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CentOS 7.0 - man page for slasd5 (centos section 3)

slasd5.f(3)							      LAPACK							       slasd5.f(3)

NAME
slasd5.f -
SYNOPSIS
Functions/Subroutines subroutine slasd5 (I, D, Z, DELTA, RHO, DSIGMA, WORK) SLASD5 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 slasd5 (integerI, real, dimension( 2 )D, real, dimension( 2 )Z, real, dimension( 2 )DELTA, realRHO, realDSIGMA, real, dimension( 2 )WORK) SLASD5 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 REAL array, dimension (2) The original eigenvalues. We assume 0 <= D(1) < D(2). Z Z is REAL array, dimension (2) The components of the updating vector. DELTA DELTA is REAL 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 REAL The scalar in the symmetric updating formula. DSIGMA DSIGMA is REAL The computed sigma_I, the I-th updated eigenvalue. WORK WORK is REAL 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 slasd5.f. Author Generated automatically by Doxygen for LAPACK from the source code. Version 3.4.2 Tue Sep 25 2012 slasd5.f(3)