ltd\&. .RE .PP \fBDate:\fP .RS 4 September 2012 .RE .PP \fBContributors: \fP .RS 4 Karen Braman and Ralph Byers, Department of Mathematics, University of Kansas, USA .RE .PP .PP Definition at line 122 of file slaqr1\&.f\&. .SH "Author" .PP Generated automatically by Doxygen for LAPACK from the source code\&.