From 997ff54d59335b3dc55ff54e8175c9050a84a3c3 Mon Sep 17 00:00:00 2001
From: Niels Dekker <N.Dekker@lumc.nl>
Date: Sat, 2 Sep 2023 01:20:03 +0200
Subject: [PATCH] BUG: ImageRandomIteratorWithIndex should not assign data in
 constructor

The constructors of `ImageRandomConstIteratorWithIndex` and
`ImageRandomConstIteratorWithOnlyIndex` that support two arguments (image and
region) accidentally still assigned their data members, while they were already
initialized by in-class default member initialization. This in-class default
member initialization was added as part of pull request
https://github.com/InsightSoftwareConsortium/ITK/pull/3929 commit
4e46cb6ef56658353c14bd58e6b28b63c410f1c8 "STYLE: Default default-constructor of
ImageRandom ConstIterator classes", merged on February 24, 2023 and included
with tag ITK v5.4rc01.

This caused extra `MersenneTwisterRandomVariateGenerator::New()` calls, which
changed the seeds of random number generation. These changes can possibly cause
regression failures in unit tests of client applications, including elastix.

This commit removes all data member assignments from the bodies of these
constructors.
---
 .../include/itkImageRandomConstIteratorWithIndex.hxx      | 8 ++------
 .../include/itkImageRandomConstIteratorWithOnlyIndex.hxx  | 8 ++------
 2 files changed, 4 insertions(+), 12 deletions(-)

diff --git a/Modules/Core/Common/include/itkImageRandomConstIteratorWithIndex.hxx b/Modules/Core/Common/include/itkImageRandomConstIteratorWithIndex.hxx
index 152166c669a..5295a2b7c8d 100644
--- a/Modules/Core/Common/include/itkImageRandomConstIteratorWithIndex.hxx
+++ b/Modules/Core/Common/include/itkImageRandomConstIteratorWithIndex.hxx
@@ -26,12 +26,8 @@ template <typename TImage>
 ImageRandomConstIteratorWithIndex<TImage>::ImageRandomConstIteratorWithIndex(const ImageType *  ptr,
                                                                              const RegionType & region)
   : ImageConstIteratorWithIndex<TImage>(ptr, region)
-{
-  m_NumberOfPixelsInRegion = region.GetNumberOfPixels();
-  m_NumberOfSamplesRequested = 0L;
-  m_NumberOfSamplesDone = 0L;
-  m_Generator = Statistics::MersenneTwisterRandomVariateGenerator::New();
-}
+  , m_NumberOfPixelsInRegion{ region.GetNumberOfPixels() }
+{}
 
 template <typename TImage>
 void
diff --git a/Modules/Core/Common/include/itkImageRandomConstIteratorWithOnlyIndex.hxx b/Modules/Core/Common/include/itkImageRandomConstIteratorWithOnlyIndex.hxx
index 309b0974f2e..fffea4e9941 100644
--- a/Modules/Core/Common/include/itkImageRandomConstIteratorWithOnlyIndex.hxx
+++ b/Modules/Core/Common/include/itkImageRandomConstIteratorWithOnlyIndex.hxx
@@ -26,12 +26,8 @@ template <typename TImage>
 ImageRandomConstIteratorWithOnlyIndex<TImage>::ImageRandomConstIteratorWithOnlyIndex(const ImageType *  ptr,
                                                                                      const RegionType & region)
   : ImageConstIteratorWithOnlyIndex<TImage>(ptr, region)
-{
-  m_NumberOfPixelsInRegion = region.GetNumberOfPixels();
-  m_NumberOfSamplesRequested = 0L;
-  m_NumberOfSamplesDone = 0L;
-  m_Generator = Statistics::MersenneTwisterRandomVariateGenerator::New();
-}
+  , m_NumberOfPixelsInRegion{ region.GetNumberOfPixels() }
+{}
 
 template <typename TImage>
 void