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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)
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