PatternMatching/DistanceMetrics.h at master · briepala/PatternMatching · GitHub

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#ifndef PATTERNMATCHING_DISTANCEMETRICS_H
#define PATTERNMATCHING_DISTANCEMETRICS_H

#include <vector>
#include <cmath>
#include "Config.h"

namespace DistanceMetrics {

    using DistanceType = Config::DistanceType;

    inline double sad(const double* a, const double* b, size_t len);
    inline double sad_early_termination(const double* a, const double* b, size_t len, double threshold);
    inline double sad_simd(const double* a, const double* b, size_t len);

    inline double computeDistance(const double* a, const double* b, size_t length,
                              DistanceType type, double threshold = std::numeric_limits<double>::max()) {
        switch (type) {
            case DistanceType::SAD_BASIC:
                return sad(a, b, length);
            case DistanceType::SAD_EARLY_TERMINATION:
                return sad_early_termination(a, b, length, threshold);
            case DistanceType::SAD_SIMD:
                return sad_simd(a, b, length);
            default:
                return sad(a, b, length);
        }
    }

    inline double sad(const double* a, const double* b, size_t len) {
        double sum = 0.0;
        for (size_t i = 0; i < len; ++i) {
            sum += std::abs(a[i] - b[i]);
        }
        return sum;
    }

    inline double sad_early_termination(const double* a, const double* b,
                                         size_t len, double threshold) {
        double sum = 0.0;
        for (size_t i = 0; i < len; ++i) {
            sum += std::abs(a[i] - b[i]);
            if (sum > threshold) return sum;
        }
        return sum;
    }

    inline double sad_simd(const double* a, const double* b, size_t len) {
        double sum = 0.0;
#pragma omp simd reduction(+:sum)
        for (size_t i = 0; i < len; ++i) {
            sum += std::abs(a[i] - b[i]);
        }
        return sum;
    }

}

#endif //PATTERNMATCHING_DISTANCEMETRICS_H