1DLAED5(1)                LAPACK routine (version 3.1)                DLAED5(1)
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NAME

6       DLAED5  - compute the I-th eigenvalue of a symmetric rank-one modifica‐
7       tion of a 2-by-2 diagonal matrix   diag( D ) + RHO  The  diagonal  ele‐
8       ments in the array D are assumed to satisfy   D(i) < D(j) for i < j
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SYNOPSIS

11       SUBROUTINE DLAED5( I, D, Z, DELTA, RHO, DLAM )
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13           INTEGER        I
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15           DOUBLE         PRECISION DLAM, RHO
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17           DOUBLE         PRECISION D( 2 ), DELTA( 2 ), Z( 2 )
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PURPOSE

20       This  subroutine  computes  the I-th eigenvalue of a symmetric rank-one
21       modification of a 2-by-2 diagonal matrix
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23       We also assume RHO > 0 and that the Euclidean norm of the vector  Z  is
24       one.
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ARGUMENTS

28       I      (input) INTEGER
29              The index of the eigenvalue to be computed.  I = 1 or I = 2.
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31       D      (input) DOUBLE PRECISION array, dimension (2)
32              The original eigenvalues.  We assume D(1) < D(2).
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34       Z      (input) DOUBLE PRECISION array, dimension (2)
35              The components of the updating vector.
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37       DELTA  (output) DOUBLE PRECISION array, dimension (2)
38              The vector DELTA contains the information necessary to construct
39              the eigenvectors.
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41       RHO    (input) DOUBLE PRECISION
42              The scalar in the symmetric updating formula.
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44       DLAM   (output) DOUBLE PRECISION
45              The computed lambda_I, the I-th updated eigenvalue.
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FURTHER DETAILS

48       Based on contributions by
49          Ren-Cang Li, Computer Science Division, University of California
50          at Berkeley, USA
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55 LAPACK routine (version 3.1)    November 2006                       DLAED5(1)