Developer Reference for Intel® oneAPI Math Kernel Library - C

Developer Reference

  • 0.9
  • 09/09/2020
  • 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

Intel's compilers may or may not optimize to the same degree for non-Intel microprocessors for optimizations that are not unique to Intel microprocessors. These optimizations include SSE2, SSE3, and SSSE3 instruction sets and other optimizations. Intel does not guarantee the availability, functionality, or effectiveness of any optimization on microprocessors not manufactured by Intel. Microprocessor-dependent optimizations in this product are intended for use with Intel microprocessors. Certain optimizations not specific to Intel microarchitecture are reserved for Intel microprocessors. Please refer to the applicable product User and Reference Guides for more information regarding the specific instruction sets covered by this notice.

Notice revision #20110804