Developer Reference for Intel® oneAPI Math Kernel Library - C

Developer Reference

Contents

cblas_?syr2

Performs
 a rank-2 update of a symmetric matrix.

Syntax

void
cblas_ssyr2
(
const
CBLAS_LAYOUT
Layout
,
const
CBLAS_UPLO
uplo
,
const
MKL_INT
n
,
const
float
alpha
,
const
float
*x
,
const
MKL_INT
incx
,
const
float
*y
,
const
MKL_INT
incy
,
float
*a
,
const
MKL_INT
lda
);
void
cblas_dsyr2
(
const
CBLAS_LAYOUT
Layout
,
const
CBLAS_UPLO
uplo
,
const
MKL_INT
n
,
const
double
alpha
,
const
double
*x
,
const
MKL_INT
incx
,
const
double
*y
,
const
MKL_INT
incy
,
double
*a
,
const
MKL_INT
lda
);
Include Files
  • mkl.h
Description
The
?syr2
 routines perform a matrix-vector operation defined as 
A := alpha*x*y'+ alpha*y*x' + A,
where:
alpha
 is scalar,
x
 and
y
 are
n
-element vectors,
A
 is an
n
-by-
n
 symmetric matrix.
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
a
 is used.
If
uplo
 =
CblasUpper
, then the upper triangular part of the array
a
 is used.
If
uplo
 =
CblasLower
, then the low triangular part of the array
a
 is used.
n
Specifies the order of the matrix
A
. The value of
n
 must be at least zero.
alpha
Specifies the scalar
alpha
.
x
Array, size at least
(1 + (
n
 - 1)*abs(
incx
))
. Before entry, the incremented array
x
 must contain the
n
-element vector
x
.
incx
Specifies the increment for the elements of
x
.
The value of
incx
 must not be zero.
y
Array, size at least
(1 + (
n
 - 1)*abs(
incy
))
. Before entry, the incremented array
y
 must contain the
n
-element vector
y
.
incy
Specifies the increment for the elements of
y
. The value of
incy
 must not be zero.
a
Array, size
lda
*
n
.
Before entry with
uplo
 =
CblasUpper
, the leading
n
-by-
n
 upper triangular part of the array
a
 must contain the upper triangular part of the symmetric matrix and the strictly lower triangular part of
a
 is not referenced.
Before entry with
uplo
 =
CblasLower
, the leading
n
-by-
n
 lower triangular part of the array
a
 must contain the lower triangular part of the symmetric matrix and the strictly upper triangular part of
a
 is not referenced.
lda
Specifies the leading dimension of
a
 as declared in the calling (sub)program. The value of
lda
 must be at least
max(1,
n
)
.
Output Parameters
a
With
uplo
 =
CblasUpper
, the upper triangular part of the array
a
 is overwritten by the upper triangular part of the updated matrix.
With
uplo
 =
CblasLower
, the lower triangular part of the array
a
 is overwritten by the lower triangular part of the updated matrix.

Product and Performance Information

1

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