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dlaed5.f(3) LAPACK dlaed5.f(3)

NAME

dlaed5.f -

SYNOPSIS

Functions/Subroutines


subroutine dlaed5 (I, D, Z, DELTA, RHO, DLAM)
 
DLAED5 used by sstedc. Solves the 2-by-2 secular equation.

Function/Subroutine Documentation

subroutine dlaed5 (integerI, double precision, dimension( 2 )D, double precision, dimension( 2 )Z, double precision, dimension( 2 )DELTA, double precisionRHO, double precisionDLAM)

DLAED5 used by sstedc. Solves the 2-by-2 secular equation.
Purpose: 
 This subroutine computes the I-th eigenvalue of a symmetric rank-one
 modification of a 2-by-2 diagonal matrix


            diag( D )  +  RHO * Z * transpose(Z) .


 The diagonal elements in the array D are assumed to satisfy


            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 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)
         The vector DELTA contains the information necessary
         to construct the eigenvectors.
RHO 
          RHO is DOUBLE PRECISION
         The scalar in the symmetric updating formula.
DLAM 
          DLAM is DOUBLE PRECISION
         The computed lambda_I, the I-th updated eigenvalue.
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 109 of file dlaed5.f.

Author

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