Developer Reference

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

?hesv_rk

?hesv_rk
computes the solution to a system of linear equations A * X = B for Hermitian matrices.
lapack_int
LAPACKE_chesv_rk
(
int
matrix_layout
,
char
uplo
,
lapack_int
n
,
lapack_int
nrhs
,
lapack_complex_float
*
A
,
lapack_int
lda
,
lapack_complex_float
*
e
,
lapack_int
*
ipiv
,
lapack_complex_float
*
B
,
lapack_int
ldb
);
lapack_int
LAPACKE_zhesv_rk
(
int
matrix_layout
,
char
uplo
,
lapack_int
n
,
lapack_int
nrhs
,
lapack_complex_double
*
A
,
lapack_int
lda
,
lapack_complex_double
*
e
,
lapack_int
*
ipiv
,
lapack_complex_double
*
B
,
lapack_int
ldb
);
Description
?hesv_rk
computes the solution to a complex system of linear equations A * X = B, where A is an
n
-by-
n
Hermitian matrix and X and B are
n
-by-
nrhs
matrices.
The bounded Bunch-Kaufman (rook) diagonal pivoting method is used to factor A as A = P*U*D*(U
H
)*(P
T
), if
uplo
=
'U'
, or A = P*L*D*(L
H
)*(P
T
), if
uplo
=
'L'
, where U (or L) is unit upper (or lower) triangular matrix, U
H
(or L
H
) is the conjugate of U (or L), P is a permutation matrix, P
T
is the transpose of P, and D is Hermitian and block diagonal with 1-by-1 and 2-by-2 diagonal blocks.
?hetrf_rk
is called to compute the factorization of a complex Hermitian matrix. The factored form of A is then used to solve the system of equations A * X = B by calling BLAS3 routine
?hetrs_3
.
Input Parameters
matrix_layout
Specifies whether matrix storage layout is row major (
LAPACK_ROW_MAJOR
) or column major (
LAPACK_COL_MAJOR
).
uplo
Specifies whether the upper or lower triangular part of the Hermitian matrix A is stored:
  • =
    'U'
    : The upper triangle of A is stored.
  • =
    'L'
    : The lower triangle of A is stored.
n
The number of linear equations; that is, the order of the matrix A.
n
≥ 0.
nrhs
The number of right-hand sides; that is, the number of columns of the matrix B.
nrhs
≥ 0.
A
Array of size max(1,
lda
*
n
).
On entry, the Hermitian matrix A. If
uplo
=
'U'
: the leading
n
-by-
n
upper triangular part of A contains the upper triangular part of the matrix A, and the strictly lower triangular part of A is not referenced. If
uplo
=
'L'
: the leading
n
-by-
n
lower triangular part of A contains the lower triangular part of the matrix A, and the strictly upper triangular part of A is not referenced.
lda
The leading dimension of the array
A
.
B
On entry, the
n
-by-
nrhs
right-hand side matrix B.
The size of
B
is max(1,
ldb
*
nrhs
) for column-major layout and max(1,
ldb
*
n
) for row-major layout.
ldb
The leading dimension of the array
B
.
ldb
≥ max(1,
n
) for column-major layout and
ldb
nrhs
for row-major layout.
Output Parameters
A
On exit, if
info
= 0, diagonal of the block diagonal matrix D and factors U or L as computed by
?hetrf_rk
:
  • Only
    diagonal elements of the Hermitian block diagonal matrix D on the diagonal of A; that is, D(
    k
    ,
    k
    ) =
    A
    (
    k
    ,
    k
    ); (superdiagonal (or subdiagonal) elements of D are stored on exit in array
    e
    ).
    —and—
  • If
    uplo
    =
    'U'
    , factor U in the superdiagonal part of A. If
    uplo
    =
    'L'
    , factor L in the subdiagonal part of A.
For more information, see the description of the
?hetrf_rk
routine.
e
Array of size
n
.
On exit, contains the output computed by the factorization routine
?hetrf_rk
; that is, the superdiagonal (or subdiagonal) elements of the Hermitian block diagonal matrix D with 1-by-1 or 2-by-2 diagonal blocks:
  • If
    uplo
    =
    'U'
    , e(
    i
    ) = D(
    i
    -1,
    i
    ),
    i
    =2:N, e(1) is set to 0.
  • If
    uplo
    =
    'L'
    , e(
    i
    ) = D(
    i
    +1,
    i
    ),
    i
    =1:N-1, e(
    n
    ) is set to 0.
For a 1-by-1 diagonal block D(
k
), where 1 ≤
k
n
, the element e(
k
) is set to 0 in both the
uplo
=
'U'
and
uplo
=
'L'
cases.
For more information, see the description of the
?hetrf_rk
routine.
ipiv
Array of size
n
.
Details of the interchanges and the block structure of D, as determined by
?hetrf_rk
.
B
On exit, if
info
= 0, the
n
-by-
nrhs
solution matrix X.
Return Values
This function returns a value
info
.
= 0: Successful exit.
< 0: If
info
=
-k
, the
k
th
argument had an illegal value.
> 0: If
info
=
k
, the matrix A is singular. If
uplo
=
'U'
, column
k
in the upper triangular part of A contains all zeros. If
uplo
=
'L'
, column
k
in the lower triangular part of A contains all zeros. Therefore D(
k
,
k
) is exactly zero, and superdiagonal elements of column
k
of U (or subdiagonal elements of column
k
of L ) are all zeros. 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.