Developer Reference for Intel® oneAPI Math Kernel Library - C

Developer Reference

Contents

?lasd5

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
?bdsdc
.

Syntax

void slasd5
(
lapack_int
*i
,
float
*d
,
float
*z
,
float
*delta
,
float
*rho
,
float
*dsigma
,
float
*work
);
void dlasd5
(
lapack_int
*i
,
double
*d
,
double
*z
,
double
*delta
,
double
*rho
,
double
*dsigma
,
double
*work
);
Include Files
  • mkl.h
Description
The routine 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
*
Z
T
The diagonal entries in the array
d
 must satisfy
0 ≤
d
(i) <
d
(j)
 for
i<i
,
rho
 mustbe greater than 0, and that the Euclidean norm of the vector
Z
 is equal to 1.
Input Parameters
i
The index of the eigenvalue to be computed.
i
 = 1
 or
i
 = 2
.
d
Array,
dimension
 (2 ).
The original eigenvalues,
0 ≤
d
(1) <
d
(2)
.
z
Array,
dimension
 ( 2 ).
The components of the updating vector.
rho
The scalar in the symmetric updating formula.
work
Workspace array,
dimension
 ( 2 ). Contains (
d
(
j
) +
sigma_i
) in its
j
-th component.
Output Parameters
delta
Array,
dimension
 ( 2 ).
Contains (
d
(
j
) -
sigma_i
) in its
j
-th component. The vector
delta
 contains the information necessary to construct the eigenvectors.
dsigma
The computed
sigma_i
, the
i
-th updated eigenvalue.

Product and Performance Information

1

Performance varies by use, configuration and other factors. Learn more at www.Intel.com/PerformanceIndex.