# gemv¶

Computes a sparse matrix-dense vector product.

Description and Assumptions

Refer to Supported Types for a list of supported <fp> and <intType>. The oneapi::mkl::sparse::gemv routine computes a sparse matrix-dense vector product defined as

$y \leftarrow \alpha \text{op}(A) x + \beta y$

where $$\alpha$$ and $$\beta$$ are scalars, $$x$$ and $$y$$ are dense vectors, A is a sparse matrix.

## gemv (Buffer version)¶

Syntax

namespace oneapi::mkl::sparse {

void gemv (sycl::queue                          &queue,
oneapi::mkl::transpose               transpose_val,
const fp                             alpha,
oneapi::mkl::sparse::matrix_handle_t A_handle,
sycl::buffer<fp, 1>                  &x,
const fp                             beta,
sycl::buffer<fp, 1>                  &y);

}


Input Parameters

queue

Specifies the SYCL command queue which will be used for SYCL kernels execution.

transpose_val

Specifies operation op() on input matrix. The possible options are described in transpose enum class.

alpha

Specifies the scalar $$\alpha$$.

A_handle

Handle to object containing sparse matrix, $$A$$. Created using the oneapi::mkl::sparse::set_csr_data routine.

x

SYCL memory object containing an array of size at least equal to the number of columns of matrix $$\text{op}(A)$$.

beta

Specifies the scalar $$\beta$$.

y

SYCL memory object containing an array of size at least equal to the number of rows of matrix $$\text{op}(A)$$.

Output Parameters

y

Overwritten by the updated vector y.

Throws

This routine shall throw the following exceptions if the associated condition is detected. An implementation may throw additional implementation-specific exception(s) in case of error conditions not covered here.

## gemv (USM version)¶

Syntax

namespace oneapi::mkl::sparse {

sycl::event gemv (sycl::queue                           &queue,
oneapi::mkl::transpose                transpose_val,
const fp                              alpha,
oneapi::mkl::sparse::matrix_handle_t  A_handle,
const fp                              *x,
const fp                              beta,
const fp                              *y,
const std::vector<sycl::event>        &dependencies = {});

}


Input Parameters

queue

Specifies the SYCL command queue which will be used for SYCL kernels execution.

transpose_val

Specifies operation op() on input matrix. The possible options are described in transpose enum class.

alpha

Specifies the scalar $$\alpha$$.

A_handle

Handle to object containing sparse matrix, $$A$$. Created using the oneapi::mkl::sparse::set_csr_data routine.

x

Device-accessible USM object containing an array of size at least equal to the number of columns of matrix $$\text{op}(A)$$.

beta

Specifies the scalar $$\beta$$.

y

Device-accessible USM object containing an array of size at least equal to the number of rows of matrix $$\text{op}(A)$$.

dependencies

List of events that oneapi::mkl::sparse::gemv routine depends on. If omitted, defaults to no dependencies.

Output Parameters

y

Overwritten by the updated vector y.

Throws

This routine shall throw the following exceptions if the associated condition is detected. An implementation may throw additional implementation-specific exception(s) in case of error conditions not covered here.

Return Values

Output event that can be waited upon or added as a dependency for the completion of gemv routine.