# spr2¶

Computes a rank-2 update of a symmetric packed matrix.

Description

The spr2 routines compute two scalar-vector-vector products and add them to a symmetric packed matrix. The operation is defined as:

$A \leftarrow alpha*x*y^T + alpha*y*x^T + A$

where:

alpha is scalar,

A is an n-by-n symmetric matrix, supplied in packed form,

x and y are vectors of length n.

spr supports the following precisions.

T

float

double

## spr2 (Buffer Version)¶

Syntax

namespace oneapi::mkl::blas::column_major {
void spr2(sycl::queue &queue,
onemkl::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)
}

namespace oneapi::mkl::blas::row_major {
void spr2(sycl::queue &queue,
onemkl::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)
}


Input Parameters

queue

The queue where the routine should be executed.

upper_lower

Specifies whether A is upper or lower triangular. See oneMKL defined datatypes for more details.

n

Number of rows and columns of A. Must be at least zero.

alpha

Scaling factor for the matrix-vector product.

x

Buffer holding input vector x. The buffer must be of size 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. The buffer must be of size at least (1 + (n - 1)*abs(incy)). See Matrix Storage for more details.

incy

Stride of vector y.

a

Buffer holding input matrix A. Must have size at least (n*(n-1))/2. See Matrix Storage for more details.

Output Parameters

a

Buffer holding the updated upper triangular part of the symmetric matrix A if upper_lower=upper or the updated lower triangular part of the symmetric matrix A if upper_lower=lower.

## spr2 (USM Version)¶

Syntax

namespace oneapi::mkl::blas::column_major {
sycl::event spr2(sycl::queue &queue,
onemkl::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)
}

namespace oneapi::mkl::blas::row_major {
sycl::event spr2(sycl::queue &queue,
onemkl::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)
}


Input Parameters

queue

The queue where the routine should be executed.

upper_lower

Specifies whether A is upper or lower triangular. See oneMKL defined datatypes for more details.

n

Number of rows and columns of A. Must be at least zero.

alpha

Scaling factor for the matrix-vector product.

x

Pointer to input vector x. The array holding input vector x must be of size 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. The array holding input/output vector y must be of size at least (1 + (n - 1)*abs(incy)). See Matrix Storage for more details.

incy

Stride of vector y.

a

Pointer to input matrix A. The array holding input matrix A must have size at least (n*(n-1))/2. See Matrix Storage for more details.

dependencies

List of events to wait for before starting computation, if any. If omitted, defaults to no dependencies.

Output Parameters

a

Pointer to the updated upper triangular part of the symmetric matrix A if upper_lower=upper or the updated lower triangular part of the symmetric matrix A if upper_lower=lower.

Return Values

Output event to wait on to ensure computation is complete.

Parent topic: BLAS Level 2 Routines