Developer Reference for Intel® oneAPI Math Kernel Library for Fortran
?laed5
Used by sstedc / dstedc . Solves the 2-by-2 secular equation.
Syntax
call slaed5 ( i , d , z , delta , rho , dlam )
call dlaed5 ( i , d , z , delta , rho , dlam )
Include Files
mkl.fi
Description
slaed5 dlaed5
The routine 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.
Input Parameters
- i
-
INTEGER . The index of the eigenvalue to be computed; 1 ≤ i ≤ 2 .
- d , z
-
REAL for slaed5 DOUBLE PRECISION for dlaed5 Arrays, dimension (2) each. The array d contains the original eigenvalues. It is assumed that d(1) < d(2) . The array z contains the components of the updating vector.
- rho
-
REAL for slaed5 DOUBLE PRECISION for dlaed5 The scalar in the symmetric updating formula.
Output Parameters
- delta
-
REAL for slaed5 DOUBLE PRECISION for dlaed5 Array, dimension (2). The vector delta contains the information necessary to construct the eigenvectors.
- dlam
-
REAL for slaed5 DOUBLE PRECISION for dlaed5 The computed lambda_i , the i -th updated eigenvalue.