NDArraySimilarity.cpp

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#include "NDArraySimilarity.h"
 
#include <cstddef>
#include <cmath>
 
namespace armarx::aron::similarity::variant::ndarray
{
    float
    calculateSimilarity(const aron::data::NDArray& oldValue, const aron::data::NDArray& newValue)
    {
        if (oldValue.getShape() != newValue.getShape())
        {
            return 0.0f;
        }
 
        const auto oldData = oldValue.getDataAsVector();
        const auto newData = newValue.getDataAsVector();
        if (oldData.size() != newData.size())
        {
            return 0.0f;
        }
 
        double dotProduct = 0.0;
        double oldSquaredSum = 0.0;
        double newSquaredSum = 0.0;
 
        for (size_t i = 0; i < oldData.size(); i++)
        {
            const double oldElement = static_cast<double>(oldData.at(i));
            const double newElement = static_cast<double>(newData.at(i));
 
            dotProduct += oldElement * newElement;
            oldSquaredSum += oldElement * oldElement;
            newSquaredSum += newElement * newElement;
        }
 
        const double normProduct = std::sqrt(oldSquaredSum) * std::sqrt(newSquaredSum);
        if (normProduct == 0.0)
        {
            return oldSquaredSum == newSquaredSum ? 1.0f : 0.0f;
        }
 
        const double cosineSimilarity = dotProduct / normProduct;
        const double normalizedSimilarity = (cosineSimilarity / 2.0) + 0.5;
 
        return static_cast<float>(normalizedSimilarity);
    }
}