Developer Reference for Intel® oneAPI Math Kernel Library - C

Developer Reference

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?sytrf_aa

Computes the factorization of a symmetric matrix using Aasen's algorithm.
lapack_int
LAPACKE_ssytrf_aa
(
int
matrix_layout
,
char
uplo
,
lapack_int
n
,
float
*
A
,
lapack_int
lda
,
lapack_int
*
ipiv
);
lapack_int
LAPACKE_dsytrf_aa
(
int
matrix_layout
,
char
uplo
,
lapack_int
n
,
double
*
A
,
lapack_int
lda
,
lapack_int
*
ipiv
);
lapack_int
LAPACKE_csytrf_aa
(
int
matrix_layout
,
char
uplo
,
lapack_int
n
,
lapack_complex_float
*
A
,
lapack_int
lda
,
lapack_int
*
ipiv
);
lapack_int
LAPACKE_zsytrf_aa
(
int
matrix_layout
,
char
uplo
,
lapack_int
n
,
lapack_complex_double
*
A
,
lapack_int
lda
,
lapack_int
*
ipiv
);
Description
?sytrf_aa
 computes the factorization of a symmetric matrix A using Aasen's algorithm. The form of the factorization is A = U*T*U
T
 or A = L*T*L
T
 where U (or L) is a product of permutation and unit upper (lower) triangular matrices, and T is a complex symmetric tridiagonal matrix.
This is the blocked version of the algorithm, calling Level 3 BLAS.
Input Parameters
matrix_layout
Specifies whether matrix storage layout is row major (
LAPACK_ROW_MAJOR
) or column major (
LAPACK_COL_MAJOR
).
uplo
  • =
    'U'
    : The upper triangle of A is stored.
  • =
    'L'
    : The lower triangle of A is stored.
n
The order of the matrix A.
n
 ≥ 0.
A
Array of size max(1,
lda
*
n
). The array
A
 contains either the upper or the lower triangular part of the matrix A (see
uplo
).
lda
The leading dimension of the array
A
.
Output Parameters
A
On exit, the tridiagonal matrix is stored in the diagonals and the subdiagonals of A just below (or above) the diagonals, and L is stored below (or above) the subdiagonals, when
uplo
 is
'L'
 (or
'U'
).
ipiv
Array of size
n
.
 On exit, it contains the details of the interchanges; that is, the row and column
k
 of A were interchanged with the row and column
ipiv
(
k
)
.
Return Values
This function returns a value
info
.
= 0: Successful exit.
< 0: If
info
 =
-i
, the
i
th
 argument had an illegal value.
> 0: If
info
 =
i
, D(
i
,
i
) is exactly zero. The factorization has been completed, but the block diagonal matrix D is exactly singular, and division by zero will occur if it is used to solve a system of equations.

Product and Performance Information

1

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