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WIP: BUG: Remove std distribution from ConnectedComponentImageFilter tests #5836

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WIP: BUG: Remove std distribution from ConnectedComponentImageFilter tests #5836

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11 changes: 5 additions & 6 deletions Modules/Segmentation/ConnectedComponents/test/itkConnectedComponentImageFilterTest.cxx
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Original file line number Diff line number Diff line change
Expand Up @@ -125,18 +125,17 @@ itkConnectedComponentImageFilterTest(int argc, char * argv[])
std::vector<RGBPixelType> colormap;
colormap.resize(numObjects + 1);

using RGBComponentType = RGBPixelType::ComponentType;
constexpr auto maxRGBComponentValue = std::numeric_limits<RGBComponentType>::max();

constexpr std::mt19937::result_type randomSeed{ 1031571 };
std::mt19937 randomNumberEngine(randomSeed);
std::uniform_int_distribution<> randomNumberDistribution(maxRGBComponentValue / 3, maxRGBComponentValue);

for (auto & i : colormap)
{
RGBPixelType px;
std::generate(px.begin(), px.end(), [&randomNumberEngine, &randomNumberDistribution] {
return static_cast<RGBComponentType>(randomNumberDistribution(randomNumberEngine));
std::generate(px.begin(), px.end(), [&randomNumberEngine] {
using RGBComponentType = RGBPixelType::ComponentType;
constexpr uint32_t maxValue{ std::numeric_limits<RGBComponentType>::max() };
constexpr uint32_t minValue{ maxValue / 3 };
return static_cast<RGBComponentType>(randomNumberEngine() % (maxValue - minValue + 1) + minValue);
Comment on lines -133 to +138
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@N-Dekker N-Dekker Feb 27, 2026

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FYI, I just compared the result of this "manual" calculation with the result of std::uniform_int_distribution. It appears that both yield the same numbers on old versions of Visual C++ (VS2019). See https://godbolt.org/z/nYsvafs51

#include <iostream>
#include <random>

int main()
{
  constexpr uint32_t maxValue{ std::numeric_limits<unsigned char>::max() };
  constexpr uint32_t minValue{ maxValue / 3 };
  constexpr std::mt19937::result_type randomSeed{ 1031571 };

  int n = 7;
  {
    std::cout << "Using `std::uniform_int_distribution`:    ";
    std::mt19937 randomNumberEngine(randomSeed);
    std::uniform_int_distribution<> randomNumberDistribution(minValue, maxValue);

    for (int i{}; i < n; ++i)
    {
      std::cout << randomNumberDistribution(randomNumberEngine) << ' ';
    }
  }
  std::cout << std::endl;
  {
    std::cout << "Doing the calculation of the pull request: ";
    std::mt19937 randomNumberEngine(randomSeed);

    for (int i{}; i < n; ++i)
    {
      std::cout << (randomNumberEngine() % (maxValue - minValue + 1) + minValue) << ' ';
    }
    std::cout << std::endl;
  }
}

Output from msvc v19.34 VS17.4:

Using `std::uniform_int_distribution`:    119 221 168 148 91 249 122 
Doing the calculation of the pull request: 119 221 168 148 91 249 122

});

i = px;
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11 changes: 5 additions & 6 deletions Modules/Segmentation/ConnectedComponents/test/itkConnectedComponentImageFilterTestRGB.cxx
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Expand Up @@ -105,17 +105,16 @@ itkConnectedComponentImageFilterTestRGB(int argc, char * argv[])
RGBPixelType px;
colormap.resize(numObjects + 1);

using RGBComponentType = RGBPixelType::ComponentType;
constexpr auto maxRGBComponentValue = std::numeric_limits<RGBComponentType>::max();

constexpr std::mt19937::result_type randomSeed{ 1031571 };
std::mt19937 randomNumberEngine(randomSeed);
std::uniform_int_distribution<> randomNumberDistribution(maxRGBComponentValue / 3, maxRGBComponentValue);

for (auto & i : colormap)
{
std::generate(px.begin(), px.end(), [&randomNumberEngine, &randomNumberDistribution] {
return static_cast<RGBComponentType>(randomNumberDistribution(randomNumberEngine));
std::generate(px.begin(), px.end(), [&randomNumberEngine] {
using RGBComponentType = RGBPixelType::ComponentType;
constexpr uint32_t maxValue{ std::numeric_limits<RGBComponentType>::max() };
constexpr uint32_t minValue{ maxValue / 3 };
return static_cast<RGBComponentType>(randomNumberEngine() % (maxValue - minValue + 1) + minValue);
});

i = px;
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