Subroutine */
| 11112 | } /* dlaed4_ */ |
| 11113 | |
| 11114 | /* Subroutine */ int dlaed5_(integer *i__, doublereal *d__, doublereal *z__, |
| 11115 | doublereal *delta, doublereal *rho, doublereal *dlam) |
| 11116 | { |
| 11117 | /* System generated locals */ |
| 11118 | doublereal d__1; |
| 11119 | |
| 11120 | /* Local variables */ |
| 11121 | static doublereal b, c__, w, del, tau, temp; |
| 11122 | |
| 11123 | |
| 11124 | /* |
| 11125 | -- LAPACK routine (version 3.2) -- |
| 11126 | -- LAPACK is a software package provided by Univ. of Tennessee, -- |
| 11127 | -- Univ. of California Berkeley, Univ. of Colorado Denver and NAG Ltd..-- |
| 11128 | November 2006 |
| 11129 | |
| 11130 | |
| 11131 | Purpose |
| 11132 | ======= |
| 11133 | |
| 11134 | This subroutine computes the I-th eigenvalue of a symmetric rank-one |
| 11135 | modification of a 2-by-2 diagonal matrix |
| 11136 | |
| 11137 | diag( D ) + RHO * Z * transpose(Z) . |
| 11138 | |
| 11139 | The diagonal elements in the array D are assumed to satisfy |
| 11140 | |
| 11141 | D(i) < D(j) for i < j . |
| 11142 | |
| 11143 | We also assume RHO > 0 and that the Euclidean norm of the vector |
| 11144 | Z is one. |
| 11145 | |
| 11146 | Arguments |
| 11147 | ========= |
| 11148 | |
| 11149 | I (input) INTEGER |
| 11150 | The index of the eigenvalue to be computed. I = 1 or I = 2. |
| 11151 | |
| 11152 | D (input) DOUBLE PRECISION array, dimension (2) |
| 11153 | The original eigenvalues. We assume D(1) < D(2). |
| 11154 | |
| 11155 | Z (input) DOUBLE PRECISION array, dimension (2) |
| 11156 | The components of the updating vector. |
| 11157 | |
| 11158 | DELTA (output) DOUBLE PRECISION array, dimension (2) |
| 11159 | The vector DELTA contains the information necessary |
| 11160 | to construct the eigenvectors. |
| 11161 | |
| 11162 | RHO (input) DOUBLE PRECISION |
| 11163 | The scalar in the symmetric updating formula. |
| 11164 | |
| 11165 | DLAM (output) DOUBLE PRECISION |
| 11166 | The computed lambda_I, the I-th updated eigenvalue. |
| 11167 | |
| 11168 | Further Details |
| 11169 | =============== |
| 11170 | |
| 11171 | Based on contributions by |