opencv/modules/gpu/doc/initalization_and_information.rst

Initalization and Information
=============================

.. highlight:: cpp

.. index:: gpu::getCudaEnabledDeviceCount

cv::gpu::getCudaEnabledDeviceCount
----------------------------------
.. c:function:: int getCudaEnabledDeviceCount()

    Returns number of CUDA-enabled devices installed. It is to be used before any other GPU functions calls. If OpenCV is compiled without GPU support this function returns 0.

.. index:: gpu::setDevice

cv::gpu::setDevice
------------------
.. c:function:: void setDevice(int device)

    Sets device and initializes it for the current thread. Call of this function can be omitted, but in this case a default device will be initialized on fist GPU usage.

    :param device: index of GPU device in system starting with 0.

.. index:: gpu::getDevice

cv::gpu::getDevice
------------------
.. c:function:: int getDevice()

    Returns the current device index, which was set by {gpu::getDevice} or initialized by default.

.. index:: gpu::GpuFeature

.. _gpu::GpuFeature:

gpu::GpuFeature
---------------
.. c:type:: gpu::GpuFeature

GPU compute features. ::

    enum GpuFeature
    {
        COMPUTE_10, COMPUTE_11,
        COMPUTE_12, COMPUTE_13,
        COMPUTE_20, COMPUTE_21,
        ATOMICS, NATIVE_DOUBLE
    };


.. index:: gpu::DeviceInfo

.. _gpu::DeviceInfo:

gpu::DeviceInfo
---------------
.. c:type:: gpu::DeviceInfo

This class provides functionality for querying the specified GPU properties. ::

    class CV_EXPORTS DeviceInfo
    {
    public:
        DeviceInfo();
        DeviceInfo(int device_id);

        string name() const;

        int majorVersion() const;
        int minorVersion() const;

        int multiProcessorCount() const;

        size_t freeMemory() const;
        size_t totalMemory() const;

        bool supports(GpuFeature feature) const;
        bool isCompatible() const;
    };


.. index:: gpu::DeviceInfo::DeviceInfo

cv::gpu::DeviceInfo::DeviceInfo
------------------------------- ``_``
.. c:function:: DeviceInfo::DeviceInfo()

.. c:function:: DeviceInfo::DeviceInfo(int device_id)

    Constructs DeviceInfo object for the specified device. If deviceidparameter is missed it constructs object for the current device.

    :param device_id: Index of the GPU device in system starting with 0.

.. index:: gpu::DeviceInfo::name

cv::gpu::DeviceInfo::name
-------------------------
.. c:function:: string DeviceInfo::name()

    Returns the device name.

.. index:: gpu::DeviceInfo::majorVersion

cv::gpu::DeviceInfo::majorVersion
---------------------------------
.. c:function:: int DeviceInfo::majorVersion()

    Returns the major compute capability version.

.. index:: gpu::DeviceInfo::minorVersion

cv::gpu::DeviceInfo::minorVersion
---------------------------------
.. c:function:: int DeviceInfo::minorVersion()

    Returns the minor compute capability version.

.. index:: gpu::DeviceInfo::multiProcessorCount

cv::gpu::DeviceInfo::multiProcessorCount
----------------------------------------
.. c:function:: int DeviceInfo::multiProcessorCount()

    Returns the number of streaming multiprocessors.

.. index:: gpu::DeviceInfo::freeMemory

cv::gpu::DeviceInfo::freeMemory
-------------------------------
.. c:function:: size_t DeviceInfo::freeMemory()

    Returns the amount of free memory in bytes.

.. index:: gpu::DeviceInfo::totalMemory

cv::gpu::DeviceInfo::totalMemory
--------------------------------
.. c:function:: size_t DeviceInfo::totalMemory()

    Returns the amount of total memory in bytes.

.. index:: gpu::DeviceInfo::supports

cv::gpu::DeviceInfo::supports
-----------------------------
.. c:function:: bool DeviceInfo::supports(GpuFeature feature)

    Returns true if the device has the given GPU feature, otherwise false.

    :param feature: Feature to be checked. See  .

.. index:: gpu::DeviceInfo::isCompatible

cv::gpu::DeviceInfo::isCompatible
---------------------------------
.. c:function:: bool DeviceInfo::isCompatible()

    Returns true if the GPU module can be run on the specified device, otherwise false.

.. index:: gpu::TargetArchs

.. _gpu::TargetArchs:

gpu::TargetArchs
----------------
.. c:type:: gpu::TargetArchs

This class provides functionality (as set of static methods) for checking which NVIDIA card architectures the GPU module was built for.

bigskip
The following method checks whether the module was built with the support of the given feature:

.. c:function:: static bool builtWith(GpuFeature feature)

    :param feature: Feature to be checked. See  .

There are a set of methods for checking whether the module contains intermediate (PTX) or binary GPU code for the given architecture(s):

.. c:function:: static bool has(int major, int minor)

.. c:function:: static bool hasPtx(int major, int minor)

.. c:function:: static bool hasBin(int major, int minor)

.. c:function:: static bool hasEqualOrLessPtx(int major, int minor)

.. c:function:: static bool hasEqualOrGreater(int major, int minor)

.. c:function:: static bool hasEqualOrGreaterPtx(int major, int minor)

.. c:function:: static bool hasEqualOrGreaterBin(int major, int minor)

    * **major** Major compute capability version.

    * **minor** Minor compute capability version.

According to the CUDA C Programming Guide Version 3.2: "PTX code produced for some specific compute capability can always be compiled to binary code of greater or equal compute capability".