Contents

# her2

Computes a rank-2 update of a hermitian matrix.

## Description

The
her2
routines compute two scalar-vector-vector products and add them to a hermitian matrix. The operation is defined as:
where:
• alpha
is a scalar
• A
is
n
x
n
hermitian matrix
• x
and
y
are vectors or length
n
her2
supports the following precisions:
T
std::complex<float>
std::complex<double>

## her2 (Buffer Version)

Syntax
``````namespace oneapi::mkl::blas::column_major {
void her2(sycl::queue &queue,
oneapi::mkl::uplo upper_lower,
std::int64_t n,
T alpha,
sycl::buffer<T,1> &x,
std::int64_t incx,
sycl::buffer<T,1> &y,
std::int64_t incy,
sycl::buffer<T,1> &a,
std::int64_t lda)
}``````
``````namespace oneapi::mkl::blas::row_major {
void her2(sycl::queue &queue,
oneapi::mkl::uplo upper_lower,
std::int64_t n,
T alpha,
sycl::buffer<T,1> &x,
std::int64_t incx,
sycl::buffer<T,1> &y,
std::int64_t incy,
sycl::buffer<T,1> &a,
std::int64_t lda)
}``````
Input Parameters
queue
The queue where the routine should be executed.
upper_lower
Specifies whether matrix
A
is upper or lower triangular. See Data Types for more details.
n
Number of columns of matrix
A
. Must be at least zero.
alpha
Scaling factor for the matrix-vector product.
x
Buffer holding input vector
x
. Size of the buffer must be at least (1 + (
n
- 1)*abs(
incx
)). See Matrix Storage for more details.
incx
Stride of vector
x
.
y
Buffer holding input/output vector
y
. Size of the buffer must be at least (1 + (
n
- 1)*abs(
incy
)). See Matrix Storage for more details.
incy
Stride of vector
y
.
a
Buffer holding input matrix
A
. Size of the buffer must be at least
lda
*
n
. See Matrix Storage for more details.
lda
Leading dimension of matrix
A
. Must be at least
n
and positive.
Output Parameters
a
Buffer holding updated upper triangular part of the hermitian matrix
A
if
upper_lower=upper
, or updated lower triangular part of the hermitian matrix
A
if
upper_lower=lower
.
The imaginary parts of the diagonal elements are set to zero.

## her2 (USM Version)

Syntax
``````namespace oneapi::mkl::blas::column_major {
sycl::event her2(sycl::queue &queue,
oneapi::mkl::uplo upper_lower,
std::int64_t n,
T alpha,
const T *x,
std::int64_t incx,
const T *y,
std::int64_t incy,
T *a,
std::int64_t lda,
const std::vector<sycl::event> &dependencies = {})
}``````
``````namespace oneapi::mkl::blas::row_major {
sycl::event her2(sycl::queue &queue,
oneapi::mkl::uplo upper_lower,
std::int64_t n,
T alpha,
const T *x,
std::int64_t incx,
const T *y,
std::int64_t incy,
T *a,
std::int64_t lda,
const std::vector<sycl::event> &dependencies = {})
}``````
Input Parameters
queue
The queue where the routine should be executed.
upper_lower
Specifies whether matrix
A
is upper or lower triangular. See Data Types for more details.
n
Number of columns of matrix
A
. Must be at least zero.
alpha
Scaling factor for the matrix-vector product.
x
Pointer to input vector
x
. Size of the array holding input vector
x
must be at least (1 + (
n
- 1)*abs(
incx
)). See Matrix Storage for more details.
incx
Stride of vector
x
.
y
Pointer to input/output vector
y
. Size of the array holding input/output vector
y
must be at least (1 + (
n
- 1)*abs(
incy
)). See Matrix Storage for more details.
incy
Stride of vector
y
.
a
Pointer to input matrix
A
. Size of the array holding input matrix
A
must be at least
lda
*
n
. See Matrix Storage for more details.
lda
Leading dimension of matrix
A
. Must be at least
n
and positive.
dependencies
List of events to wait for before starting computation, if any. If omitted, defaults to no dependencies.
Output Parameters
a
Pointer to updated upper triangular part of the hermitian matrix
A
if
upper_lower=upper
, or updated lower triangular part of the hermitian matrix
A
if
upper_lower=lower
.
The imaginary parts of the diagonal elements are set to zero.
Return Values
Output event to wait on to ensure computation is complete.

#### Product and Performance Information

1

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