# gemv¶

Computes a matrix-vector product using a general matrix.

Description

The gemv routines compute a scalar-matrix-vector product and add the result to a scalar-vector product, with a general matrix. The operation is defined as:

$y \leftarrow alpha*op(A)*x + beta*y$

where:

op(A) is one of op(A) = A, or op(A) = AT, or op(A) = AH,

alpha and beta are scalars,

A is an m-by-n matrix, and x, y are vectors.

gemv supports the following precisions.

T

float

double

std::complex<float>

std::complex<double>

## gemv (Buffer Version)¶

Syntax

namespace oneapi::mkl::blas::column_major {
void gemv(sycl::queue &queue,
onemkl::transpose trans,
std::int64_t m,
std::int64_t n,
T alpha,
sycl::buffer<T,1> &a,
std::int64_t lda,
sycl::buffer<T,1> &x,
std::int64_t incx,
T beta,
sycl::buffer<T,1> &y,
std::int64_t incy)
}

namespace oneapi::mkl::blas::row_major {
void gemv(sycl::queue &queue,
onemkl::transpose trans,
std::int64_t m,
std::int64_t n,
T alpha,
sycl::buffer<T,1> &a,
std::int64_t lda,
sycl::buffer<T,1> &x,
std::int64_t incx,
T beta,
sycl::buffer<T,1> &y,
std::int64_t incy)
}


Input Parameters

queue

The queue where the routine should be executed.

trans

Specifies op(A), the transposition operation applied to A.

m

Specifies the number of rows of the matrix A. The value of m must be at least zero.

n

Specifies the number of columns of the matrix A. The value of n must be at least zero.

alpha

Scaling factor for the matrix-vector product.

a

The buffer holding the input matrix A. Must have a size of at least lda*n if column major layout is used or at least lda*m if row major layout is used. See Matrix Storage for more details.

lda

Leading dimension of matrix A. Must be positive and at least m if column major layout is used or at least n if row major layout is used.

x

Buffer holding input vector x. The length len of vector x is n if A is not transposed, and m if A is transposed. The buffer must be of size at least (1 + (len - 1)*abs(incx)). See Matrix Storage for more details.

incx

The stride of vector x.

beta

The scaling factor for vector y.

y

Buffer holding input/output vector y. The length len of vector y is m, if A is not transposed, and n if A is transposed. The buffer must be of size at least (1 + (len - 1)*abs(incy)) where len is this length. See Matrix Storage for more details.

incy

The stride of vector y.

Output Parameters

y

The buffer holding updated vector y.

## gemv (USM Version)¶

Syntax

namespace oneapi::mkl::blas::column_major {
sycl::event gemv(sycl::queue &queue,
onemkl::transpose trans,
std::int64_t m,
std::int64_t n,
T alpha,
const T *a,
std::int64_t lda,
const T *x,
std::int64_t incx,
T beta,
T *y,
std::int64_t incy,
const std::vector<sycl::event> &dependencies = {})
}

namespace oneapi::mkl::blas::row_major {
sycl::event gemv(sycl::queue &queue,
onemkl::transpose trans,
std::int64_t m,
std::int64_t n,
T alpha,
const T *a,
std::int64_t lda,
const T *x,
std::int64_t incx,
T beta,
T *y,
std::int64_t incy,
const std::vector<sycl::event> &dependencies = {})
}


Input Parameters

queue

The queue where the routine should be executed.

trans

Specifies op(A), the transposition operation applied to A. See oneMKL Defined Datatypes for more details.

m

Specifies the number of rows of the matrix A. The value of m must be at least zero.

n

Specifies the number of columns of the matrix A. The value of n must be at least zero.

alpha

Scaling factor for the matrix-vector product.

a

Pointer to the input matrix A. Must have a size of at least lda*n if column major layout is used or at least lda*m if row major layout is used. See Matrix Storage for more details.

lda

Leading dimension of matrix A. Must be positive and at least m if column major layout is used or at least n if row major layout is used.

x

Pointer to the input vector x. The length len of vector x is n if A is not transposed, and m if A is transposed. The array holding vector x must be of size at least (1 + (len - 1)*abs(incx)). See Matrix Storage for more details.

incx

The stride of vector x.

beta

The scaling factor for vector y.

y

Pointer to input/output vector y. The length len of vector y is m, if A is not transposed, and n if A is transposed. The array holding input/output vector y must be of size at least (1 + (len - 1)*abs(incy)) where len is this length. See Matrix Storage for more details.

incy

The stride of vector y.

dependencies

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

Output Parameters

y

The pointer to updated vector y.

Return Values

Output event to wait on to ensure computation is complete.

Parent topic: BLAS Level 2 Routines