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CentOS 7.0 - man page for dlasd5 (centos section 3)

dlasd5.f(3)							      LAPACK							       dlasd5.f(3)

NAME
dlasd5.f -
SYNOPSIS
Functions/Subroutines subroutine dlasd5 (I, D, Z, DELTA, RHO, DSIGMA, WORK) DLASD5 computes the square root of the i-th eigenvalue of a positive symmetric rank-one modification of a 2-by-2 diagonal matrix. Used by sbdsdc. Function/Subroutine Documentation subroutine dlasd5 (integerI, double precision, dimension( 2 )D, double precision, dimension( 2 )Z, double precision, dimension( 2 )DELTA, double precisionRHO, double precisionDSIGMA, double precision, dimension( 2 )WORK) DLASD5 computes the square root of the i-th eigenvalue of a positive symmetric rank-one modification of a 2-by-2 diagonal matrix. Used by sbdsdc. Purpose: This subroutine computes the square root of the I-th eigenvalue of a positive symmetric rank-one modification of a 2-by-2 diagonal matrix diag( D ) * diag( D ) + RHO * Z * transpose(Z) . The diagonal entries in the array D are assumed to satisfy 0 <= D(i) < D(j) for i < j . We also assume RHO > 0 and that the Euclidean norm of the vector Z is one. Parameters: I I is INTEGER The index of the eigenvalue to be computed. I = 1 or I = 2. D D is DOUBLE PRECISION array, dimension ( 2 ) The original eigenvalues. We assume 0 <= D(1) < D(2). Z Z is DOUBLE PRECISION array, dimension ( 2 ) The components of the updating vector. DELTA DELTA is DOUBLE PRECISION array, dimension ( 2 ) Contains (D(j) - sigma_I) in its j-th component. The vector DELTA contains the information necessary to construct the eigenvectors. RHO RHO is DOUBLE PRECISION The scalar in the symmetric updating formula. DSIGMA DSIGMA is DOUBLE PRECISION The computed sigma_I, the I-th updated eigenvalue. WORK WORK is DOUBLE PRECISION array, dimension ( 2 ) WORK contains (D(j) + sigma_I) in its j-th component. Author: Univ. of Tennessee Univ. of California Berkeley Univ. of Colorado Denver NAG Ltd. Date: September 2012 Contributors: Ren-Cang Li, Computer Science Division, University of California at Berkeley, USA Definition at line 117 of file dlasd5.f. Author Generated automatically by Doxygen for LAPACK from the source code. Version 3.4.2 Tue Sep 25 2012 dlasd5.f(3)