The function returns true if the host hardware supports the specified feature. When user calls ``setUseOptimized(false)``, the subsequent calls to ``checkHardwareSupport()`` will return false until ``setUseOptimized(true)`` is called. This way user can dynamically switch on and off the optimized code in OpenCV.
+
+
+getNumberOfCPUs
+-----------------
+Returns the number of logical CPUs available for the process.
+
+.. ocv:function:: int getNumberOfCPUs()
+
+
+
getNumThreads
--------------
-Returns the number of threads used by OpenCV.
+-----------------
+Returns the number of threads used by OpenCV for parallel regions.
+Always returns 1 if OpenCV is built without threading support.
.. ocv:function:: int getNumThreads()
-The function returns the number of threads that is used by OpenCV.
+The exact meaning of return value depends on the threading framework used by OpenCV library:
+
+ * **TBB** – The number of threads, that OpenCV will try to use for parallel regions.
+ If there is any ``tbb::thread_scheduler_init`` in user code conflicting with OpenCV, then
+ function returns default number of threads used by TBB library.
+ * **OpenMP** – An upper bound on the number of threads that could be used to form a new team.
+ * **Concurrency** – The number of threads, that OpenCV will try to use for parallel regions.
+ * **GCD** – Unsupported; returns the GCD thread pool limit (512) for compatibility.
+ * **C=** – The number of threads, that OpenCV will try to use for parallel regions,
+ if before called ``setNumThreads`` with ``threads > 0``,
+ otherwise returns the number of logical CPUs, available for the process.
.. seealso::
:ocv:func:`setNumThreads`,
getThreadNum
-------------
-Returns the index of the currently executed thread.
+----------------
+Returns the index of the currently executed thread within the current parallel region.
+Always returns 0 if called outside of parallel region.
.. ocv:function:: int getThreadNum()
-The function returns a 0-based index of the currently executed thread. The function is only valid inside a parallel OpenMP region. When OpenCV is built without OpenMP support, the function always returns 0.
+The exact meaning of return value depends on the threading framework used by OpenCV library:
+
+ * **TBB** – Unsupported with current 4.1 TBB release. May be will be supported in future.
+ * **OpenMP** – The thread number, within the current team, of the calling thread.
+ * **Concurrency** – An ID for the virtual processor that the current context is executing
+ on (0 for master thread and unique number for others, but not necessary 1,2,3,...).
+ * **GCD** – System calling thread's ID. Never returns 0 inside parallel region.
+ * **C=** – The index of the current parallel task.
.. seealso::
:ocv:func:`setNumThreads`,
- :ocv:func:`getNumThreads` .
+ :ocv:func:`getNumThreads`
setNumThreads
-----------------
-Sets the number of threads used by OpenCV.
+OpenCV will try to set the number of threads for the next parallel region.
+If ``threads == 0``, OpenCV will disable threading optimizations and run all it's
+functions sequentially. Passing ``threads < 0`` will reset threads number to system default.
+This function must be called outside of parallel region.
+
+.. ocv:function:: void setNumThreads(int threads)
-.. ocv:function:: void setNumThreads(int nthreads)
+ :param threads: Number of threads used by OpenCV.
- :param nthreads: Number of threads used by OpenCV.
+OpenCV will try to run it's functions with specified threads number, but
+some behaviour differs from framework:
-The function sets the number of threads used by OpenCV in parallel OpenMP regions. If ``nthreads=0`` , the function uses the default number of threads that is usually equal to the number of the processing cores.
+ * **TBB** – User-defined parallel constructions will run with the same threads number,
+ if another does not specified. If late on user creates own scheduler, OpenCV will be use it.
+ * **OpenMP** – No special defined behaviour.
+ * **Concurrency** – If ``threads == 1``, OpenCV will disable threading optimizations
+ and run it's functions sequentially.
+ * **GCD** – Supports only values <= 0.
+ * **C=** – No special defined behaviour.
.. seealso::
:ocv:func:`getNumThreads`,