Developer Reference for Intel® oneAPI Math Kernel Library - C

Developer Reference

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

cblas_?herk

Performs a Hermitian rank-k update.

Syntax

void
cblas_cherk
(
const
CBLAS_LAYOUT
Layout
,
const
CBLAS_UPLO
uplo
,
const
CBLAS_TRANSPOSE
trans
,
const
MKL_INT
n
,
const
MKL_INT
k
,
const
float
alpha
,
const
void
*a
,
const
MKL_INT
lda
,
const
float
beta
,
void
*c
,
const
MKL_INT
ldc
);
void
cblas_zherk
(
const
CBLAS_LAYOUT
Layout
,
const
CBLAS_UPLO
uplo
,
const
CBLAS_TRANSPOSE
trans
,
const
MKL_INT
n
,
const
MKL_INT
k
,
const
double
alpha
,
const
void
*a
,
const
MKL_INT
lda
,
const
double
beta
,
void
*c
,
const
MKL_INT
ldc
);
Include Files
  • mkl.h
Description
The
?herk
routines perform a rank-k matrix-matrix operation using a general matrix
A
 and a Hermitian matrix
C
.
 The operation is defined as:
C := alpha*A*A
H
 + beta*C,
or 
C := alpha*A
H
*A + beta*C,
where:
alpha
 and
beta
 are real scalars,
C
 is an
n
-by-
n
 Hermitian matrix,
A
 is an
n
-by-
k
 matrix in the first case and a
k
-by-
n
 matrix in the second case.
Input Parameters
Layout
Specifies whether two-dimensional array storage is row-major (
CblasRowMajor
) or column-major (
CblasColMajor
).
uplo
Specifies whether the upper or lower triangular part of the array
c
 is used.
If
uplo
 =
CblasUpper
, then the upper triangular part of the array
c
 is used.
If
uplo
 =
CblasLower
, then the low triangular part of the array
c
 is used.
trans
Specifies the operation:
if
trans
=
CblasNoTrans
, then
C
 :=
alpha
*
A
*
A
H
 +
beta
*
C
;
if
trans
=
CblasConjTrans
, then
C
 :=
alpha
*
A
H
*
A
 +
beta
*
C
.
n
Specifies the order of the matrix
C
.
 The value of
n
 must be at least zero.
k
With
trans
=
CblasNoTrans
,
k
 specifies the number of columns of the matrix
A
, and with
trans
=
CblasConjTrans
,
k
 specifies the number of rows of the matrix
A
.
The value of
k
 must be at least zero.
alpha
Specifies the scalar
alpha
.
a
trans
=
CblasNoTrans
trans
=
CblasConjTrans
Layout
 =
CblasColMajor
Array, size
lda
*
k
.
Before entry, the leading
n
-by-
k
 part of the array
a
 must contain the matrix
A
.
Array, size
lda
*
n
.
Before entry, the leading
k
-by-
n
 part of the array
a
 must contain the matrix
A
.
Layout
 =
CblasRowMajor
Array, size
lda
*
n
.
Before entry, the leading
k
-by-
n
 part of the array
a
 must contain the matrix
A
.
Array, size
lda
*
k
.
Before entry, the leading
n
-by-
k
 part of the array
a
 must contain the matrix
A
.
lda
trans
=
CblasNoTrans
trans
=
CblasConjTrans
Layout
 =
CblasColMajor
lda
 must be at least
max(1,
n
)
.
lda
 must be at least
max(1,
k
)
Layout
 =
CblasRowMajor
lda
 must be at least
max(1,
k
)
lda
 must be at least
max(1,
n
)
.
beta
Specifies the scalar
beta
.
c
Array, size
ldc
 by
n
.
Before entry with
uplo
 =
CblasUpper
, the leading
n
-by-
n
 upper triangular part of the array
c
 must contain the upper triangular part of the Hermitian matrix and the strictly lower triangular part of
c
 is not referenced.
Before entry with
uplo
 =
CblasLower
, the leading
n
-by-
n
 lower triangular part of the array
c
 must contain the lower triangular part of the Hermitian matrix and the strictly upper triangular part of
c
 is not referenced.
The imaginary parts of the diagonal elements need not be set, they are assumed to be zero.
ldc
Specifies the leading dimension of
c
 as declared in the calling (sub)program. The value of
ldc
 must be at least
max(1,
n
)
.
Output Parameters
c
With
uplo
 =
CblasUpper
, the upper triangular part of the array
c
 is overwritten by the upper triangular part of the updated matrix.
With
uplo
 =
CblasLower
, the lower triangular part of the array
c
 is overwritten by the lower triangular part of the updated matrix.
The imaginary parts of the diagonal elements are set to zero.

Product and Performance Information

1

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