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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)
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 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.
I
D
Z
DELTA
RHO
DSIGMA
WORK
Author:
I is INTEGER The index of the eigenvalue to be computed. I = 1 or I = 2.
D is DOUBLE PRECISION array, dimension ( 2 ) The original eigenvalues. We assume 0 <= D(1) < D(2).
Z is DOUBLE PRECISION array, dimension ( 2 ) The components of the updating vector.
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 is DOUBLE PRECISION The scalar in the symmetric updating formula.
DSIGMA is DOUBLE PRECISION The computed sigma_I, the I-th updated eigenvalue.
WORK is DOUBLE PRECISION array, dimension ( 2 ) WORK contains (D(j) + sigma_I) in its j-th component.
Univ. of Tennessee
Univ. of California Berkeley
Univ. of Colorado Denver
NAG Ltd.
Date:
November 2011
Contributors:
Ren-Cang Li, Computer Science Division,
University of California at Berkeley, USA
Author¶
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