ENH: Add SetDefaultNumberOfThreads

src/Core/Common/CMakeLists.txt

@@ -204,3 +204,5 @@ compare_to_baseline(EXAMPLE_NAME OutOfBoundsPixelsReturnConstValue
   BASELINE_PREFIX OutputBaseline
   )
 endif()
+
+add_example(SetDefaultNumberOfThreads)

src/Core/Common/SetDefaultNumberOfThreads/CMakeLists.txt

@@ -0,0 +1,36 @@
+cmake_minimum_required(VERSION 3.10.2)
+
+project(SetDefaultNumberOfThreads)
+
+find_package(ITK REQUIRED)
+include(${ITK_USE_FILE})
+
+add_executable(SetDefaultNumberOfThreads Code.cxx)
+target_link_libraries(SetDefaultNumberOfThreads ${ITK_LIBRARIES})
+
+install(TARGETS SetDefaultNumberOfThreads
+  DESTINATION bin/ITKExamples/Core/Common
+  COMPONENT Runtime
+)
+
+install(FILES Code.cxx CMakeLists.txt Code.py
+  DESTINATION share/ITKExamples/Code/Core/Common/SetDefaultNumberOfThreads
+  COMPONENT Code
+)
+
+enable_testing()
+
+set(test_options 3)
+
+add_test(NAME SetDefaultNumberOfThreadsTest
+  COMMAND ${CMAKE_RUNTIME_OUTPUT_DIRECTORY}/SetDefaultNumberOfThreads
+  ${test_options}
+)
+
+if(ITK_WRAP_PYTHON)
+  find_package(PythonInterp REQUIRED)
+  add_test( NAME SetDefaultNumberOfThreadsTestPython
+    COMMAND ${PYTHON_EXECUTABLE} ${CMAKE_CURRENT_SOURCE_DIR}/Code.py
+      ${test_options}
+    )
+endif()

src/Core/Common/SetDefaultNumberOfThreads/Code.cxx

@@ -0,0 +1,53 @@
+/*=========================================================================
+ *
+ *  Copyright Insight Software Consortium
+ *
+ *  Licensed under the Apache License, Version 2.0 (the "License");
+ *  you may not use this file except in compliance with the License.
+ *  You may obtain a copy of the License at
+ *
+ *         http://www.apache.org/licenses/LICENSE-2.0.txt
+ *
+ *  Unless required by applicable law or agreed to in writing, software
+ *  distributed under the License is distributed on an "AS IS" BASIS,
+ *  WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ *  See the License for the specific language governing permissions and
+ *  limitations under the License.
+ *
+ *=========================================================================*/
+#include "itkMultiThreaderBase.h"
+#include "itkMedianImageFilter.h"
+
+int
+main(int argc, char * argv[])
+{
+  if (argc != 2)
+  {
+    std::cerr << "Usage: " << std::endl;
+    std::cerr << argv[0];
+    std::cerr << " <NumberOfThreads>";
+    std::cerr << std::endl;
+    return EXIT_FAILURE;
+  }
+
+  const auto numberOfThreads = std::atoi(argv[1]);
+
+  itk::MultiThreaderBase::SetGlobalDefaultNumberOfThreads(numberOfThreads);
+
+  constexpr unsigned int Dimension = 2;
+  using PixelType = float;
+  using ImageType = itk::Image<PixelType, Dimension>;
+  using FilterType = itk::MedianImageFilter<ImageType, ImageType>;
+  FilterType::Pointer filter = FilterType::New();
+
+  const auto filterDefaultThreads = filter->GetMultiThreader()->GetGlobalDefaultNumberOfThreads();
+  std::cout << "Filter's default number of threads: " << filterDefaultThreads << std::endl;
+
+  if (filterDefaultThreads != numberOfThreads)
+  {
+    std::cerr << "Filter does not have expected default number of threads." << std::endl;
+    return EXIT_FAILURE;
+  }
+
+  return EXIT_SUCCESS;
+}

src/Core/Common/SetDefaultNumberOfThreads/Code.py

@@ -0,0 +1,33 @@
+#!/usr/bin/env python
+
+# Copyright Insight Software Consortium
+#
+# Licensed under the Apache License, Version 2.0 (the "License");
+# you may not use this file except in compliance with the License.
+# You may obtain a copy of the License at
+#
+#        http://www.apache.org/licenses/LICENSE-2.0.txt
+#
+# Unless required by applicable law or agreed to in writing, software
+# distributed under the License is distributed on an "AS IS" BASIS,
+# WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+# See the License for the specific language governing permissions and
+# limitations under the License.
+
+import argparse
+import itk
+
+parser = argparse.ArgumentParser(description='Set the Default Number Of Threads.')
+parser.add_argument('number_of_threads', type=int)
+args = parser.parse_args()
+
+# Create a MultiThreaderBase instance to get access to its static methods
+threader = itk.MultiThreaderBase.New()
+threader.SetGlobalDefaultNumberOfThreads(args.number_of_threads)
+
+filt = itk.MedianImageFilter.New()
+filter_default_threads = filt.GetMultiThreader().GetGlobalDefaultNumberOfThreads()
+
+print("Filter's default number of threads: {}".format(filter_default_threads))
+
+assert(filter_default_threads == args.number_of_threads)

src/Core/Common/SetDefaultNumberOfThreads/Documentation.rst

@@ -0,0 +1,46 @@
+Set the Default Number Of Threads
+=================================
+
+.. index::
+   single: MultiThreaderBase
+
+Synopsis
+--------
+
+Set the default number of threads for multi-threading.
+
+The default number of threads can also be set via the environment variable,
+`ITK_GLOBAL_DEFAULT_NUMBER_OF_THREADS`.
+
+
+Results
+-------
+
+Output::
+
+  Filter's default number of threads: 3
+
+
+
+Code
+----
+
+C++
+...
+
+.. literalinclude:: Code.cxx
+   :language: c++
+   :lines: 18-
+
+Python
+......
+
+.. literalinclude:: Code.py
+   :language: python
+   :lines: 1,18-
+
+
+Classes demonstrated
+--------------------
+
+.. breathelink:: itk::MultiThreaderBase

src/Core/Common/index.rst

@@ -110,4 +110,5 @@ Common
   StoreNonPixelDataInImage/Documentation.rst
   CheckIfModuleIsPresent/Documentation.rst
   DisplayImage/Documentation.rst
-  DirectWarningToFile/Documentation.rst
+  DirectWarningToFile/Documentation.rst
+  SetDefaultNumberOfThreads/Documentation.rst