.. SPDX-FileCopyrightText: 2019-2020 Intel Corporation
..
.. SPDX-License-Identifier: CC-BY-4.0

.. _onemath_vm_lgamma:

lgamma
======


.. container::


   Computes the natural logarithm of the absolute value of gamma
   function for vector elements.


   .. container:: section


      .. rubric:: Syntax
         :class: sectiontitle


      Buffer API:


      .. code-block:: cpp


            namespace oneapi::math::vm {

            sycl::event lgamma(
                    sycl::queue& exec_queue,
                    std::int64_t n,
                    sycl::buffer<T,1>& a,
                    sycl::buffer<T,1>& y,
                    oneapi::math::vm::mode mode = oneapi::math::vm::mode::not_defined,
                    oneapi::math::vm::error_handler<T> errhandler = {});

            } // namespace oneapi::math::vm



      USM API:


      .. code-block:: cpp


            namespace oneapi::math::vm {

            sycl::event lgamma(
                    sycl::queue& exec_queue,
                    std::int64_t n,
                    const T *a,
                    T* y,
                    std::vector<sycl::event> const & depends = {},
                    oneapi::math::vm::mode mode = oneapi::math::vm::mode::not_defined,
                    oneapi::math::vm::error_handler<T> errhandler = {});

            } // namespace oneapi::math::vm



      ``lgamma`` supports the following precisions.


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

         * - T
         * - ``float``
         * - ``double``




.. container:: section


   .. rubric:: Description
      :class: sectiontitle


   The lgamma(a) function computes the natural logarithm of the absolute
   value of gamma function for elements of the input vector ``a`` and
   writes them to the output vector ``y``. Precision overflow thresholds
   for the lgamma function are beyond the scope of this document. If the
   result does not meet the target precision, the function sets the VM
   status code to ``oneapi::math::vm::status::overflow``.


   .. container:: tablenoborder


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

         * - Argument
           - Result
           - VM status code
         * - +1
           - +0
           -  
         * - +2
           - +0
           -  
         * - +0
           - +∞
           - ``oneapi::math::vm::status::sing``
         * - -0
           - +∞
           - ``oneapi::math::vm::status::sing``
         * - negative integer
           - +∞
           - ``oneapi::math::vm::status::sing``
         * - -∞
           - +∞
           -  
         * - +∞
           - +∞
           -  
         * - a > overflow
           - +∞
           - ``oneapi::math::vm::status::overflow``
         * - QNAN
           - QNAN
           -  
         * - SNAN
           - QNAN
           -  




.. container:: section


   .. rubric:: Input Parameters
      :class: sectiontitle


   Buffer API:


   exec_queue
      The queue where the routine should be executed.


   n
      Specifies the number of elements to be calculated.


   a
      The buffer ``a`` containing input vector of size ``n``.


   mode
      Overrides the global VM mode setting for this function call. See
      :ref:`onemath_vm_setmode`
      function for possible values and their description. This is an
      optional parameter. The default value is ``oneapi::math::vm::mode::not_defined``.


   errhandler
      Sets local error handling mode for this function call. See the
      :ref:`onemath_vm_create_error_handler`
      function for arguments and their descriptions. This is an optional
      parameter. The local error handler is disabled by default.


   USM API:


   exec_queue
      The queue where the routine should be executed.


   n
      Specifies the number of elements to be calculated.


   a
      Pointer ``a`` to the input vector of size ``n``.


   depends
      Vector of dependent events (to wait for input data to be ready).


   mode
      Overrides the global VM mode setting for this function call. See
      the :ref:`onemath_vm_setmode`
      function for possible values and their description. This is an
      optional parameter. The default value is ``oneapi::math::vm::mode::not_defined``.


   errhandler
      Sets local error handling mode for this function call. See the
      :ref:`onemath_vm_create_error_handler`
      function for arguments and their descriptions. This is an optional
      parameter. The local error handler is disabled by default.


.. container:: section


   .. rubric:: Output Parameters
      :class: sectiontitle


   Buffer API:


   y
      The buffer ``y`` containing the output vector of size ``n``.


   USM API:


   y
      Pointer ``y`` to the output vector of size ``n``.


   return value (event)
      Event, signifying availability of computed output and status code(s).

.. container:: section


    .. rubric:: Exceptions
        :class: sectiontitle

    For list of generated exceptions please refer to  :ref:`onemath_vm_exceptions`


.. container:: familylinks


   .. container:: parentlink

      **Parent topic:** :ref:`onemath_vm_mathematical_functions`