.. _onemkl_blas_asum:

asum
====

Computes the sum of magnitudes of the vector elements.

Description
***********

The ``asum`` routine computes the sum of the magnitudes of elements of a
real vector, or the sum of magnitudes of the real and imaginary parts
of elements of a complex vector. The operation is defined as: 

.. math::

      \mathrm{result} \leftarrow \sum_{i=1}^n
      \left( |\mathrm{Re} (X_i)| + |\mathrm{Im}(X_i)| \right)

where:

- ``x`` is a vector with ``n`` elements

``asum`` supports the following precisions:

.. list-table::
      :header-rows: 1

      * -  T
        -  T_res
      * -  ``float``
        -  ``float``
      * -  ``double``
        -  ``double``
      * -  ``std::complex<float>``
        -  ``float``
      * -  ``std::complex<double>``
        -  ``double``


asum (Buffer Version)
*********************

Syntax
------

.. code-block:: cpp

   namespace oneapi::mkl::blas::column_major {
       void asum(sycl::queue &queue,
                 std::int64_t n,
                 sycl::buffer<T,1> &x,
                 std::int64_t incx,
                 sycl::buffer<T_res,1> &result)
   }

.. code-block:: cpp

   namespace oneapi::mkl::blas::row_major {
       void asum(sycl::queue &queue,
                 std::int64_t n,
                 sycl::buffer<T,1> &x,
                 std::int64_t incx,
                 sycl::buffer<T_res,1> &result)
   }

Input Parameters
----------------

queue
   The queue where the routine should be executed.

n
   Number of elements in vector ``x``.

x
   Buffer holding input vector ``x``. Size of the buffer must be at 
   least (1 + (``n`` - 1)*abs(``incx``)). See :ref:`matrix-storage` for
   more details.

incx
   Stride of vector ``x``.

Output Parameters
-----------------

result
   Buffer where the scalar result is stored. 


asum (USM Version)
******************

Syntax
------

.. code-block:: cpp

   namespace oneapi::mkl::blas::column_major {
       sycl::event asum(sycl::queue &queue,
                        std::int64_t n,
                        const T *x,
                        std::int64_t incx,
                        T_res *result,
                        const std::vector<sycl::event> &dependencies = {})
   }

.. code-block:: cpp

   namespace oneapi::mkl::blas::row_major {
       sycl::event asum(sycl::queue &queue,
                        std::int64_t n,
                        const T *x,
                        std::int64_t incx,
                        T_res *result,
                        const std::vector<sycl::event> &dependencies = {})
   }

Input Parameters
----------------

queue
   The queue where the routine should be executed.

n
   Number of elements in vector ``x``.

x
   Pointer to input vector ``x``. Size of the array holding vector ``x``
   must be least (1 + (``n`` - 1)\*abs(``incx``)). See
   :ref:`matrix-storage` for more details.

incx
   Stride of vector ``x``.

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

Output Parameters
-----------------

result
   Pointer to where the scalar result is stored.
   
Return Values
-------------

Output event to wait on to ensure computation is complete.