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| laed5(3) | LAPACK | laed5(3) |
NAME
laed5 - laed5: D&C step: secular equation, 2x2
SYNOPSIS
Functions
subroutine dlaed5 (i, d, z, delta, rho, dlam)
DLAED5 used by DSTEDC. Solves the 2-by-2 secular equation. subroutine
slaed5 (i, d, z, delta, rho, dlam)
SLAED5 used by SSTEDC. Solves the 2-by-2 secular equation.
Detailed Description
Function Documentation
subroutine dlaed5 (integer i, double precision, dimension( 2 ) d, double precision, dimension( 2 ) z, double precision, dimension( 2 ) delta, double precision rho, double precision dlam)
DLAED5 used by DSTEDC. 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 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 California Berkeley
Univ. of Colorado Denver
NAG Ltd.
Contributors:
Definition at line 107 of file dlaed5.f.
subroutine slaed5 (integer i, real, dimension( 2 ) d, real, dimension( 2 ) z, real, dimension( 2 ) delta, real rho, real dlam)
SLAED5 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 is INTEGER
The index of the eigenvalue to be computed. I = 1 or I = 2.
D
D is REAL array, dimension (2)
The original eigenvalues. We assume D(1) < D(2).
Z
Z is REAL array, dimension (2)
The components of the updating vector.
DELTA
DELTA is REAL array, dimension (2)
The vector DELTA contains the information necessary
to construct the eigenvectors.
RHO
RHO is REAL
The scalar in the symmetric updating formula.
DLAM
DLAM is REAL
The computed lambda_I, the I-th updated eigenvalue.
Author
Univ. of California Berkeley
Univ. of Colorado Denver
NAG Ltd.
Contributors:
Definition at line 107 of file slaed5.f.
Author
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| Sun Jan 12 2025 15:13:37 | Version 3.12.1 |
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