From 6deda2531c8eb1d30a198ec6b4cdf54558731a6f Mon Sep 17 00:00:00 2001
From: Daniil Osokin <daniil.osokin@itseez.com>
Date: Mon, 4 Feb 2013 17:34:18 +0400
Subject: [PATCH 1/2] Fixed getNumThreads() for C=
---
modules/core/src/parallel.cpp | 6 ++++--
1 file changed, 4 insertions(+), 2 deletions(-)
diff --git a/modules/core/src/parallel.cpp b/modules/core/src/parallel.cpp
index 2bc8a0588..0b2a845ac 100644
--- a/modules/core/src/parallel.cpp
+++ b/modules/core/src/parallel.cpp
@@ -305,7 +305,9 @@ int cv::getNumThreads(void)
#elif defined HAVE_CSTRIPES
- return cv::getNumberOfCPUs();
+ return numThreads > 0
+ ? numThreads
+ : cv::getNumberOfCPUs();
#elif defined HAVE_OPENMP
@@ -491,4 +493,4 @@ CV_IMPL int cvGetNumThreads()
CV_IMPL int cvGetThreadNum()
{
return cv::getThreadNum();
-}
\ No newline at end of file
+}
From 5f32e0e24d33d2d3cd8169fcbb1126b8ec01a7c3 Mon Sep 17 00:00:00 2001
From: Daniil Osokin <daniil.osokin@itseez.com>
Date: Wed, 30 Jan 2013 10:38:31 +0400
Subject: [PATCH 2/2] Rewrote doc for set-get number of threads functionality
with support new frameworks (bug #2064)
---
...tility_and_system_functions_and_macros.rst | 63 +++++++++++++++----
1 file changed, 52 insertions(+), 11 deletions(-)
diff --git a/modules/core/doc/utility_and_system_functions_and_macros.rst b/modules/core/doc/utility_and_system_functions_and_macros.rst
index 861f98bfc..9055415f1 100644
--- a/modules/core/doc/utility_and_system_functions_and_macros.rst
+++ b/modules/core/doc/utility_and_system_functions_and_macros.rst
@@ -311,13 +311,34 @@ Returns true if the specified feature is supported by the host hardware.
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`,
@@ -326,16 +347,24 @@ The function returns the number of threads that is used by OpenCV.
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`
@@ -410,13 +439,25 @@ This operation is used in the simplest or most complex image processing function
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 nthreads)
+.. ocv:function:: void setNumThreads(int threads)
- :param nthreads: Number of threads used by OpenCV.
+ :param threads: Number of threads used by OpenCV.
-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.
+OpenCV will try to run it's functions with specified threads number, but
+some behaviour differs from framework:
+
+ * **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`,