From c3dd02c2c674bd8db0788b82a9ca933981bd43e8 Mon Sep 17 00:00:00 2001
From: Niels Dekker <N.Dekker@lumc.nl>
Date: Thu, 25 Aug 2022 21:23:37 +0200
Subject: [PATCH] ENH: Add `NumberOfThreads` property to itk::TransformixFilter

Addressed issue https://github.com/InsightSoftwareConsortium/ITKElastix/issues/163 "No option to set number of threads for Transformix", submitted by Sebastian van der Voort.
---
 .../GTesting/itkTransformixFilterGTest.cxx    | 42 +++++++++++++++++++
 Core/Main/itkTransformixFilter.h              |  5 +++
 Core/Main/itkTransformixFilter.hxx            |  5 +++
 3 files changed, 52 insertions(+)

diff --git a/Core/Main/GTesting/itkTransformixFilterGTest.cxx b/Core/Main/GTesting/itkTransformixFilterGTest.cxx
index c17476058..bfbff6132 100644
--- a/Core/Main/GTesting/itkTransformixFilterGTest.cxx
+++ b/Core/Main/GTesting/itkTransformixFilterGTest.cxx
@@ -63,6 +63,7 @@ using ParameterValuesType = itk::ParameterFileParser::ParameterValuesType;
 
 // Using-declarations:
 using elx::CoreMainGTestUtilities::CheckNew;
+using elx::CoreMainGTestUtilities::CreateImage;
 using elx::CoreMainGTestUtilities::CreateImageFilledWithSequenceOfNaturalNumbers;
 using elx::CoreMainGTestUtilities::Deref;
 using elx::CoreMainGTestUtilities::DerefSmartPointer;
@@ -445,6 +446,47 @@ GTEST_TEST(itkTransformixFilter, IsDefaultInitialized)
   EXPECT_FALSE(transformixFilter.GetLogToConsole());
   EXPECT_FALSE(transformixFilter.GetLogToFile());
   EXPECT_EQ(transformixFilter.GetOutputMesh(), nullptr);
+  EXPECT_EQ(transformixFilter.GetNumberOfThreads(), 0);
+}
+
+
+GTEST_TEST(itkTransformixFilter, NumberOfThreadsEqualsGlobalMaximumNumberOfThreads)
+{
+  constexpr auto ImageDimension = 2U;
+  using PixelType = float;
+  using ImageType = itk::Image<PixelType, ImageDimension>;
+  using TransformixFilterType = itk::TransformixFilter<ImageType>;
+
+  elx::DefaultConstruct<TransformixFilterType> transformixFilter;
+
+  constexpr auto imageSize = ImageType::SizeType::Filled(1);
+  const auto     image = CreateImage<PixelType>(imageSize);
+
+  transformixFilter.SetMovingImage(image);
+  transformixFilter.SetTransformParameterObject(
+    CreateParameterObject({ // Parameters in alphabetic order:
+                            { "Direction", CreateDefaultDirectionParameterValues<ImageDimension>() },
+                            { "Index", ParameterValuesType(ImageDimension, "0") },
+                            { "NumberOfParameters", { std::to_string(ImageDimension) } },
+                            { "Origin", ParameterValuesType(ImageDimension, "0") },
+                            { "ResampleInterpolator", { "FinalLinearInterpolator" } },
+                            { "Size", ConvertToParameterValues(imageSize) },
+                            { "Transform", ParameterValuesType{ "TranslationTransform" } },
+                            { "TransformParameters", ParameterValuesType(ImageDimension, "0") },
+                            { "Spacing", ParameterValuesType(ImageDimension, "1") } }));
+
+  const auto initialGlobalMaximumNumberOfThreads = itk::MultiThreaderBase::GetGlobalMaximumNumberOfThreads();
+  ASSERT_GE(initialGlobalMaximumNumberOfThreads, 1);
+  ASSERT_LE(initialGlobalMaximumNumberOfThreads, itk::ITK_MAX_THREADS);
+
+  for (const int numberOfThreads :
+       { 1, 2, int{ itk::ITK_MAX_THREADS }, static_cast<int>(initialGlobalMaximumNumberOfThreads) })
+  {
+    transformixFilter.SetNumberOfThreads(numberOfThreads);
+    ASSERT_EQ(transformixFilter.GetNumberOfThreads(), numberOfThreads);
+    transformixFilter.Update();
+    EXPECT_EQ(itk::MultiThreaderBase::GetGlobalMaximumNumberOfThreads(), numberOfThreads);
+  }
 }
 
 
diff --git a/Core/Main/itkTransformixFilter.h b/Core/Main/itkTransformixFilter.h
index 42972df0f..5c190fe08 100644
--- a/Core/Main/itkTransformixFilter.h
+++ b/Core/Main/itkTransformixFilter.h
@@ -200,6 +200,9 @@ class ITK_TEMPLATE_EXPORT TransformixFilter : public ImageSource<TMovingImage>
     m_EnableOutput = false;
   }
 
+  itkSetMacro(NumberOfThreads, int);
+  itkGetConstMacro(NumberOfThreads, int);
+
   /** Sets an (optional) input mesh. An Update() will transform its points, and store them in the output mesh.  */
   void
   SetInputMesh(typename MeshType::ConstPointer mesh)
@@ -264,6 +267,8 @@ class ITK_TEMPLATE_EXPORT TransformixFilter : public ImageSource<TMovingImage>
   bool m_LogToConsole{ false };
   bool m_LogToFile{ false };
 
+  int m_NumberOfThreads{ 0 };
+
   typename MeshType::ConstPointer m_InputMesh{ nullptr };
   typename MeshType::Pointer      m_OutputMesh{ nullptr };
 };
diff --git a/Core/Main/itkTransformixFilter.hxx b/Core/Main/itkTransformixFilter.hxx
index 9d07ceecf..6294c391c 100644
--- a/Core/Main/itkTransformixFilter.hxx
+++ b/Core/Main/itkTransformixFilter.hxx
@@ -146,6 +146,11 @@ TransformixFilter<TMovingImage>::GenerateData()
     }
   }
 
+  if (m_NumberOfThreads > 0)
+  {
+    argumentMap.insert(ArgumentMapEntryType("-threads", std::to_string(m_NumberOfThreads)));
+  }
+
   // Setup xout
   const auto manager = m_EnableOutput
                          ? std::make_unique<const elx::xoutManager>(logFileName, m_LogToFile, m_LogToConsole)