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template<typename T>
void laed5(integer *i, T *d, T *z, T *delta, T *rho, T *dlam)# LAED5 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 – [in]
I is INTEGER
The index of the eigenvalue to be computed. I = 1 or I = 2.
D – [in]
D is REAL array, dimension (2)
The original eigenvalues. We assume D(1) < D(2).
Z – [in]
Z is REAL array, dimension (2)
The components of the updating vector.
DELTA – [out]
DELTA is REAL array, dimension (2)
The vector DELTA contains the information necessary to construct the eigenvectors.
RHO – [in]
RHO is REAL
The scalar in the symmetric updating formula.
DLAM – [out]
DLAM is REAL
The computed lambda_I, the I-th updated eigenvalue.