Developer Reference for Intel® oneAPI Math Kernel Library - C

Developer Reference

  • 2021.1
  • 12/04/2020
  • Public Content
Contents

?pttrf

Computes the factorization of a symmetric (Hermitian) positive-definite tridiagonal matrix.

Syntax

lapack_int LAPACKE_spttrf
(
lapack_int
n
,
float*
d
,
float*
e
);
lapack_int LAPACKE_dpttrf
(
lapack_int
n
,
double*
d
,
double*
e
);
lapack_int LAPACKE_cpttrf
(
lapack_int
n
,
float*
d
,
lapack_complex_float*
e
);
lapack_int LAPACKE_zpttrf
(
lapack_int
n
,
double*
d
,
lapack_complex_double*
e
);
Include Files
  • mkl.h
Description
The routine forms the factorization of a symmetric positive-definite or, for complex data, Hermitian positive-definite tridiagonal matrix
A
:
A
 =
L*D*L
T
 for real flavors, or
A
 =
L*D*L
H
 for complex flavors,
where
D
 is diagonal and
L
 is unit lower bidiagonal. The factorization may also be regarded as having the form
A
 =
U
T
*D*U
 for real flavors, or
A
 =
U
H
*D*U
 for complex flavors, where
U
 is unit upper bidiagonal.
Input Parameters
n
The order of the matrix
A
;
n
≥
 0.
d
Array, dimension (
n
). Contains the diagonal elements of
A
.
e
Array, dimension (
n
 -1). Contains the subdiagonal elements of
A
.
Output Parameters
d
Overwritten by the
n
 diagonal elements of the diagonal matrix
D
 from the
L*D*L
T
 (for real flavors) or
L*D*L
H
 (for complex flavors) factorization of
A
.
e
Overwritten by the
(
n
 - 1)
 sub-diagonal elements of the unit bidiagonal factor
L
 or
U
 from the factorization of
A
.
Return Values
This function returns a value
info
.
If
info
 = 0
, the execution is successful.
If
info
 =
-i
, parameter
i
 had an illegal value.
If
info
 =
i
, the leading minor of order
i
 (and therefore the matrix
A
 itself) is not positive-definite; if
i
 <
n
, the factorization could not be completed, while if
i
 =
n
, the factorization was completed, but
d
[
n
 - 1] ≤ 0
.

Product and Performance Information

1

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