?sytrf_aa
?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*UT
or A = L*T*LT
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 arrayAcontains either the upper or the lower triangular part of the matrix A (seeuplo).
- lda
- The leading dimension of the arrayA.
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, whenuplois'L'(or'U').
- ipiv
- Array of sizeOn exit, it contains the details of the interchanges; that is, the row and columnn.kof A were interchanged with the row and columnipiv(.k)
Return Values
This function returns a value
info
.= 0: Successful exit.
< 0: If , the
info
= -i
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.